# High speed CNC spindle



## mu38&Bg#

So it's time to replace the spindle in my Ebay parts CNC mill. I work on mostly small parts with 1/4" and under cutters so I decided on a fairly high RPM design using a brushless motor from the RC world to drive it. I have an industrial type controller but rated at only 500W, so I may just use an RC speed controller to operate it initially. I began today with the hope of getting along quick, but so far have made only a small dent in it.

An almost perfectly good motor was stripped down to the parts I need.


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## mu38&Bg#

If you haven't sawed through 2.25" 304SS round bar by hand you haven't lived! After a lot of sweat, I have a 6" long stick of said material in the chuck and will begin cutting some parts. As I was already thinking about surface finish, I did some tests the on OD of the bar. Steel inserts work OK, but for the finish pass I decided to try an aluminum insert. All I can say is the finish is much better than I expected and it take off as little as you want. This should work very well for finishing the bearing bores.

I'll post a sketch of the overall layout later.


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## stevehuckss396

Looking forward to it. I have thought of the same thing. I bought 3 - 15,000rpm motors and thats as far as i got.


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## pete

I'll be the first to admit I know less than nothing about computers or CNC, But if you haven't already thought of it I'd design and build your spindle to allow the use of some of the smaller series of ER collets. Obviously balance and dead true running will be a requirement at those speeds. Are the bearings your using designed to take the side and end forces?

Pete


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## mu38&Bg#

The design uses a pair of angular contact ball bearings in the bottom and a single angular contact bearing in the top. The tool holder is a Chinese ER16 straight shank holder. Motor is a Neu Motors 1912/1Y. The rest is going to be made. There are a few threads over at CNCzone that get into the design aspects. This is what it will look like.


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## Ken I

That's the way a spindle should be made - with two close coupled bearings as close as possible to the load and set to take out longitudinal lash - the tail end bearing merely acts as an outrigger to support and allow expansion and contraction of the spindle.

A common design error (my Chinese lathe and minimill) place the bearings at opposite ends of the spindle - so if set to zero lash - then as the spindle heats up it loads the bearings rapidly wearing them and introducing lash at stabilised temperatures once again.

Some industrial NC machines (Gildermeister) use angular contact tandem pairs which require unbelievable precision for both to carry the load.

2c - Ken


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## Simon0362

dieselpilot,

Some thoughts based on my own current experience of building a CNC HS spindle:


[liHow do you intend to hold the spindle - this is the 'right' moment to build in lugs, ears, or any other type of attachment - having a near perfect run out but a wobbly or not truely aligned spindle is not helpful]
your base design which puts the motor at the back - if you move the motor to the middle and move the top bearing to the very end, you will have a stiffer spindle assembly for side loads
 if you use a RC speed controller prepare to do some electronics to make it compatible with Mach3 - the servo/RC controllers expect a 1-2ms pulse every 20ms where 1ms = no speed and 2ms = full speed, whereas Mach3 outputs a true PWM signal where 0.2ms = zero and 19.5ms = full speed. The two are not compatible and require some playing to get them to work together

Power supply - I am currently (for testing) using a small car battery to provide enough amps to drive my ~500W outrunner since the power supplies I own did not like the peak start current - even with lots of C to help

I am watching your progress with interest and may even get around to reporting my own progress here...
Simon
[/list]


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## Dave G

A few years ago I picked up a Myford OD grinder that was missing the workhead. I built a workhead spindle from scratch and it has worked well so far. I agree with KenI that there should be 2 angular contact bearings on the tool end next to each other to set end play and 1 bearing on the other end as support for the spindle. Some high strength spindles use more than 2 bearings on the tool end but that is probably over kill. 
 One of the toughest jobs is to machine the bores for the outer races true to each other. The tool end will be bored for the 2 angular contact bearings and the other end of the housing will get bored for the support bearing. These bores and their shoulders must be true with each other. Any misalignment will create heat when running and assembly problems. I think maybe you could rough bore the housing first then fit it to an arbor between centers to finish each ends bores to keep alignment. I am quite interested in this project as I would like to do the same so keep us posted. my 2c, Dave


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## mu38&Bg#

Yes, I understand I have a bit of compromise by putting the motor on the end. I had a version drawn with the motor in the middle, but it complicated the components and assembly quite a bit. This makes it easier to build as the body is only ~90mm long. Chances are this would never see a 3/8" endmill except for light facing. Mounting on the machine will be the typical method for such spindles, a bored block with screws to clamp. The intention is to complete this in the next day or two.

Bearing suppliers tech specs describe numerous ways to assemble spindles. I agree though that is thermal expansion is not accounted for in material selection, a rigid system like Ken describes is bound to fail.

Back to the shop!


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## mu38&Bg#

I had a battle the PC today. I didn't print the drawings yesterday and it wouldn't boot today. Nothing new the PS for this particular Dell is trash I have 3 bad ones now. I was swapping 2 everytime they went down for some reason after a while resting they would work again. After days or weeks, after shutting down it won't give a "Power OK" signal after POST. So, today I fixed it semi-permanently by rewiring an ATX PS to meet the proprietary Dell connector standard. The only thing I don't have is fan tach signal from the PS. It runs with an error on boot, so I'm not going to complain for now.

Anyhow, I only manage to get the cone for the spindle shaft made today. Photos tomorrow after I get it mounted on the shaft and finish turned. Turning that 304SS is slow going.


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## Jeremy_BP

I'm really looking forward to seeing how this comes out. I'm currently in the process of looking at spindle options for mt CNC build, and have been eying those ER16 chucks. What size controller do you plan on using?


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## John S

Same here but I'm looking at something with speeds from 4,000 up to 10,000 max but enough power to poke a 5mm drill thru 6mm of steel.
Does this sound too unreasonable ?

John S.


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## mu38&Bg#

If you need torque, a reduction stage is probably necessary. I've seen a few spindles made from "outrunner" motors, which would have 2-3 times the torque of what I'm using, but I'm unsure of their capabilities. I looked at some machining power calculations before proceeding with this. I've been meaning to put it into a spreadsheet, but there are online calculators available.

http://www.mapal.us/res_calculators.html

I have an early start today, so should have some parts by dinner.


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## Swede

Dieselpilot, I'm curious, why did you reject the numerous eBay spindles that come in various power ratings, from 500W to 3kw? They seem to be a bargain. I wish they had been around years ago when I was struggling to find a suitable spindle for my own CNC build. In the end, I tried two different spindles - a Sherline ER-16 spindle, and the better answer, an eBay-purchased KaVo HF spindle.

Anyway, the spindles available that I refer to... here's a typical one:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=180662235123#ht_10291wt_1139

Even if you want more precision, something like this could be a "kit" of parts capable of being upgraded with ease.


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## mu38&Bg#

I remember your build of the little mill. It's why mine exists today. I've looked at those ebay spindles and thought pretty hard. I've heard that the aren't up to milling. One of the listings for Chinese spindles clearly states it's not for metal. Some time ago the same seller recommended them for cutting metal. They are a bit lacking in specs. The only step I'm really concerned about is balancing this thing. I don't know, maybe I'm digging a big hole. It might not work, it won't be the first time. Only one way to find out.

I forgot to verify the ID of the cone before cutting it off the bar. There was a bit of taper and need to be fixed. I decided to make a lap so that took up some time today. The cone was a shrink fit on the shaft, but I augmented it with anaerobic bearing mount. After it was on the shaft I did the finish passes to true it to the shaft. I have to put a 6 jaw set true chuck on my shopping list. I also made the bearing clamp. Hope for smooth sailing tomorrow with the body. That will be done in machined soft jaws.

Greg


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## mu38&Bg#

Progress was slow today. The nose bearing bore is almost done. Then the body gets turned around and put in the soft jaws I mentioned to machine the other end. If everything goes well, it should be dead nuts. All I had for my big boring bar were aluminum inserts. They work well at low feed rates. Some of the steel inserts out there have fairly high rake. 

Greg


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## mu38&Bg#

Well, I backed myself into a corner. I thought my dial bore gage reached to 1.75" but it's a 1.5". I can't get a consistent reading on a telescoping bore gage to see what my bearing bore is like. I might have to wait until I can beg, borrow, or :'( buy! a dial bore gage.


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## petertha

Swede  said:
			
		

> ...numerous eBay spindles that come in various power ratings



Sorry for the off topic, but your ebay link was very interesting. I had no idea those were available at that price. Do you think spindle / power box/vfd combo's like this would be adaptable as mini tool post grinders like for use on lathes? Im guessing the loads would be similar (or lighter?) than what it would see in CNC-mill plunging & routing, no?


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## Swede

Petertha - having no experience with these inexpensive eBay spindles, I'm a bit hesitant to say "go for it," but the price is soooo right. These things replicate unitary 3-phase HF (high frequency) spindles in appearance if not function. A German or similar HF spindle with similar characteristics (up to 50,000 RPM, ER nose, 0-400 hertz) would easily run $3,000 U.S. or more, possibly much more.

If you do want to give it a try, I'd go with an air-cooled variety, fabricate a guard for the wheel, and above all, be sure you use good wheels and balance them well. At 20,000 to 30,000 RPM, even tiny imbalances would shake it like crazy and possibly cause damage.

My gut feel says they'd do good work as a grinder spindle. Be aware that these bodies are pretty hefty diameter wise, so you'd have to also fabricate a mount. Using pullies and a belt would defeat the purpose, as you'd need another precision spindle for the wheel portion. Anyway, if you try one, it'd be very interesting.

Greg - Your components are looking very nice. Odd that your telescoping bore gauges aren't working for you. I assume the bore is for the bearing OD? What tolerances are you seeking? Have you considered sneaking up on the bore you need using the actual bearing as a gauge?


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## warranator

I have one of these spindles on my home CNC router. Mine is the 2.2kw version which holds an er20 collet. Don't expect much out of these cheap Chinese spindles, mine has a run out of 0.04mm so I am hesitant to run it at full speed with a smaller cutter. The bearings are far from being any German or even Japanese brands and more like Chinese crappy second grade bearings but they are replaceable, there is a thread some where on CNC zone on how to dismantle the spindle. The vfd are hit and miss whether they are missing certain components inside, some were made without the components to activate the on and off control coming from the pc, probably not a biggy to some. I will say one good thing, I bought mine to reduce the noise in my shed, sometimes the router can be running for 5 hours doing an engraving and the noise of a electric router will eventually drive you mad but this spindle is very quiet.


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## mu38&Bg#

My concern is mostly whether or not I have taper in the main bearing bore. I've fit bearing bore to said bearings but I don't want touch these bearings until they are ready to be installed. They are high speed spindle bearings. The plan is to shrink fit the bearing, which is easy, but the tech spec calls for +4/-3micron on the diameter. I can't claim to be that good, but I'm going to try to get close. Right now i've left plenty of material to practice. The telescoping gage is tricky to use, I might try polishing the ends before giving up on it.


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## Swede

One method you may want to consider with the telescoping gauge is to take a number of readings, say 6, toss out the high and low, and average the rest. That may not get you where you want to go, but it should be darned close.

The best internal bore gauge I've ever used is one of those three-point, carbide-anviled internal bore micrometers. When I needed 12 bores lapped to 1.0000", the thought of using telescoping gauges for that was not appealing, so I bought a 0.800" to 1.000" bore mike. But they are SO expensive.

Maybe someone has had some experience with one of those less-expensive bore gauge kits that use a dial... I think they are used mostly by guys boring IC engine cylinders.


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## mu38&Bg#

I did just buy one of those bore gages off thEbay yesterday, Mitutoyo 545 series. I will probably still need to get the proper anvil for it, but for $50 for a $500 bore gage another $50 in anvils is OK. It's just the time where this part is sitting in the chuck that is annoying. Luckily, I have some work that won't require the lathe.


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## mu38&Bg#

I'll be getting back to this shortly. I ended up buying a brand new Mitutoyo 511 bore gage. Ouch! Should be here in the next day or so. The Ebay deal never showed up. The first time I never got an item from a seller.


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## Swede

I'm definitely looking forward to your progress. A good spindle seems to be one of the most difficult parts of a CNC build. The choices end up being...

1) Too massive & heavy
2) too expensive
3) underpowered
4) Cheaply-made and imprecise

Trying to fix all four of these and stay within any sort of budget is a real challenge.

Did you look at the Sherline ER industrial spindle?


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## mu38&Bg#

OK. Gage arrived today, bearing bore turned out dead nuts to the .0001" with no discernible taper. I'd have to say it was more luck than my experience, unless I can pull it off on the other end. If I start believing it was all me, I won't have any excuses for not being more productive.

One end of the housing is done. More tomorrow.





Swede, I did not look at those spindles. For the price I'm sure they are worth it. And, if the above doesn't work......


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## mu38&Bg#

The housing is nearing completion. After the first end was done I needed to turn it around and make sure things were square. I didn't want to mar the finish as well. Soft jaws are the answer. These are a set I made. By the way, I'm not going through that again, to save maybe $25. This is a faux action shot of turning the jaws, they were already cut.





And the finished jaws. These are also good for holding short parts by boring shallow to seat the part. in this case I wanted a good grip.





After putting the part in I checked it with a .0001" dial test indicator on the OD. Near the jaws there was virtually zero runout. Out where the part needed to be cut off I had .0015". A couple taps brought this to .0001 TIR. Now the real test, after breaking a cutoff tool because I didn't check square, sawing off by hand, and resetting the part in the jaws, I began turning the other end features. The through hole in the housing had been bored just over 3" deep in the first setup. Once I broke through to this bore, I put the indicator on it, to find it was .0002" TIR! Great things were looking up at this point. The rest of the machining went without a hitch but for a inserts wearing. I hit the dimension within a couple tenths for the opposite bearing bore, so the first one wasn't much of a fluke. This lathe and operator seem to know what they're doing.

The body without threads, those will be CNC milled, yeah crazy I want metric threads, and this old American iron didn't come with a metric threading set. It also still needs holes for the bearing cap in the other end.





Greg


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## Swede

Looking good! Anyone who has tried it knows that large and deep bores are very challenging to execute so as to not have at least some taper.

I like your soft jaws, good idea for a project like this. 

The Sherline ER cartridge spindle is a bargain for what you get, IMO, but it will probably not rival your finished product.

For anyone interested: http://www.sherlineipd.com/spindles.htm For less than $200, you can get both cartridge, flanged, and dovetailed spindles with an ER nose rather than a MT. I have one that I was going to use, but it was just a wee bit too light. Sherline also has instructions for bearing adjustments that would allow 10,000 RPM if needed.


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## mu38&Bg#

I stayed away from the machines while I was sick and my head cloudy. I hate to think of what might happen if I made a mistake while working with one of the machines in that condition. Today, I made the bearing spacer tube that fits between the bearings. I bought some Sandvik inserts and they are very good about specifying feeds and speeds right one the box. So unlike usual I decided I was going to check to see what gives the best finish. The stock I had happened to be 4340 annealed. The recommended surface speed was pretty high to I set up for low end at ~1500RPM, but started a bit below, maybe 1200. I set my feeds so I could easily change between about .001, .002and .004/rev. I tried a few lighter cuts without at any luck at any feed rate. The cuts were the typical draggy cut I had been seeing in most of my steel work. Heeding the recommendation, I dialed the speed up to 1500RPM and .008 DOC. As I switched through the feeds I was blown away. The chips turned blue and the finish mirror-like. Now at 1500 RPM and .004/rev, things move along pretty quick. This part was 2" long so it was not a blink of the eye, but you had to be on the ball at the end of the cut.

Greg


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## mu38&Bg#

A couple more parts today. On the left the part the motor rotor will be pressed onto. On the right the motor housing. I picked up some chatter on the ID of the thread relief, it's reflected on the shoulder in the photo. I made some last minute changes to these parts after verifying the dimensions of the stator assembly. I drew the stator from a different but similar motor and this one had larger endturns (wire). Fortunately it didn't have much impact on the overall layout. I still have to pick up a few things. Bearing preload spring, probably some bearing grease, magnets for the hall sensor trigger, some 6004 bearings to use during balancing, and some teflon.

If I get around to threading tomorrow on the mill I'll post a video.

Greg


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## steamer

hey Greg

What kind of lathe are you using?

Dave


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## mu38&Bg#

It's an old Clausing 4904 that looks like it came out of a highschool. I've been very happy with it, and the tolerances and finishes I've been seeing lately have made it a great investment. The 4900 series are similar to the 5900, but were made smaller with a 10" swing. I guess most of them did end up in training environments, this one has scars to prove it. Unfortunately, parts are scarce and expensive. I'm in need of a steady rest, and they run about 400USD, IF you can find one. That might be another project if I can't source one before the job needs to be done. Had I more space I'd buy a complete lathe for spares or backup, they aren't all that unusual.


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## steamer

Check out Tools4cheap.net

He may have something that will service your steady needs.

Dave


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## mu38&Bg#

I did look at those last week. There are some with a separate base. Making a base to fit my machine would be much easier. I will look into those before I do anything drastic. Thanks for reminding me.

Greg


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## steamer

I've got one of Jeff's steadies on my Logan ( Logan steadies are almost unobtainium....when found their ridiculus)  Jeff's steady works great....needed a little bit of minor clean up and attention but it was all small stuff you find on most far east products....burrs and cleanup. Mine has a seperate base that came with it. Your right, a base would be easy to make

You can see it here.

http://www.homemodelenginemachinist.com/index.php?topic=7692.0

Dave


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## mu38&Bg#

I'll get back on this tomorrow. The threading toolpath is ready, but I got caught up in checking tram on my mutt cnc mill and did get very far yesterday. Today, I chased down an Emco Compact 6 CNC lathe. Another project... It needs a complete control retrofit. But, this will be far better than converting a chinese lathe, which I had been putting off until I could get good ball screws at a reasonable price.


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## mu38&Bg#

I got a bit sidetracked with the new lathe. I finished the threading today. Threads were cut by helocal interpolation in my CNC mill, the same mill this spindle will be installed in when done. The two parts fit together with a very close fit. This was accomplished by milling the thread into the stainless body part first, then adjusting cutter compensation while cutting the aluminum motor holder until it fit. I had made the thread relief too small in the body so it needed touching up int he lathe. I checked the fits of the bearings in the body and the rear floating bearing got tight a little more than half way into the bore. A bit of sandpaper while spinning in the lathe loosened the fit.


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## Swede

Looking exceptional! Nice work so far.


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## mu38&Bg#

Thanks! I really should get this finished before getting too involved in another project.

This is pretty much what's going into this spindle. A few parts are not in the photo. Most notably, the bearing clamp ring is missing, hopefully my daughter didn't re-appropriate it for her "collection". It's probably on my desk somewhere, it wasn't that long ago when I saw it last.

Next is drilling and tapping the holes in the body for the clamp ring.

Greg


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## Jeremy_BP

Dang. That is going to be one hell of a spindle.


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## steamer

Frameless brushless motors are how the big boys do it.  I recently finished a 14 HP spindle for a big lathe that way.

That looks very sexy Greg....can't wait for the first use in anger!

Dave


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## mu38&Bg#

I too am getting eager to run this spindle. The way things are going, I'd be disappointed if it _wasn't_ awesome.

I spotted the screw holes for the bearing cap in the little CNC mill. Due to the limitations I have now with the spindle it was just a tiny spot. This was plenty to transfer over to the Arboga and drill. I purchased in the last couple months a Tapmatic tapping head. Thread forming taps sound like the best thing since sliced bread so I decided to give it a try. I purchased a few OSG thread forming taps of their least expensive variety. I followed Tapmatics instructions for setting up the feed depth and stop on the mill. It went off without a hitch. The best thing is no chips to clean from the holes!

Tapping video later.


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## mu38&Bg#

I've also begun assembling some of the parts onto the collet holder to begin balancing it. The balance fixture still needs to be made, but it will be simple.

This is what tapping with an automatic reversing head looks like.

[ame]http://www.youtube.com/watch?v=_CUGz0jXvWQ[/ame]


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## mu38&Bg#

I've assembled some donor inner races of the same size as the actual bearings that will be used onto the shaft. The shaft is assembled with all the rotating components prior to balancing. After balancing the orientation will be marked so it can be reassembled the same way. The balancing fixture will be a simple device. I've read it's possible to do a very fine balancing job without the aid of electronics. I guess I'll find out.





Greg


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## Jeremy_BP

That's just pretty. I mean, really. You've done an amazing job. :bow: :bow:


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## steamer

That's looking awesome Greg!  I take it your using labyrinth seals?....air purge too?

Dave


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## Swede

Thanks for posting that Tapmatic head video... I've waffled over buying one of those for years. Now I want one!  :big:

Are you satisfied that the depth of the "V" formed by the chipless tap is adequate and strong?  How does it work without creating forces high enough to break the tap? Do you have to drill an oversized tap hole?


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## mu38&Bg#

Thanks for the comments guys! I'm sorting out the balancing now.

Dave, there will be labyrinth seals, but I had not intended to pressurize it. I don't have compressed air in the shop, at all for that matter.

The form tap manufacturers suggest hole sizes based on the tolerance of the thread and thread depth percentage. Recommended hole size appears to be the same among manufacturers. The hole is larger than for a thread cutting tap. This one has a 2.5 thread lead, and they make 1.5 thread lead forms taps as well. I'm not sure exactly what makes these things tick. There doesn't seem to be much of a load during tapping. A form tap has quite a bit more cross sectional area compared to a thread cutting tap. I'm convinced the form tap is a good method for making threads. It seems that the work hardened thread would be very strong. Some of the reading I did implied it's very common in production today, especially in blind holes. It seemed like quite a few guys over at Practical machinist use them, for what that's worth.

The tapping head was kind of an impulse buy. I do some prototyping in my home shop and didn't have a tapping fixture. Rather than add another piece of gear that takes up space I thought I'd try one of these. The tapping heads are sensitive enough that you can run the tap into the tapped hole again, for instance if you didn't set the depth low enough, without damaging the thread. I bought used at a very good price, but I'm not sure I could justify new.


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## Swede

The form tap method is a kind of forging, and when you forge, you get strength. It makes sense. I need to give it a shot.

I assume you use these in softer metals... mild steel as well?


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## mu38&Bg#

Right, they work in malleable materials. OSG sells carbide form taps for materials 40HrC.

www.balax.com
http://www.osgtool.com/products.asp

Greg


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## steamer

Running without air will be fine if you can otherwise remove the heat.  The amount generated will vary approximately with the square of the speed, so final top speed will be a deciding factor.

If your building a dedicated mount for this spindle, a rugged construction of aluminum may be in order as it will pull the heat away quickly...but again that will depend on how much is generated and how big your sink is....what are you running for lubrication?

Dave


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## mu38&Bg#

This project is held up by me trying to decide what to do about balancing. Realistically it needs to be balanced to G3.5 or better. Sending it out sounds costly from what I've found on line. Doing it at home is possible with some investment in software and hardware. The question is will I use it enough to justify the expense? I might have a favor through somebody, but I don't know yet.

Greg


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## tattoomike68

You work looks great but why use 304SS for a spindle? it shrinks and grows with heat like crazy, that stainless will give you fits, that's why spindles are not made from stainless.

If you were making a mixer for bread or cookies dough that runs slow then stainless is perfect.


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## steamer

Ehhh yes and no Mike. If he keeps a handle on the temperature rise, it won't be so bad

(Change in length) Delta L = Initial length x Thermal expansion coefficient x change in temperature

The CTE for stainless is 9.6 x 10-6 or 9.6/1000000 in/in/F


Another thing in his favor is the use of a DU bearing set. For the calculation above, the length of note is only the distance from the front of the bearing to the tip of the tool.  The initial length is small...maybe 2" ? It floats behind that up the shaft.

Now the big question...whats the temperature rise?....keep that small and life is good.

Lets say its as I stated and the rise is 30F above ambient

Delta L = 9.6/1000000 x 2 x 30 = .00057"

Now that's from start up to full running condition.  I very much doubt you will see that in operation as you will take a roughing cut and then a finishing cut, and the spindle will have warmed up by then and stabilized..it will have gotten to temperature and stopped growing by the time the finish cut comes around.


Now if it gets to be a lot more than 30F or 2"...well...then you may have a problem.....always wise to cool and control the temperature of a spindle.....wait till you have to do it with a spindle that has 8" in front of the thrust bearing! and your trying to hold s micron! 

Dave

Greg,

I'll send you a balance worksheet for ISO1940....send me a pm with your email


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## tattoomike68

Steamer you make some good points but like I said there is a good reason you never run a machine that has stainless spindles. If it was the right metal we would all have stainless spindles in every tool in our shops but we dont and its for a good reason.

304SS is real bad try and surface grind it and take .0002" and it will warm up and take much more then when it cools its way undersize. its fussy stuff so a high speed spindle would need so cryogenic cooling to stay stable.

I think a 4340 crome molly alloy would be a far better choice.


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## steamer

One of the biggest problems with stainless in general is that it doesn't conduct heat worth a bean....it conducts about 1/100 the heat for a given temperature difference as compared to mild steel.

That's part of the reason it grinds so lousy....the heat has no where to go and the surface temperature skyrockets...it grows a lot then!...and you hit the high stuff right a way with the grinder....the grinder digs in and generates even more heat and the cycle continues!

That's what happens when you put a lot of nickel and chrome in steel.....

I recently did some big lathe spindles (9.25" diameter) and they were ground to 20 millionths roundness (no thats not a typo) in 440C at 52Rc....after some proper heat treating and cryo work.

Anyway, I think your going to be alright Greg, but you will probably have to manage the temperature by controlling your heating....cool that bad boy!


Dave


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## Ken I

Greg, Try ballancing it on a pair of Stanley knife blades - I do this for slotcar motors that run to 120000 rpm.

Sure its only a static ballance - but if it aint statically ballanced then it aint dynamically ballanced either.

On symetrical parts it works pretty well - it doesn't always work but its always worth a try.

Always use brand new blades and be carefull not to knock dents into them which will introduce bias.



Ken


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## Florian

Ken

I have been doing this with my miniature turbine (wheel dia. around 20 mm) but instead of Stanley blades, I used razor blades. 
I found that this does not work really good and finally balanced the wheel with a self made air-bearing: 

[ame=http://www.youtube.com/watch?v=8KOKM5OYm-8&list=UUPL_cxrAxEaBeZmpIcXRdyg&index=3&feature=plcp][/ame]

However, I have been told another way of balancing by a guy who builds rc turbines: 
He takes new ball bearings, degreases them completely and then puts the turbine shaft on these bearings. 
Then he puts the bearings on the table (supported with V-Blocks) and then uses a (selfmade) vibration motor which is hold on the bearings. 

He says that this way, the shaft (including turbine wheels) can be balanced perfectly. 


This may be the easiest way for this application? 

Cheers Florian


----------



## Ken I

Florian - I'm not going to argue - both those methods are better - blades are at best quick and dirty.

When using blades they have to be in the same plane - I set mine against a surface plate and then dead horizontal - also no lube present - clean with solvent - like I said it doesn't work out every time. On slotcar motors I get great ballance about 25% of the time, acceptable ballance 50% and not so good about 25% - those aren't necesarilly good odds. The problem is typically a dynamic one due to lack of symmetry in the windings.





My two rigs - the one in the foreground is better made with leveling screws and shows the patina of a long life - I use it frequently.
I keep them in plastic containers when not in use - they're damn dangerous lying around on the bench.

I've watched the ballancing of a JT9D (Jumbo turbine) a PITB

The blades are first selected so that opposing blades are within a certain mass ballance and no blades in each set deviate by some other value. The hubs are ballanced prior and the whole assembly is ballanced - but because of the fir tree roots you can't get the exact same result twice so there's an awful lot of going backwards and forwards to get it a best you can.

Ken


----------



## Florian

Hey Ken

I did not want to say your method is wrong! 
Shurely, the blade-method works and is good enough for certain purposes. 
When I tried this, I did put the blades on a window pane to get them into the same plane. 

I suppose the problem when I tried could have been that the turbine shaft is made from stainless steel and though I tried to get a good surface, there may be some grooves left from machining... 

On the other Side the shaft of such an electric Motor is hardened and polished to get a good bearing surface. 

Well, finally I managed to balance my wheel and thats what counts... 8)

Cheers Florian


----------



## mu38&Bg#

I had the stainless. I am aware of it's properties which is why I had the material on hand for another project. If the bearing housing sucks, then it sucks, and I make another. I spent quite a bit of time reading up on dynamic balancing. I occasionally have the need to balance an electric motor for RC or maybe an electric ducted fan unit, and I do have two KP31 compressor wheels waiting for me when I decide to build a turbine. So, I might go for an all out dual plane balancing rig. I've been churning it over in my head. One additional problem is the nut needs to be balanced. Balanced ER nuts are expensive. I made a model in SW to sort out how much material needs to be removed and where, but it still needs to be checked. To get the performance I think it will be capable of, I'd like to dynamically balance it.

Yes, static balance can be acceptable. I just don't want to install the bearings only to find it's not balanced well enough then have to take it apart. Maybe I'm too worried about the bearings.

I now have a compressed air, or I have a 500W chiller available. 

Ken, I visited a friend last night with a slot car track at his house. He's been into slot cars since the 60's. I didn't know much about slot cars other than a little bit about motors. Some of the chassis were pretty wild, wire EDM steel plate, etc. for some open euro class.

Greg


----------



## Ken I

Florian  said:
			
		

> I did not want to say your method is wrong!
> 
> Cheers Florian



I dind't think you did. As my reply states - your method is better.

No offence taken either way - thanks for the post.


Greg,
    This has been an interesting post keep it up.

Some open class slotcar stuff can get really silly with rpm's and speeds people generally don't believe unless they see it. I've been doing it since 1966 although most local stuff is in the "tame" (read less expensive) categories.

Regards,
      Ken


----------



## ninefinger

Check out these links for building your own high speed balancing tool (the 1st link leads to the 2nd)

http://www.technologie-entwicklung.de/Gasturbines/Balancing_Tool/body_balancing_tool.html
http://www.technologie-entwicklung.de/Gasturbines/Balancing_Tool/Available_Parts/available_parts.html

But this is going down the road of building a tool to build a tool to build a ...

Mike


----------



## mu38&Bg#

Well, I decided to try the software. The author offers an eval copy. I think it will come in handy for other projects and balancing RC hobby motors among other things. The price is reasonable to purchase if you have a need to achieve the kind of balance levels this offers. The method he recommends requires making a temporary bearing housing as I won't be able to reach the areas needed to add or remove balancing material. I need to get a couple sensors in and then progress will continue.

Greg


----------



## mu38&Bg#

Slowly, I move forward. I've made a temporary aluminum housing in which I'll be balancing the assembly. The accelerometers arrived and I played with the software yesterday. It does indeed work very well and is very sensitive. I could have made a balancing cradle for the shaft, but I had a piece of aluminum tube approximately the right size. I still have to make the cap that holds everything to the collet holder. I'm heading into the shop and should have some more photos later.


----------



## mu38&Bg#

I didn't get very far the other night. I'd begin the assembly for balancing tonight, but I'm going to play with slotcars.





I machined a groove in the back of the cone to hold balancing putty.





I machined the cone on the shaft the first time around, but in the 5C chuck with a cheap collet. I decided it could be better and put it in soft jaws. I skimmed the outside of the cone and added the groove on the back side.





This is the cap the clamps everything to the shaft. Turned aluminum with milled cups for hall sensor magnets. I might not need the magnets if the RC controllers works, but it will be there.





The parts before assembly.

Greg


----------



## mu38&Bg#

I got all the parts together in the temporary housing for balancing. I'm ecstatic! I ran it with it's motor and it's smooth as silk! This whole project will be worth it just for the reduction in noise.


----------



## steamer

th_wwp


----------



## mu38&Bg#

Yes, pictures will come. I'll take photos (maybe some video) during balancing, and then final assembly.


----------



## Florian

dieselpilot  said:
			
		

> (maybe some video)


I hope its not only Maybe ! I WANT to see it running / being balanced ;D 8)

Cheers Florian


----------



## mu38&Bg#

I'm still working on balancing so there will be some video. The lower end is very close to balanced, the motor end needs more work.


----------



## Florian

But it sounds like its working well?


----------



## Ken I

Greg - I'm hoping you will do a post on the entire ballancing act - I'm very interested in how you did it etc. etc.

Ken


----------



## mu38&Bg#

I'm in the middle of it right now. Between the balancing, taking video, and working on customer drawings it's going a little slow, but so far very promising in the balance that can be achieved.


----------



## mu38&Bg#

OK. The balancing is about as good as it's going to get, and much better than I thought I could achieve. I do have a bunch video clips, but I'm unsure if I'll be able to put them together in a way that makes sense. I made some mistakes early on and I'd have to edit that out. Right now, I'm, reassembling the components into the bearing housing. I'll touch up the balance on the motor end if needed afterwards. I won't be able to conveniently add or remove mass at the collet end once assembled.

Cutting won't happen until after I get a mount made for it.

Greg


----------



## mu38&Bg#

This is it! I have photos and details, but that might be later. I'm spent. The collet nut will be balanced as well.


----------



## steamer

That looks great!

 :bow:


Dave


----------



## mu38&Bg#

Text is here. I haven't even looked at the balancing videos.


----------



## Swede

Beautiful!! Did I miss it, what is the power output of this gem?  :bow:


----------



## steamer

Excellent choice for Grease!....

Dave


----------



## mu38&Bg#

The motor should be good for ~1kW in this application if I can keep it cool. I hadn't planned on putting more than 500W into it though. I did a lot of homework on this project: bearings, grease, balancing, spindle design. I think I should have put more thought into the cooling and method to achieve balance. Balancing turned out OK, and I think the cooling will be OK as well.


----------



## steamer

Hey Greg,

The motor will probably be the largest heat source on that spindle.

Having said that, I would make up a cooling jacket that fits over the OD of the motor.

You might have some luck with the liquid cooled micro processors chillers for workstations....

If you have some idea of the efficiency of the motor, you can estimate the heat dumped and size accordingly

I would need to know how your mounting the spindle to advise....

Dave


----------



## steamer

A very non exhaustive search turned up this.....CHEAP hardware

http://www.koolance.com/water-cooling/new_products.php


Dave


----------



## mu38&Bg#

Dave, I haven't checked the idle current draw of the spindle yet. I've looked at PC cooling hardware for something else, but it didn't come to mind for the spindle. I have a chiller unit that I think is rated at 500W maximum. The motor heat loss is easy and I can find the bearing heat load. I'll definitely consider the radiator though. I doubt I'll need active cooling.

If you've ever seen a Precise spindle mount that's the plan. I think I'll have to order a block of material. I 

Another note, I picked up a balanced Rego Fix ER16 collet nut and wrench locally. The same guy has some connections and might be able to get me the TOS chuck I want for the Emco lathe.


----------



## steamer

Lot's depends on what the numbers are. The mount is as I imangined it would be. Should be plenty ridgid enough.

A simple expedient of a large heat sink and a fan might do it.  

The key to keeping the change in temperature down to a minimum, is to keep the flow rate of the heat transfer fluid high.
Whether it's water, glycol, or air.  Water and Glycol have very large heat capacity, so they can do this more effectively for a given heat transfer coefficient and heat transfer area....but it's not the only way, and an air cooled system sure is simple.

Keep us informed.

Dave


----------



## Simon0362

Greg,
I have built a similar spindle (doesn't look so nice though!) with a totally enclosed motor to which I have added a copper water jacket, a small pump (ex windscreen washer) and I circulate my water based cutting fluid through it. Advantage is that there is a large reservoir which substitutes for any radiators and that the fluid 'wets' onto the outside of the motor body. 

During my setup tests, I was unsure whether the cooling was going to be necessary so I had a digital thermometer probe attached to the body with a blob of heat transfer paste to ensure the reading was reasonably accurate. My 500W motor rose from 18°C (65°F) to 45°C (113°F) in the space of around 8 minutes. 
The documentation that came with my motor and casual searching on the web suggests that the rare earth magnets that these motors use should not be allowed to exceed 100°C (212°F) hence the swift construction of the water jacket. I have run it for about 30 minutes non stop and the temperature now rises by no more than 2-3°C, so a worthwhile exercise.

Simon


----------



## mu38&Bg#

Thank you, Simon, for the information. This motor has high temperature magnets, probably 150°C. I know one guy that builds spindles like this ran his coolant through the spindle motor and then on the parts, and then back to the tank. I don't remember exactly how he was filtering it, but he was happy. A large reservoir is simpler and more reliable than a radiator and fan.

The reason I considered using compressed air through the motor was because of an experience I had with a brushed motor in an RC model years ago. I set it up such the the cooling air flowed through, not around the motor like most designs. The result was very obvious in reduced heating and consistent power through the flight. It doesn't take much air when you can get directly to the parts that need it. Of course in this case I'll probably do the math before trying it.

Greg


----------



## Swede

Greg, I think the simple act of mounting that beauty in a nice fitting block of decent mass will take care of 90% of any heat issues. I have a KaVo spindle of very similar profile that I mounted in a big aluminum block mount that was precision-bored to take the OD of the spindle. The block in turn dumps any heat into its own mount.

Even at high/long sustained effort, the setup barely feels warm. I'd try it first without anything exotic. Plain old heat transmission through metal will hopefully do the trick.

My system does take filtered, compresses air internally which certainly helps cool, and also creates positive pressure internally to protect the bearings.

The commercial variants of this spindle type are unbelievably smooth running. Again with my KaVo at 50K RPM, there is barely any noticeable vibration. It looks like you have replicated a complex and expensive spindle at home. A superior job and beautiful results.


----------



## mu38&Bg#

Thank you for all the input. I'll mount it, see what temperatures look like, and make a decision on the cooling. The block of aluminum for the mount arrived today. I hope to get started tonight.

Greg


----------



## steamer

Depending on how much heat your dumping Greg, as Swede says, a big block and a good fan maybe all you need!

Have you cornered how much heat you have to dump?

Dave


----------



## mu38&Bg#

No, not yet. I've been busy with other things. The only thing left is the mount. So it won't be long.

Greg


----------



## mu38&Bg#

The mount is turning out to be a lot of work, which I somewhat expected.





I started with a block of 7075-T6 about 4.25"x5.5"x2.6" and hogged most of it in the Arboga.





On the left, before CNC, on the right after. The second side is still running in the mill. It's a 2 1/2 hour program mostly due to the feed limitations I have right now. After that will come cutting the hole for the clamp screws, boring the hole for the spindle, and finally splitting it with a saw in the mill. I never paint my tools, but this might get a coat of something. I'd anodize it if I was set up for it. There is one booboo from thinking about Paczki on Fat Tuesday when I should have been thinking about which way to crank the mill handles.

Greg


----------



## Swede

Are you going to split it so that when the clamp screws are tightened, you'll get good surface contact? If so, I'd guess this will be more than adequate for cooling.

Nice work.


----------



## mu38&Bg#

Yes, it will be split. Right now, I a little stuck. I have a faceplate for the lathe that feels a little too small for this. I think I can do it safely if I make a plate to clamp the mount to it, but I'm only going to be able to use three bolts. Then machine right through that plate. The four jaw chuck I have would hold it but I don't feel comfortable using it. I suppose if I kept the cuts light it would be safe. I do have a large four jaw that's been waiting for a new backplate to fit the Clausing, but I don't have a spare backplate to machine. Because I don't do any coarse internal threading, I don't have an internal threading tool even though I do have a chunk of suitable cast iron allotted to another project.

Ooops, I typed that yesterday and it's still here on my screen.

Anyhow here are a few more pictures. The chunk of cast iron was spotted elsewhere in the shop after I started cutting the backplate. It must be a piece I got in a toolbox I bought. Steel of some sort, actually pretty tough stuff to drill and tap, but turning was awesome. The backplate turned out fine and I mounted the large four jaw I had. Boring is not done yet. Slow going due to low speed, unbalance, and somewhat scary setup.


----------



## steamer

Looking good Greg!  Just go slow and peck away...you'll get there.

Are you going to relieve the center of the flat foot?

Dave


----------



## mu38&Bg#

Hmmm... I didn't know that I should? To prevent heat transfer to the axis? To make it more stable? I don't think I've ever seen that before.


----------



## mu38&Bg#

I'm within a few passes of being done, but I'm calling it a night. Maybe I'll do the first cuts with the spindle tomorrow!

Greg


----------



## steamer

No just to make it easier to align later.....then again you probably have a better mill than me! : ;D


----------



## mu38&Bg#

Well, the setup I have now doesn't use anything to align it. Once installed/trammed it doesn't get moved so I don't use any pins or adjuster screws, etc. My mill is probably not what you think.....


----------



## Brass_Machine

dieselpilot  said:
			
		

> Well, the setup I have now doesn't use anything to align it. Once installed/trammed it doesn't get moved so I don't use any pins or adjuster screws, etc. My mill is probably not what you think.....



I hadn't seen your mill before... I knew it was DIY, but I didn't know it had a concrete column. How does it perform?

Eric


----------



## mu38&Bg#

It's OK. My current spindle is a problem so I'll know the weaknesses when the new one gets going. The bottom plate likely needs reinforcement.

I didn't have a cutter to slot the mount with so it will be tomorrow evening.


----------



## mu38&Bg#

The spindle mount is done. The spindle is balanced. I ended up removing a lot of weight I added. I did something wrong along the way. Now, I just need to put it all together. I'll have photos and video later. EMC2 is talking to the RC speed control, but scaling is incorrect, it will work for now.

Greg


----------



## mu38&Bg#

This is a picture of the mounted spindle. I did rebalance before putting it in the mount. I ended up removing some weight I added. I figured out what I did wrong, but didn't redo the nose end of the spindle so I think this is the problem. I also have doubts about the supposedly balanced collet nut I bought. I did run the spindle mounted to the mill, but there was some vibration I wanted to check out. So it's off again. Then I spent a couple days cleaning the shop getting ready to move everything to make room for the next project, the Emco lathe retrofit. Hopefully I'll get this balance issue sorted tonight and I can make some chips on video. tomorrow.

Initially, the no load currents were very high, like 20A at 22V input. They quickly dropped to under 4A at 22V. This is about 15kRPM. I checked the old spindle I was using and that was about as fast as I ever ran it, so the 30k idea might be way over the top. There is 90W of heat without load at 22V. The bearing housing and mount appear to stay fairly cool, the motor gets hot after a few minutes. I think I'll have to order some material to make a water cooling sleeve. I think the bearings are also over the top for the cutter sizes anticipated. I see some things I would have desinged differently, namely providing better access to the nose end of the spindle for balancing.

Greg


----------



## steamer

Is most of the 90 watts at the motor?....You may be able to sink that and use a fan...

Looks Great!



Dave


----------



## mu38&Bg#

WooHoo!! I finished the rebalance and checked the collet nut. The collet nut I bought that was to be balanced wasn't! Oh well it's still a nice bearing nut I'll use with the Arboga. Instead I balanced the original nut that came with the collet holder and it turned out reasonable.

This is the first part!





And, some video as promised.

[ame]http://www.youtube.com/watch?v=fGrITuuTZtQ[/ame]

Dave, yes most of the heat is the motor. I ran this part without cooling and it ran for 30 minutes. It was OK. I don't know if the change in temperature of the aluminum mount and block is worth worrying about. I thought about running the coolant through the mount. I'd rather use a fan if I could.

Greg


----------



## steamer

Hey Greg!

Awesome! Looks and sounds great! Congratulations...now you know why those spindles cost so much! ;D

You did a great job!

As far as the heat, always take the heat out where it's generated first ...if possilble
I would first try a heatsink and fan on the motor casing, keeping the temperature distribution as symetric as possible....ie even all around and along the length.....this is technically impossible, but strive for it.  A coaxially mounted computer fan blowing along the length of the motor will give a symetric air flow around the motor and should be simple to do. You will need some air flow though!

If you can dump 90 watts with a heat sink and a fan over a relatively small temperature differenc, you will have a very simple system without all the grief of a fluid system...trust me on this you will be better off if this works out.

If it doesn't work out, and you go with a liquid coolant...the same rules apply.  Flow rate is your friend, as it allows you to remove heat across a smaller temperture difference.

Congratulations Greg!  Ya done good!,,,nice machine....I would like to know more about your composite base. I'm used to granite and epoxy/granite, fee free to start a thread on that if you like.

 :bow:

Dave


----------



## mu38&Bg#

Dave, Thank you. I'm very happy with it. If I bought the bearings at retail it would have been 400-500USD, in bearings alone. I already had the motor or that would have been another 290USD, although I could probably use something smaller. I am going to try a heat sink and fan.

The base of my mill is a piece of quart countertop material. I'd have to check, but it's about 1.25" thick. Initially the idea was to use a 18x24x3" granite surface plate I purchased cheap. But to fit what I thought would be enough column it came up just a bit short. I think this is the weak point in my machine right now. I've been thinking for a long time to epoxy some steel angle or channel to the bottom to improved rigidity. This machine was built in 2004, before I even had my first lathe. The idea came from reading Swede's 5bears.com site when he built his. I didn't have access to any metalworking equipment and I was being cheap, so that was what I came up with. The linear slides are Aerotech Accudex units. 12" X and Y and 6" Z, and they do very well. The resolution of the axes is 2 micron by the encoder, and if i remember from the specs this is also the repeatability for the ones I have. The Z axis is too light really, and I might build one if I can't find something I like on Ebay. I do have a large 24" slide of some kind I bought for a different project a long time ago, and I'd love to make X travel 24", but that entails a lot of down time unless a build a whole new machine frame and transfer parts. Anyhow, the next step is to finish a 4th axis I started just before the spindle and build some projects that have been waiting for that.

Greg


----------



## petertha

Your spindle construction is such a cool project. I know virtually zip about CNC or spindles or their running environment, but I DO recognize the round black thing in the end & practically consider myself an expert in the many ways to cook them! (F5D racing) ;D

Somebody smarter than me could do a heat calculation, but my gut sense is if you are running 30 minutes with moderate temp buildup now, you could probably cool it with some combination of heat sink type fins + DCV cooling fan(s) lik in PC's. Ive seen RC heli & car world installations like attached pics, where their motors are also confined to dead air. Maybe a scale-up & better orientation?

In/out water jackets like these are quite common for RC boaters. 
http://www.offshoreelectrics.com/products.php?cat=Motor+Water+Cooling

The jacket & basic plumbing would be easy with your machining skills, but replacing the lake with pump & exchanger hardware like PC liquid coolers looks a bit more complicated. Im not sure what heat wattage values they handle, but they have the ingredients to modulate it closely if thats an issue. 
http://www.koolance.com/technical/howtobuild/index_01.html


----------



## mu38&Bg#

Hey Peter! I've been playing with electric airplanes since 1997 or so. Flew F5D 1999-2001 or so. I went to the F5 worlds in San Diego as a mechanic for the F5D team. I used to work for MPI who sells Himax motors. Been bust with other stuff. I still need to look at the figures. I saw only 8-9A while cutting under load so the motor is still only 50% efficient at best. Regardless the heat load is fairly low. It's possible that I'll make a new motor housing incorporating the cooling fins. Right now I'm doubting I'll run 30kRPM, so I might change the stator out for a lower KV and run higher voltage. For water one of the 56mm jackets would work. Thanks for the link. That would be the easy solution now as I have a chiller on hand.


----------



## steamer

That Traxxas block looks familiar greg!....except mine was 16" in diameter! :big:

Can't beat the price!

Dave


----------



## mu38&Bg#

I ordered a 56mm water jacket. I'll see how that does when it comes in. I've made a few parts and it looks like the crossed roller bearings in my Z axis needs to be tightened. The spindle looks good.


----------



## mu38&Bg#

The water jacket arrived. I installed it and connected it to the chiller I have. I didn't make the jacket because I thought for such a simple part, how bad can it be to buy some Chinese import? I had to reinstall one hose fitting and one of the O rings barely holds water. : The chiller certainly does it's job and there is far more capacity for cooling than needed. I don't feel like making a heat sink for air cooling right now, so the machine will run like this until that time comes. I still have to find my high voltage RC motor controllers to try the 48V I intended. While I didn't think I would need it things have been running very well.

Today, trying some new feeds and speeds, I set it for 4mm deep cuts and 10% stepover at 1000mm/min with a 1/4" 3 flute at ~15kRPM in 6061 aluminum. This was running pretty well when, all of a sudden, it does a full width pass! I know that Visualmill does this to me every once in a while but didn't check this part. I was reaching for the Estop when it plowed right through without slowing. I'm still running the spindle on my bench supply and watched as the current jumped to 23A(~500W) on the other side of the part in another full depth pass. I have to say I was mighty surprised when things didn't go awry. The rigidity of the spindle and large bearings really pays off. My mill seems to be doing well also, just the Z axis may need to be tightened or replaced with something a bit more sturdy.

One thing for sure is you want good collets at these speeds and feeds. I did some parts with a .070" endmill which I used a nice Lyndex ER16 collet for and that really ran well.

Greg


----------



## HS93

Have you seen these they will take 50v , I have had a few for boats for a few years and they are one of the only speed controllers that have a repair service, and for you American made


http://www.castlecreations.com/products/phoenix-ice2-hv.html

Peter


----------



## steamer

Congrats Greg!  Well Done!

Glad she's more capable than you originally suspected!


Dave


----------



## mu38&Bg#

Yes, I'm a fan of Castle creations. I bought controllers from Patrick when he was making them in his basement and sold them when I was in the business. I do have a PH-45HV ....somewhere. I'm checking Ebay for a suitable industrial control that will integrate with the control a bit better.

Greg


----------



## petertha

dieselpilot  said:
			
		

> ...4mm deep cuts and 10% stepover at 1000mm/min with a 1/4" 3 flute at ~15kRPM in 6061 aluminum. .. all of a sudden, it does a full width pass! Greg



Youch! One thing your awesome build thread made me realize is how little I know about spindles. I have come to appreciate they are not just a shaft running in some bearings! 

When you sized your spindle bearings & internals, how do you determine the max side load it sees in typical/max depth cuts to begin with? Not sure if 'side load' is proper terminolgy, but I mean the force that the shaft/bearing see in the x-y plane of a cutter vs the downward plunge force in the z-axis?

Reason: my understanding of spindles in specialized grinders (toolpost or tool cutter style) similarly require tight tolerances at high rpm, and obviously some force. How does one get a handle on this infomation? I also noticed a few spindle variations on Quorn-type tools where the motor is remotely driving. I ordered this book for some basics. 

http://www.amazon.com/dp/1854861492/?tag=skimlinks_replacement-20


----------



## mu38&Bg#

I still don't know that much about spindles. I did learn that I could make a better one now. There is a lot of information in the machine bearing catalog in the Timkem lineup. Check all of the manufacturers machine tool bearing catalogs for references. Cutting tool power can also be calculated. This one from Mapal is good.

As long as the motor can keep up, things will be fine. My DC bench supply is a 2.5kW 46A unit. Had I set the current limit less than 25A or used a lesser power supply the results would have been very different.

I did break a 1/4" end mill yesterday. I tried finishing the part with 4mm deep passes, but it got too hot and clogged the cutter. The endmill has a lot of use, so it was probably dull too. I learned when I had my old spindle to do shallow passes at large step over while roughing to avoid overloading the spindle if the CAM threw a random full width pass in there. After the tool broke I went back to .75mm, 75% step over and finished the part. The run time was essentially the same and I could have skipped one operation that I felt was needed when I was using the deeper passes. So, it would have been about 10% faster. I might look at G-Wizard to assist with feeds and speeds.

Greg


----------



## mu38&Bg#

It was a bad day yesterday. I scrapped a small part milling a thread. Then trying to figure out why center wasn't on center, I crashed a thread mill. I was fairly upset about the 60USD tool I wrecked and the delay it was going to cause on a paying job until I can get one in. I ran a different part on the mill and noticed the finish wasn't quite right. You guessed it, the spindle now has a runout of .001". Boy was I furious. I do have another collet extension like the one I used and will rebuild it. Hopefully, the cone on the shaft comes off and I don't have to make a new one. If I had the means I'd regrind the ER taper, but it would still be bent. I guess the collet extensions are fairly weak. I'll probably never use a 3/8" endmill in this spindle but crashing one would be sure death for the spindle.

If I was doing it again I'd design for less overhang past the bearings. I was a little worried about it, but am still surprised it bent. I might even use a larger diameter shaft at 25mm and the next lighter bearing will have the same 42mm OD. But, if I was going to build an entirely new spindle, it would have an automatic tool release to allow for quick change tools and the tool length offsets. That probably won't happen anytime soon.

Greg


----------



## petertha

Ouch. Sorry to hear that Greg. Problems are never welcome. But they seem to have an uncanny habit of showing up uninvited particularly when least convenient. I think we can all relate. Well, I know whatever you come up with will be better yet!


----------



## Florian

Hey Greg

Thats a Pity! 

But: 
Why dont you make your own spindle, get it hardened (that's not expensive) and finally have it ground to size? 

Of course its more expensive than getting a new straight shaft but with all the time you have spent, i would say it is worth it. Maybe someone here on this Forum could grind it for you for a better price than if its made by a company (which has to pay employees and all the other stuff...) 

Cheers Florian


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## mu38&Bg#

After disassembling the spindle, I now have more trouble. The shaft that's been damaged the has very little runout on Vee blocks. This is somewhat expects because I don't have the Vee blocks where I had bearing mounted. The second new shaft I have actually shows greater runout on Vee blocks. On top of that, the balls in the duplex bearing pair show bands. I don't know what this is caused by and am trying to find some information.

What I'm going to do is put this back together with the new shaft and give up. If the time comes for a better spindle, I'll look at this again.

This just shows that a simple programming error can destroy a CNC machine instantly.

Greg


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## steamer

Sorry to hear about that bud!  I hope you didn't wipe the bearings out....are they smooth?

Dave


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## mu38&Bg#

They feel smooth, but spinning it I can ever so slightly hear a high pitch buzz. I do have more bearings and at the twenty some odd dollars a pair I found them for, it doesn't hurt, but I don't want to burn up another set. I'll continue to run this set until problems become serious. The only reference I found to ball banding was reverse loading of angular contact bearings. These are definitely installed correctly. if I knew how to get these apart I'd have a look at the races.


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## Florian

Hey Greg

What do those "bands" look like? Maybe there are induced currents going through the bearings?? (This would harm bearings and make "bands" on the races. 

Maybe you can cut one of the bearings races if they are crap and see what the raceway looks like...? 

I mean, what may has happened is This. 

Cheers Florian 
btw: If those shafts are all crap; just make your own and use it unhardened! If you use some high-tensile steel, the collet cone will last quite long. Then you could also make it shorter so the bearing is as near to the collet as possible...


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## mu38&Bg#

I don't think it's current. The upper bearing looks like new. The bands are just hazy. They don't catch on an Exacto blade. It's quite possible it's just the very early stages of wear due to the crash. I think the spindle squealed for a second the first time I started it afterwards. It ran for three minutes or so.

These bearings have one piece composite retainers. I'll have to figure out how to get them apart to look at the races. I'm thinking they'll just fall apart if I give the inner race a push.

I don't have the means to grind the spindle or I'd think about making one. Quite honestly I just don't have the time to work a new spindle unless the replacement shaft turns out to be unusable. I have a project planned that needs a .050" endmill with a .5" reach. It won't handle much runout.

If anyone is planning a similar project, I'd stick with 1/8" tooling.


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## Florian

Hey Greg

With the new Shaft, if it is not running true and you own a dremel, you could try this: 

Clamp your Spindle in the 3-Jaw Chuck of your lathe.
Support the spindle in the front with a fixed steady.
Then adjust the compound slide to the collet cone (using a dial gauge with lever). 
Now you clamp the dremel on the compound slide and set its center exactly to center height of your lathe. 
You can use a Aluminum oxide grinding stone for grinding the cone. 

You should also cover all the ways of your lathe and if possible use the shop vac when grinding. 

Finally you can run the spindle slowly, in opposite direction to the dremel and use the dremel on the compound slide to grind the collets cone. 

When grinding you should only take very light cuts and always move forward an backwards a few times until there are no more or only very few sparks when moving. 

I think this can be done in 1 to 2 hours and you will have very small runout because you have ground the cone IN the spindle while it was running by itself. 


So, if required and if you own a dremel, I would say give it a try! 

Cheers Florian


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## Mosey

My old old Dremel is loose in it's bearings. I have a cross-slide mount that I made, but I assume that since it is wobbly, I shouldn't try grinding on the lathe with it, right?


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## Florian

Mosey  said:
			
		

> but I assume that since it is wobbly, I shouldn't try grinding on the lathe with it, right?



No, not exactly! 
Of Course you won't get the best possible surfaces this way but the grinding stone will place itself to where there is the least forces on the (dremel) shaft. And If you work carefully, you will get quite good results with that. 

Of course you will get better surfaces with a grinding spindle but the surface you get with the dremel should be good enough for the collets. It is also important that you set the grinding stone that it touches the cone only on a small area and not on the full lentgh. 

Id say try what happens. 

By the way if the surface of the cone is not as good as you want it to be, you can make some aluminum arbors with the collets shape and then lap the cone with some diamond paste. 

Cheers Florian


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## mu38&Bg#

I just got the new shaft into the spindle. The bearings don't make the whirring noise so maybe there will still be some life in them.

However! Taper runout is worse than the bent spindle, almost .002" TIR. That first collet extension must have been a fluke at virtually perfect.

I was hoping not to rework the taper, but it seems I have no choice now. I really doubt the Dremel. I used a much more stout grinding spindle, though with a little runout on the taper, on the lathe and I wouldn't use it for this. I might mount the spindle in the mill with a boring bar on the table and write a program to true it.

Greg


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## steamer

Either that or mount the assembled spindle housing into a steady rest and turn it.   If it's not that hard.

Otherwise....the mill approach is a decent one......I think.

Dave


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## Florian

steamer  said:
			
		

> the mill approach is a decent one......I think.



I thought about this when i wrote my last post but left it away because i excepted the z-clearance to be too small for doing this... 

But if you can manage to, this would be the best way I think. 

Cheers Florian


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## mu38&Bg#

Well, it's back together. I had a heck of time balancing it again. I gave up and only got it close, but it runs smooth installed in the mill. I mounted a carbide tipped boring bar in the vise and wrote a program to true the taper. It turned out about .0002"TIR. A rod in a cheap collet was about .0006" TIR. I'll live with it for now, a good collet should do better anyhow.

Note to self, on the next (yes, I'll punish myself) spindle design balancing into the components with easy access.

Greg


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## steamer

Hi Greg,

The design of spindles is really tough. There are so many conflicting trade offs.
I think you did great!
 :bow:
Dave


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## steamer

....and they're ALL hard to build!   Now you know why they cost so much!
 :big:
Dave


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## mu38&Bg#

Yes of course, you're right. It does work well. it just isn't strong enough for mistakes. I forgot to check the alignment of the Z axis after the wreck, and ended up fixing that yesterday. I just have to be very careful about not crashing this until I can decide about a studier machine.

Greg


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