# Boring head Ball/Radius turner



## rodw (Apr 27, 2014)

There seems to be heaps of threads on ball turners on the forum but not much said about using a boring head to do this. So here is one set up to fit on a BXA tool post.






















When I bought my boring head, I bought an additional straight shank mounting flange for it. It had a 20mm diameter shaft. I bought a pair of 42mm x 20mm x 12mm bearings which only cost $5.50 each. The body is made of aluminium (from 50mm x 100mm flat bar) and the handle is 12mm steel. I found some plans online but I had to redo them as they were for a CXA tool post. 

I improvised with the height adjustment  over the weekend for now and used a washer sandwiched between two nuts and I was able to centre it OK. You only need to do this once and is pretty easy. It is just a matter of adjusting the height until the tool touches the top and bottom of a piece of round stock in the chuck.

So drill and tap the end of some bar stock, part off the piece so it is the same length as the diameter and go for it!






Just wind the tool in gently and take your time with small cuts.

















Umm... loosen the ball before you polish it as it was very hard to get a grip to unthread it from the mandrel (just use any old bolt the right thread)






Beautiful!

To polish it, with the lathe running at 500 rpm, I started with 240 grit sandpaper  and moved up to 400 wet and dry kept wet with some kerosene. Then moved up to 600, 800 and 1000 grit (with kero) before the final polish with Autosol metal polish which you should be able to get from a car accessory store. Looks like chrome!






Oh and another tip I learnt somewhere, maybe even on this forum. When tapping a thread in a lathe or mill, remove the anvil from a self punching centre punch and use it to hold the tap centred. 





this really works  treat and the tool can be returned to normal (but as I had 2, I cut a ring around one with the lathe) so I know which one is what.


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## chucketn (Apr 27, 2014)

I was so impressed with this post, I spent the day making the parts to make my version of your ball/radius turner. I have made a tool holder for my OXA QCTP, and a straight shank adapter for my 2" boring head.
May I be so bold as to ask for a video of yours in action?
Thanks for an inspirational post!

Chuck


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## rodw (Apr 29, 2014)

chucketn said:


> I was so impressed with this post, I spent the day making the parts to make my version of your ball/radius turner. I have made a tool holder for my OXA QCTP, and a straight shank adapter for my 2" boring head.
> May I be so bold as to ask for a video of yours in action?
> Thanks for an inspirational post!
> 
> Chuck



Chuck,

I am humbled by your blind adoption of my idea...I am glad you liked it! Just one thing that you might like to consider. If you look at the pictures you will see I drilled a hole in the shank adapter to me it easy to undo the boring head as I can insert an allen key in the hole to undo it! It was easy with the adapter held in a collet in a collet block!

I have looked at various threads on ball turners and thought they were an enormous amount of work but when I saw this design, I was really impressed how simple it was but it still took a day and a half (and the rest of the second day to make and polish the first ball!)

It is a bit of a pain to set up my DSLR to shoot video in my shed but I put my little old SD video camera on the charger tonight but won't make any promises.


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## chucketn (Apr 29, 2014)

I wouldn't say blind, Rob, needing glasses, maybe, LOL. Mine will not be an exact copy, but functionally the same.
I need to study up on making a bearing pocket, have 2 to make on the tool block. I'll post pictures if It comes out.
I would appreciate any kind of video, thanks for trying.

Chuck


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## Brian Rupnow (Apr 29, 2014)

Very nice design. It shouldn't need bearings though. Bushings should be more than adequate for this mechanism.----Brian


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## chucketn (Apr 29, 2014)

Brian, I intend to use the tool block as a cross drilling platform as well as for the ball turner. The shaft that holds my adapter for the boring head is threaded for 3/8" x 24 tpi, so the adapter can be swapped for a drill chuck. I havent worked out the handle end yet, but it will also be the drive end for the drill rig.

Chuck


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## Brian Rupnow (Apr 29, 2014)

chucketn said:


> Brian, I intend to use the tool block as a cross drilling platform as well as for the ball turner. The shaft that holds my adapter for the boring head is threaded for 3/8" x 24 tpi, so the adapter can be swapped for a drill chuck. I havent worked out the handle end yet, but it will also be the drive end for the drill rig.
> 
> Chuck[/QUOTE
> Chucketn--Most drills I have seen use bushings as well. It certainly won't hurt to have ball bearings there. I just don't know as they give any advantage over bushings.---Brian


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## chucketn (Apr 29, 2014)

I'm interested in all techniques, Brian. Would I need oil ports if I used bushings? I have brass rod big enough to make bushings from, I think.

Sorry to hijack, Rod.

Chuck


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## Brian Rupnow (Apr 29, 2014)

chucketn said:


> I'm interested in all techniques, Brian. Would I need oil ports if I used bushings? I have brass rod big enough to make bushings from, I think.
> 
> Sorry to hijack, Rod.
> 
> Chuck


 chuck--I would recommend oilite bronze, not brass. I know we all use brass in our model engines for bushings, and they are really not subjected to heavy loading, so they work all right. To build an arbor or tool head with a revolving shaft, ,bronze is the most wear resistant material. Oilite bronze bushings are best, because they are porous and filled with lubricating oil. They don't really need an oil port, although again, an oil port won't be detrimental to them.


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## chucketn (Apr 29, 2014)

Do US hardware stores still carry oilite bushes in the specialty hardware area?

Chuck


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## MachineTom (Apr 29, 2014)

The ACE hardware I deal with has a small selection, MSC and the others have lots. For something used like this would be, slow, infrequent, I'd put a dab of grease on the bushings, and suggest the grandkids can do it again in 20 years.


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## Brian Rupnow (Apr 29, 2014)

No, but any of the industrial bearing supply houses carry them in just about any size you can dream up. You can also order them on-line. I have an old Boston Gear catalogue here that lists a bunch of different sizes. Do a web search--just be sure to specify Oilite bronze. Don't buy 660 bronze, because it doesn't have the self lubricating properties.
http://www.isostatic.com/index.html
http://www.symmco.com/


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## rodw (Apr 29, 2014)

I thought about making a bush from bronze and the body from steel but my supplier  would have had to get the bronze in when the ally merchant and bearing suppliers are almost on my doorstep. The cost was also lower! 

I thought seating bearings and getting them aligned would be a good learning experience and an excuse to use my coaxial dial indicator to line up the second side. I drilled through to 22mm and bored out to 28mm just for fun! I cut the pockets the depth of the bearings. The first one, I made a bit too loose but I snuck up on the tolerance the second time round and it was a hammer fit. The loose one, I glued in with some locktite 609. I clamped it and left it overnight and all was good in the morning.

As far as the handle went, that was easy, I put a washer at the front so the flange had clearance against the bearing outer race. The shaft then sat in about 3mm from being flush with the bearing on the back side. The shaft had a 10mm thread for a drawbar.   

I machined up the handle hub with a through hole and a step in the mating surface on the bearing side. The first  2mm is the same diameter as the shaft to locate the handle snug and the next 1mm was the same size as the bearing inner race for clearance again so it did not bind. I just bolted the hub to the shaft and it is tight enough not to move and this also removed any lateral play in the bearings. I found I needed to take light cuts so there is not that much pressure on the handle. 

Given you are making your spindle, maybe you can slot the end of the shaft and add a tongue on the handle end so you get positive drive. You could then bolt on a smaller hub you could put in your drill chuck when drilling.

The handle I decided to angle out 10 degrees for fun but this was not necessary. I bolted the hub to a piece of threaded round stock and held it in a 5C collet block in the milling vice with an angle block to set the angle. I also used this fixture in the lathe to polish the hub before drilling and tapping for the handle.

I will be interested to see how yours turns out and how you incorporate the drilling fixture. I don't think I need this as I can drill holes on the mill.  I think it would be easy to make up a sleeve that pushes through the bearing to use as a drilling guide rather than add the chuck. 

Some people make up  a boring bar with a reversed insert cutter but the cheap brazed tipped bar I used works OK even if you do cut in the reverse direction.

 Hope the extra info helps.


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## chucketn (Apr 29, 2014)

Thanks for the input, Rod. I had to make a couple of design changes today, as the assembled length with the boring head and adapter is too long.  May have to take a bit off the tool block also. It will still be useable, though. 

Chuck


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## rodw (Apr 30, 2014)

chucketn said:


> Thanks for the input, Rod. I had to make a couple of design changes today, as the assembled length with the boring head and adapter is too long.  May have to take a bit off the tool block also. It will still be useable, though.
> 
> Chuck



Good to hear you are making progress. If you look carefully, mine is not symetrical to gain as much room as I could get by moving the head backwards.

Here is a video for you.

http://youtu.be/gnt2DIcrWYk


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## chucketn (Apr 30, 2014)

Very nicely done Rod! Hope I can do as well! Great video!

Chuck


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## rodw (Apr 30, 2014)

chucketn said:


> Very nicely done Rod! Hope I can do as well! Great video!
> 
> Chuck



Thanks, glad you liked the video. I think it will be the last from me for a while as I dropped my little camcorder after I took this video and it died! 

Just when i worked out a nice simple way to mount it above the lathe too!

Don't forget you owe me a couple of photos too!


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## chucketn (Apr 30, 2014)

Sorry about your camcorder, I didn't mean for you to break it! Off to the shop to work on my version...
Thanks again for the inspiration and taking the time to make a video!

Chuck


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## chucketn (Apr 30, 2014)

I modified some of my parts for my version of Rodw's ball cutter, but still no joy. Here's my parts so far. 
As you can see from the second pic, I'm still approx. 3/8" from being able to center the cutter. I'll remake the adpter, and there is room to take maybe 3/16" off the front of the tool block. Even with the compound topslide reversed and cranked to it's limit I can't reach center. And, that is wth the7x travel mod.

Chuck


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## chucketn (Apr 30, 2014)

I could also make a custom cutter from drill rod, but I think that would limit the size of ball that could be turned.
Chuck


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## Brian Rupnow (Apr 30, 2014)

The tip of your cutter is already past the center of the chuck. You don't need to reach in any farther than that .Here is a rather shabby youtube link to the cutter being used.
[ame]http://www.youtube.com/watch?v=6ygtJFBRUOU[/ame]


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## kquiggle (Apr 30, 2014)

It's a bit of an obsession with me to collect links on different types of ball turners (see below) - yours is one of the few I have seen recently with a really different approach. Thank you for sharing.

Now I'm wondering if I can get something similar to fit on my little 7x12.

https://sites.google.com/site/lagadoacademy/useful-links#lathetools


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## chucketn (Apr 30, 2014)

That's my goal, kquiggleI I have had to re-make the threaded adaptor for the boring head. i'm working on that now.
Though my lathe is a 7x14, should work for you, too!

Chuck


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## chucketn (Apr 30, 2014)

Brian, the tip of the cutter in the picture is in fact, too far past the center. I need to move it toward me at least 1/4".

Chuck


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## Omnimill (Apr 30, 2014)

This may be a problem for use on small Lathes, the body of the boring head takes up a lot of available travel.


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## Brian Rupnow (Apr 30, 2014)

Chucketn--I see. ---My bad.----Brian


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## chucketn (Apr 30, 2014)

After spending the day remaking, and remaking some parts, I have come to the conclusion that RodW's original design of the body of the ball cutter was not without purpose. His design allows setting the body of the boring head back from the lathe center line. If I have to start over, my version will follow that design. My version, in its present form, only works if I swivel the topslide around to where the crank handle is to the right and the rear of the lathe.
I have almost finished reconfiguring my version. 
I stopped when my back started aching. Tomorrow is a new day!

Chuck


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## Swifty (Apr 30, 2014)

Can't help but notice the wearing of gloves and leaning on the headstock while the chuck is rotating, as well as a loose fitting t shirt not tucked in.

Paul.


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## chucketn (Apr 30, 2014)

Omnimill said:


> This may be a problem for use on small Lathes, the body of the boring head takes up a lot of available travel.


 
That it does, but I hope to overcome it...

Chuck


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## Brian Rupnow (Apr 30, 2014)

Swifty--that isn't Chucketn. That's just a video I grabbed off youtube.---Brian


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## rodw (May 1, 2014)

Brian Rupnow said:


> The tip of your cutter is already past the center of the chuck. You don't need to reach in any farther than that



Brian, thanks for posting that video. I watched it after I had mine half done to give me an idea on how to use the darn thing! I thought it would be terrible if I got it made but could not work out how to use it!

Chuck, Brian is right, you only need to reach the centre of the work piece so you will be fine. It takes a while to get your head around the geometry but the spinning lathe means by the time you get to the centre of the piece, the back side has already been machined. You just advance the tool into the piece to take manageable cuts.

I have attached some PDF plans I did up but I ended up modifying the design without updating the plans. The plan shows the area the shaft passes through to be 76mm long but it only needed to be 50mm. I cut a T shape out of the block to achieve this and centred the dovetail on the leg of the T. From memory, I think the 19.6mm dimension became 28mm and I cut away about 21mm at the back. The 28mm step meant the head was recessed back as far as reasonable but the micrometer adjustment is always reachable.

Note the plans show a hole for a pin to limit handle travel with a stop that fitted round the hub but I don't think it is necessary and I left it off.

Hope the PDF helps for those attempting this.

kquiggle, thanks for adding my design to your collection. I will go back and look at your collection soon. 

View attachment Ball Turner Plans.pdf


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## chucketn (May 1, 2014)

Rod, the present configuration does allow me to reach center, but limits the size of ball I can turn. I didn't measure it, but I will later today.
I think 
I think I will re-make the tool post with an offset like yours to allow bigger diameters.

Chuck


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## Brian Rupnow (May 1, 2014)

RodW--I built a ball turner similar to yours today, using my boring head. It works quite well, but the brazed carbide boring tools I have leave a really ugly/nasty surface finish on the aluminum ball.  I hadn't thought too much about it before making mine, but the forces which transfer from the turning part to the boring bar actually reverse when you swing over the top and start down the other side of the ball. I don't think boring bars were ever intended to take the forces in the direction that are being applied to them when used in a ball turner such as this. In the video I posted the link to, the tool being used has a radically different shape than that of a conventional boring bar. Have you done any experimenting with different shaped tool profiles, or are you getting good results with the inserted carbide tool you are using in your video?---Brian


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## velocette (May 2, 2014)

Hi
Personal preference for cutting tool is a round nosed HSS tool with 4 - 5 deg top rake,  6 - 7 deg front rake  and used upside down of course.
This will produce a very good finish on Stainless steel aluminum an mild steel. Take fairly light cuts and use cutting fluid.
I remove the toolpost and bolt the Ball Turner - Boring Head in is place. Just an idea that this may help for the smaller lathes.
The Housing was bored with the boring head mounted in the chuck so it is on the Centre Line.
A couple of photos show the boring head built from plans in "Model Engineers Workshop".

Eric


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## rodw (May 2, 2014)

Brian Rupnow said:


> RodW--I built a ball turner similar to yours today, using my boring head. It works quite well, but the brazed carbide boring tools I have leave a really ugly/nasty surface finish on the aluminum ball. ?....Have you done any experimenting with different shaped tool profiles, or are you getting good results with the inserted carbide tool you are using in your video?---Brian



Brian, I have alluded to the problem you noted. I have some  insert tool boring bars for my boring head but they have a flat on the shank which of course is on the wrong side so I reverted to the brazed tip stuff that I don't usually use. I think it is the last few  passes that set the final finish so slowing down and multiple passes helps, but yes, the sandpaper is necessary. 

Others I have seen have made a new boring bar with something with a fine tip like a DCMT tip that will cut happilly in both directions. Don't quote me that that is the right tip for the application. It would be worth reviewing that  video you posted to see how he did it. 

I had a look at the VMNG, VCMT and DCMT tips at my favourite Hong Kong supplier. I think the VMNG tip is probably the one to use as the cutting edges are square, not angled (does that mean no rake?) so they are probably better suited to an upside down orientation? 

I have some small CCMT06 tips which might be worth playing with but I am not confident I could  make a seat for them as I don't understand tool geometry.


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## Swifty (May 3, 2014)

Brian Rupnow said:


> Swifty--that isn't Chucketn. That's just a video I grabbed off youtube.---Brian



I realised that Brian, I just thought that I could see an accident about to happen.

Paul.


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## Brian Rupnow (May 3, 2014)

Rod--Have a look at my post titled "Boring Head-Ball Turner"--I designed a cutting tool and posted the design drawing and show the good results I got with it.---Brian


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## rodw (May 5, 2014)

Brian Rupnow said:


> Rod--Have a look at my post titled "Boring Head-Ball Turner"--I designed a cutting tool and posted the design drawing and show the good results I got with it.---Brian



Brian

Thanks. I did have a look at your ideas. I was wondering if it as worth looking at using a CCMT tool tip embedded in the end of a steel rod something like this:






The CCMT 06 has an 80 degree angle with 7 degrees of relief. I don't think it would be too hard to machine something like this up. You would still approach it from the side so you will make sure you get a ball not an egg. I think using the longitudinal feed with the tool on centre might be problematic making a ball as you would need another setup to start machining the back of the ball and make sure you stopped in the right place.

One day, I might give this a go. I think the cutting angles would work Ok.


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## Brian Rupnow (May 5, 2014)

Rod--I think that would work excellent. As far as approaching the ball--I think you have to approach it from the one end until half the ball is formed, then approach it from the other end until the other half ball is formed. As long as you set the tool height so that it matches the top of the piece when you have the handle straight up, no farther set up is necessary. Just don`t swing past center when forming either end. ---Brian


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## Omnimill (May 5, 2014)

Inserts are often used for ball turning but they use triangular or rhomboid inserts not square ones. I'm sure I've seen one with a triangular insert in the end of a bar for use on a boring head. The holder wasn't cranked though (why would you do that?) it was just a straight bar, although the insert may have been presented at a slight angle.

Not the one I've seen before but a similar design:

http://i207.photobucket.com/albums/bb93/blacksmithden/Radiustool-bitholder_zps24d0901a.jpg


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## rodw (May 5, 2014)

Brian Rupnow said:


> Rod--I think that would work excellent. As far as approaching the ball--I think you have to approach it from the one end until half the ball is formed, then approach it from the other end until the other half ball is formed. As long as you set the tool height so that it matches the top of the piece when you have the handle straight up, no farther set up is necessary. Just don`t swing past center when forming either end. ---Brian



Brian, thanks, the cutting edge of this tool would be the end of the rod so it is more suited to being fed from the side. well I think that is the case. I think this  replicates pretty closely what would happen if you use the same insert for turning.



Omnimill said:


> Inserts are often used for ball turning but they use triangular or rhomboid inserts not square ones. I'm sure I've seen one with a triangular insert in the end of a bar for use on a boring head. The holder wasn't cranked though (why would you do that?) it was just a straight bar, although the insert may have been presented at a slight angle.
> 
> Not the one I've seen before but a similar design:
> 
> http://i207.photobucket.com/albums/bb93/blacksmithden/Radiustool-bitholder_zps24d0901a.jpg



I looked at a couple of inserts I had on hand but chose the CCMT as I had a lot more of them! 

 The perspective of the drawing is deceiving, but the insert shown is a rhomboid shape. the tool is not actually cranked, just milled away for relief from a straight shaft. In practice, I don't think it will need to be machined as shown.

The key is to make sure the tool has the same geometry and can cut on each side. (I think). I did not want to have to order in another insert.


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## Omnimill (May 5, 2014)

The main reason folks choose triangular or Rhomboid is to give as much clearance as possible. Square should work fine though if that's what you have.

I chose the narrow inserts for my horizontal turner but want to use HSS as well when I get round to it.


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## rodw (May 6, 2014)

I dropped in on my mate Chris today and checked out how he made up the insert tooling and this became so simple I did not even draw it up.

I grabbed some 12mm bar stock and stuck it in a collet and swung the vice arud to 40 degrees






The angle of the tip is 80 degrees and 40 is half of that. That means the tip is able to be aligned so the radius of the bar passes through the centre of the insert tip.

Grabbed a milling head and cut the depth to about 2.4mm, which is roughly the thickness of the tip and milled away the end of the bar.






and drilled  hole which I tapped to M3





This is a really tight fit and the bolt has to screw into the insert.


And then I fitted the insert





I positioned the step in the rod and the hole by eye so the axis through the tool  centered. 

In my computer design, I milled the rod away so it was parallel with the tip. I think there is enough sticking out but if not, it is easy to fix this.

If this works, I might redo it with precise dimensions.

Sorry guys, that is as far as I got so you will wait until I try this out.


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## rodw (May 7, 2014)

Well, my new tool works very well. I still approached from the side. this works fine. I think the reason is that the inset has a 7 degree relief on the back side so it is  cutting out a triangular kerf so it does not bog down .

Before I used it, I scribed the edges of the insert, removed it and ground away the boring bar on my bench grinder to fully expose the sides of the cutting insert so I cold hog in the full width of the tip..

Here is the proof of the new tool. I think this is 3-4 times quicker and it leaves a much better finish.

[ame]https://www.youtube.com/watch?v=t-7Sh0iI3Mg[/ame]


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## chucketn (May 7, 2014)

Nice work, Rod. I'm still trying to re-configure my version to fit better on my 7x14. My first version works, but not as I want it to.

Chuck


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## Omnimill (May 7, 2014)

The finish looks good Rod. What's the clearance like cutting the other half like?


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## Brian Rupnow (May 7, 2014)

Rod--are you running your lathe in reverse during that video?--Brian


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## RonGinger (May 7, 2014)

Rod, I noticed you used one of those square collet blocks to hold the bit while you cut the end. I just cam down from my shop to take a break, but the last job I did was to carefully measure my square block to see if the rod is on center- it is not, by over .005" I put a drill blank in a collet and ran over it with an indicator, then rotated the block to all 4 sides. I am very unhappy to see this error but it accounts for some trouble I have had in the past that work done with the block was not accurate.

For the job you just did it would not matter, but if you expect the block to hold stock on center you had better check it.

Anyone want to buy a nice collet block, cheap?


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## chucketn (May 7, 2014)

Ron G., what type of collet block and where did you get it? I ask, because my next tool investment will be a set of ER32 collets, chucks, and a set of  ER32 collet blocks.
And for RodW, what kind of lathe do you have? It may have been posted, but I missed it.

Chuck


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## Omnimill (May 7, 2014)

I suppose it depends on how you use these blocks. .005" off wouldn't make any difference for the stuff I've done, especially since I probably zeroed each time I rotated the block anyway. I doubt I could afford a set if they were spot on.


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## rodw (May 7, 2014)

Thanks for your interest guys.



Omnimill said:


> The finish looks good Rod. What's the clearance like cutting the other half like?



I have not checked that but I don't expect any problems.  I made a couple of measurements before I cut the boring bar to length. Its the length of the boring bar and how far back which you can get the cross slide which determines how big a ball you can cut, I made this bar a bit shorter than the one I used before so to let me move back a bit so it shoukd be able to cut a 60mm ball or so.



Brian Rupnow said:


> Rod--are you running your lathe in reverse during that video?--Brian



No Brian. After breaking my camcorder on the first video I borrowed my wife's still camera and it picked the wrong focus point which might contribute to the illusion. I think the tool geometry we both use is similar, but the difference is the relief at the back which lets mine enter from the side happilly.




chucketn said:


> Ron G., what type of collet block and where did you get it? I ask, because my next tool investment will be a set of ER32 collets, chucks, and a set of  ER32 collet blocks.
> And for RodW, what kind of lathe do you have? It may have been posted, but I missed it.
> 
> Chuck



Chuck, I have both ER32 and 5C collets (metric and Imperial). The lathe is an AL320G (13" swing) from http://www.machineryhouse.com.au/L141 
This lathe has a 38mm spindle and I have bought the 5C block  set (square and hex blocks) and a 5C collet adapter for it that threads through the spindle from the same guys. See http://www.machineryhouse.com.au/C980

I use the 5C collets in both my lathe and collet blocks but hold any milling tools in the ER32.

Most of the collets I have purchased from CTC tools but the imperial 5Cs came from Little Machine Shop. One day I will get some of the hex collets.

RonGinger, I did do some runout tests on my lathe and the collett adapter but not  the collett blocks. What I found was the lathe spindle taper itself is spot on, zero runout, but the 3 jaw chuck and collets add some runout but still within acceptble specs I found on the net. I think the moral to the story is that every time you add an adapter, you add error.

I hope I answered everybody's questions. I am quite amazed with the interest this thread has aroused.


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## RonGinger (May 7, 2014)

I do not know the source of my collet block set, I have had them for many years, but this was the first time I thought to actually measure the runout. I have used them to make a flat or rectangular shape on round parts. I was about to make the connection rod end for Gerrys Beam engine. I had made one previously but it did not come out exactly centred on teh round part, hence my checking.

I guess they are still useable if I re-zero on each surface every time I reposition the blocks. I will check the hex block later today when I get back to the shop.


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## rodw (May 7, 2014)

Just an update here after a bit more playing machining the back side of the ball. The choice of screw I used impacts on clearance when feeding from the side. Because it protrudes from the front face, it fouls the spindle before you can cut do depth. With the tool in the centre position, this is not an issue. This means it will work fine if you use Brian's approach and feed the tool in longitudinally.

I tried to replace the mounting screw with a countersunk one but you would need to use an M2.5 screw as the better quality countersunk screw I had was too big to fit through the insert tip. If you use the correct screw for the insert tip, there will be no clearance issues as the flat face of the tool will allow the cutting tip to touch the spindle.

When I get to it, I will redraw it with some accurate dimensions and make a new tool based on my learnings.

The finish I achieved today was fantastic and I was able to proceed quickly to a mirror finish skipping the 240 grit I used previously and starting at 400 grit wet and dry.


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## rodw (May 7, 2014)

RonGinger said:


> I do not know the source of my collet block set, I have had them for many years, but this was the first time I thought to actually measure the runout. I have used them to make a flat or rectangular shape on round parts. I was about to make the connection rod end for Gerrys Beam engine. I had made one previously but it did not come out exactly centred on teh round part, hence my checking.
> 
> I guess they are still useable if I re-zero on each surface every time I reposition the blocks. I will check the hex block later today when I get back to the shop.



I might try setting mine up in my vice and see what the coaxial indicator says as I rotate the blocks. I guess if you know the error, you'd only need to offset the mill table a smidgen. Maybe stamp the adjustment on them.


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## velocette (May 8, 2014)

Hi 
One thing that I observe watching video of a "Boring Bar - Ball Turner" is that moving the cross slide to the bar stock in the chuck gives some horrible angles for the tool tip to work to.
Not until the tool is advanced to be on centre line both vertical and horizontal does it peel off a continued chip stream.
""Omnimill"" with a vertical piviot is a different story with no change in the cutting angle attack.
Surely for the "Boring Bar" approach is the the piviot must move down on to the work on the vertical plane having the boring bar Piviot mounted in a Vertical slide and on vertical centre line.
OR
Advance by adjusting the boring bar radius closer to the centre of it's piviot until the desired diameter is reached.

Eric


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## Wizard69 (May 13, 2014)

RonGinger said:


> I do not know the source of my collet block set, I have had them for many years, but this was the first time I thought to actually measure the runout. I have used them to make a flat or rectangular shape on round parts. I was about to make the connection rod end for Gerrys Beam engine. I had made one previously but it did not come out exactly centred on teh round part, hence my checking.
> 
> I guess they are still useable if I re-zero on each surface every time I reposition the blocks. I will check the hex block later today when I get back to the shop.




If anybody does have a source for accurate collet blocks please inform the group.   I've run into similar problems pith a set of collet block I have. 


Sent from my iPad using Model Engines


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## castlead (May 15, 2014)

I have been using boring heads to make knobs for years.  However I use a mill, boring head, and an indexer.  You set the boring head with cutter turned inboard same as you would to "turn" a post. You set the indexer at the angle where the apex of sphere and diameter of shaft holding your work piece so they are on the same plane. Edge find the piece so you are centered in the full sphere axis and centered less the chord of circle in the axis with shaft sticking out. Turn the mill on in reverse (cutter is facing inboard remember) lower qwill into work a bit, and index 360. Repeat until you have a sphere. Variations of this can produce acorn shapes, dished edges and other artistic designs. You must be gentile, as if too aggressive you can unscrew the boring head from its adapter.   I would assume the same could be done in the lathe with the boring head in the chuck and using the compound to set the angle, provided you have a provision to rotate the work piece.


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## rodw (Jun 5, 2014)

Just a bit of an update after I have cut a few more radiuses. I think Brian is right. It is better to centre the tool and approach along the Longitudinal axis. I found it is pretty easy to zero my DRO with the ball turner in its final position so I know when I have advanced into the ball enough but a carriage stop would also be useful.

Finally, my polishing has progressed a bit. Yesterday, I just used wet and dry sand paper with the coolant trickling on the part instead of kerosene as a lubricant. There was no difference in the final result though.

Finally if you have a ball on a threaded mandrel and you can't remove it after turning and polishing, try wrapping the part in Glad Wrap (eg. Cling wrap). Worked a treat and let me get a good grip without marring the finish.

I made myself a coffee tamper yesterday and it came up a treat in polished aluminium. Two pieces with a threaded handle. I bought a piece of stainless steel bar today and have ordered some turning and parting inserts to see if I can remake the base in stainless steel. $300 a metre Ouch! Anyway, I only bought 150mm (6"). The tricky bit will be to centre drill and tap a hole in the base for the handle to screw into. I ordered an ER32 tapping collet that has a built in clutch to prevent breaking a tap when it bottoms out so I might mount the base in my rotary table chuck and try drilling and tapping on my SX3 mill. I'll post some pics of the completed part as the tapered handle is a really nice idea if you want something different.


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