# Powermatic/Burke mill



## ksouers (Sep 29, 2008)

I have an opportunity to buy a Powermatic/Burke knee mill, looks to be from the 1970's.

The table is 8x32, plenty big enough for me. But it has a 3 phase motor.
I don't want to get a rotary converter (another $500 or so) so I'm thinking of either replacing the motor with a single phase or having the existing motor rewound for single.

Does anyone know anything about these machines?

I'm guessing I will lose some torque by going to single phase, but the HP should be similar. Any thoughts?


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## kvom (Sep 29, 2008)

Rather than a RPC, why not get a VFD? You get 3 phase plus variable speed without changing belts.


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## ksouers (Sep 29, 2008)

I thought of that, but if I recall it cuts the power to something like 66% doesn't it?


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## wareagle (Sep 29, 2008)

Anytime you power a 3 phase motor with a single phase power source there will be a loss of efficiency and the output power of the motor will be reduced. Your options for converting power from single phase to three phase are as follows:

Static phase converter: These units are fairly inexpensive and are easily installed. With this unit you can expect to have only two-thirds the rated HP of the motor (i.e. a 3HP motor will now be effectively 2HP).






Rotary phase converter: These units are advertised to provide 100% of the motor's rating and torque. In reality, this isn't the case, but they do perform much better than the static converters. I don't have and exact loss, in other words this is a SWAG, but with a RPC you can expect between 90-95% of the motors rating. The drawback is these units are expensive. One can be built out of an old motor, but if you choose to do this, be sure to fully understand the implications of the project before deciding to do that. I just built one for a friend and the cost of it was about 30% less than buying a manufactured unit, and he already had the motor.





Inverter/VFD: This is my personal favorite. You get a lot of bang for the buck out of these units. I put one on my milling machine, and it has performed very well. You will get an infinite control of you motor's speed, and that can greatly enhance your abilities to get great finishes. It is also very nice for not having to change belts each time a speed change is required. The drawback is you do loose some off of the rating of the motor with these units. My SWAG here is you will get around 85-90% of the motor's rating. THere is also some time that will be needed to make the programming work in your application, and that can be tricky. It is doable, and there are plenty here that can help you with that.





Hopefully this will give you some food for thought. When I first was using my mill, I had a static converter on it. It worked, but since putting the VFD on, it has made it a totally different machine. The price of the VFD was a bit less that twice the price of the static converter, but it performs many times better than the SPC in my experience.

A word on building your own RTC if you choose to go that route... I would advise against it. The unit I just finished for my friend works very well, but for the amount of money it took to buy all of the required components along with time it took to put it together and basically tune it out really makes this option non-attractive. Had he needed to buy a motor for his project, he would have spent more than buying a premade unit!! I did not charge him for labor, but my time invested in the project was about 10 hours.


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## ksouers (Sep 29, 2008)

Thanks W/E.
That was a lot of great information. Electricity is magic to me so it was excellent to see a comparison of the various converter solutions.
It looks like the VFD is the way to go, about the same price or a little cheaper than re-powering and I get to keep the 3 phase. The machine only has 1 HP, I think can live with the 15% loss.


Does anyone have any knowledge of the machine itself?
What are the weak points?
What should I look for?


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## zeusrekning (Sep 29, 2008)

I would say strongly to stay away from the static converter. I tried one with my series 1 bridgeport 1hp. It was like single pahsing a motor. I could stop the spindle by grabbing the chuck. I lucked out and found a old but unused 10hp Rotory converter. Hooked it up and runs great. Wish I had the VFD but cost was my issue. I hate changing belt. :-[
Tim


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## CrewCab (Sep 29, 2008)

I've just fitted an Inverter/VFD to run my 3 Phase Boxford Lathe, now the wiring is sorted to the correct configuration : it really has made the lathe come alive plus, the variable speed and (almost) instant reverse is a nice bonus.





CC


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## ksouers (Sep 29, 2008)

Thanks for the replys guys.

You've convinced me that the VFD is the way to go.

CC,
That looks great! I like that reversable feature, though I don't see much use for it on a mill. But the quick stop would be a plus. What brand VFD did you use? American? Brit? Jap? Other?


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## CrewCab (Sep 29, 2008)

True Kevin, reverse on the Mill is about as useful as a chocolate fire guard  

Mine is the same make as WarEagle's a TECO they are Taiwanese and seem well regarded, I didn't specifically go looking for that make, the company I bought it off was recommended to me by another forum member and I followed their advice, it wasn't the cheapest but then again it wasn't a much dearer than the cheapeast option (about £30 / $60 more) including the Remote controller total cost was a little over £200 but over your side of the pond they seem to be available at far better prices .........  

*For Instance* .............. although that is a 1HP unit, fine for me as my lathe is only .75HP, you may want to go a little bigger, do a trawl and see what comes up.


Apparently they can be programmed to stop instantly, but I think that could just cause the chuck to unscrew ??? .......... so I've set it for about 3 seconds deceleration time at the present, plus a little longer to accelerate fire up ............ gives the Old Gal' time to warm up gently 8)


hth

CC


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## ksouers (Sep 29, 2008)

Thanks CC.

I did the Google earlier with W/E's post, came up with the same vendor you did.
The prices are very reasonable, I think. About the same price as swapping out for a single phase motor, assuming I could find one to fit the machine. Maybe cheaper. A friend, a purchasing agent for a local shop, suggested getting the current motor re-wound for single phase, but that would still cost about the same as replacing the motor.

Now that I have the power squared away I guess I better go look at the machine and start clearing out some space in the shop.


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## wareagle (Sep 29, 2008)

I will add that these VFDs can be tricky to get programmed. They are suited for a variety of different applications, and setting the parameters to suit the needs of a machine tool can seen daunting. If you decide to buy one, take your time to read and most importantly understand the instructions before you install your drive. This is the best piece of advise I can give to anyone who is considering installing one of these units on their machine.

One last thing, don't let the complexity of the devices turn you away. Though they can be tricky on the programming, once running they really are a dream!!


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## kvom (Sep 29, 2008)

I bought the 2HP GS2 from AutomationDirect, whose warehouse is a couple of miles from my house. It's made in China, so possible available in OZ as well. My cost was about $235. It has one nice feature which allows the belt ratio of the mill to be entered and factored against the motor speed so that the displayed number is the spindle speed. It also has a detachable control panel that can be remoted to the base unit with a cable, so that the box can be mounted on the wall and the controls on the mill.

Some facts I've gleaned about VFDs:

1) Don't use the mill's on-off switch while the VFD is operating. It can cause the VFD to fail. In fact, removing the switch from between the VFD and the motor is recommended.

2) Don't use the mill's spindle brake; let the VFD stop the spindle.

3) If the VFD doesn't stop the rotation fast enough to suit, you can connect braking resistors to the VFD. These absorb the reflected energy from the motor.

As for reverse, it is useful when you are using the mill to tap. In reverse it withdraws the tap. Also, if the mill has a backgear engaged, then you need to run the motor in reverse.


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## kennyd (Sep 29, 2008)

Another vote here for a VFD. I put one on my Clausing lathe and is a beautiful thing not to have to change the belts all the time!

Here are some pictures of my re-build:
http://picasaweb.google.com/kdeckster/Clausing4900#


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## wareagle (Sep 29, 2008)

kennyd, that is a great restoration!  :bow:

My lathe has a single phase motor currently, but in the event it decides to go to the motor heavens, then I will likely fit mine with a VFD set up!


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## ksouers (Sep 29, 2008)

Kenny, that's some rebuild! Looks great!

kvom, thanks for the tips. I'll definitely put them to use.

Where do you guys keep your belts stationed with the VFD? Something close to the middle, 1:1?


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## CrewCab (Sep 29, 2008)

wareagle  said:
			
		

> kennyd, that is a great restoration! :bow:



Got to agree ............. cracking job 8)

CC


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## kennyd (Sep 29, 2008)

wareagle  said:
			
		

> kennyd, that is a great restoration! :bow:
> 
> My lathe has a single phase motor currently, but in the event it decides to go to the motor heavens, then I will likely fit mine with a VFD set up!



Thank you :-[


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## kennyd (Sep 29, 2008)

ksouers  said:
			
		

> Kenny, that's some rebuild! Looks great!
> 
> kvom, thanks for the tips. I'll definitely put them to use.
> 
> Where do you guys keep your belts stationed with the VFD? Something close to the middle, 1:1?



My belt is usually on the first pulley, which is 370rpm open and 52rpm in back gear. It has suited me for the small projects I've done so far-I am just a rank amateur!


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## kennyd (Sep 29, 2008)

> Got to agree ............. cracking job Cool


Thank you also :-[


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## steamer (Sep 29, 2008)

Hi, 

Noticed the thread about SPC and RPC.  

I bought the Phase -0-matic static one for my Logan Lathe

Problem, the motor would still pull enough to pop the breaker on the lathe because the legs that were working were pulling too much.

What I did was to make the RPC using the Phase-o-matic. The SPC gets the idler motor running and then I run the lathe from the idler motor. You will need a momemtary on switch. A schematic was part of the installation instructions that cam with the PHM. I bought a used 3 hp ( 50% larger than load) motor/pump from a motor house for $50, and with some wiring...It worked fine.

Dave 

PS if you look inside a Phase-o-matic you will want to puke.....there are about 3 parts and some cardboard....no magic there.  Get the Heavy Duty as the standard duty if overloaded at all will pop and it's done. The HD unit has heavier components and is a bit more forgiving.  But in all, they get a lot of money for what their selling.


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## ksouers (Sep 29, 2008)

Thanks for everyone's input on the motor issue. It is greatly appreciated :bow:


Does anyone have an opinion on the mill? Are they any good?
Should I take a look or just walk away from it?


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## steamer (Sep 29, 2008)

Hi Ksouers,

Can't give specifics about a Powermatic/Burke. I have a Logan/Powermatic lathe in that wonderful green and I love my lathe....some of the handwheels are kinda cheesy, but it turns straight.

You can make good parts with a worn lathe, but it's almost impossible to make good parts with a worn mill

Check the ways for wear. Check the squareness of the table to the spindle left to right and front to back

Do these checks with the ways locked and unlocked.

Also check the spindle taper for run-out

If all of that falls within your goodness criteria, and the spindle bearings don't sound like a clothes washer on spin cycle, it may be a good mill.

All these checks can be done with a dial indicator and a indicator stand/arm.

I was looking at a pristine Rockwell mill in just such a way as it is significantly smaller than my VN#12 and would be more suited to my future projects. In any case and to my amazement, the spindle was out .002" over the width of the table.  It was scraped in that way! Go figure?


Do you have any pictures?


Dave


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## ksouers (Sep 29, 2008)

The only picture I have is the little cheesy one posted on Craig's List.







It has some rust, but it just looks like a patina/surface rust. Won't really know till I take a good look at it.

I had already planned to check it out with a DTI, all the usual stuff. Also taking a machinist friend along to get his opinion.

I was wondering if anyone had any experience with this brand of mill. I've seen mills like this before but I've never used one, so I really don't know anything about them. I don't know if the thing is really flimsy or quite solid. It looks a little light weight, but it could still be quite solid and stable. I just don't know.


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## kennyd (Sep 30, 2008)

I have heard good things about them...And I keep waiting for one to show up in my area. Some of them I think (unless I am confusing it with the Clausing mill that looks similar) did not have R8 collets witch could be a problem getting tooling later-so check to make sure what collets it uses.

Whats the asking price?
What tooling is included?


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## ksouers (Sep 30, 2008)

Thanks Kenny. I haven't heard anything about them so I'm totally in the dark about their reputation.
Well, we'll see how it turns out. Talked to the guy today, it's been "lightly used" since he bought it. He mostly uses it as a backup for his Bridgeport. We go Friday for a look-see. It's really close to home, about 2 miles from my office, then another 10 home.

It comes with a Bridgeport vise, in the pics it looks like a re-badged Kurt, could just be a clone. We'll see. Also a couple of collets. It has an R8 spindle. I'm not worried about tooling as my current mill is also R8. Though I'll probably end up needing to make some new T-nuts for clamping.

The guy's asking $1600 USD, I'm going to offer less and see if he bites. I really want a Bridgy but they don't show up often around here. Those that do are usually newer and commanding a price more than I'm willing to pay for a hobby machine. Though with the economy tanking I should wait a couple months. I don't mean to sound like a vulture, don't want to see anyone lose their business.


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## kennyd (Sep 30, 2008)

That is about the price I have seen them go for also...I am interested in one because my shop is in the basement with only stairwell access.

If you want/need a Bridgeport though...this is no substitute!


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## CrewCab (Sep 30, 2008)

So ................. just as a matter of interest guys .............. would this have been a good buy for this side of the pond ....&#160; 

>>  <<

CC


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## ksouers (Sep 30, 2008)

CC,
Using the common $2 per GBP I'd say that was a very good price. I doubt that would've gone so cheaply here, maybe 1000 to 1500 GBP.
But I don't know what the esoteric value of a pound is. Dinner out tonight for me and the wife was $25 plus tip, call it $29 USD, at a local theme-type chain restaurant. Would 15 GBP sound right for a dinner for two? If 15 GBP was high, then the cost of the Bridgy was probably high.

Kenny,
Sorry, didn't mean to give the wrong impression. I don't expect this to be a match for a Bridgeport. Nor do I absolutely need one. I'd just like to have one. As long as this thing is better quality than a comparably classed import I'll be satisfied. At this point I'm really not willing to spend $3000-$5000 for a machine that will most likely only make parts for a hobby. I'm also fully prepared to walk away from it.


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## kennyd (Oct 1, 2008)

ksouers  said:
			
		

> Kenny,
> Sorry, didn't mean to give the wrong impression. I don't expect this to be a match for a Bridgeport. Nor do I absolutely need one. I'd just like to have one. As long as this thing is better quality than a comparably classed import I'll be satisfied. At this point I'm really not willing to spend $3000-$5000 for a machine that will most likely only make parts for a hobby. I'm also fully prepared to walk away from it.



Understood 

I want one to replace my POS grizzly mill/drill (no offense intended to those who also have one )


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## ksouers (Oct 1, 2008)

kennyd  said:
			
		

> Understood
> 
> I want one to replace my POS grizzly mill/drill (no offense intended to those who also have one )



That's my intention as well, to replace my X2. It would also be nice if I could get a little side work with it, maybe shaving some motorcycle heads or something.


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## CrewCab (Oct 1, 2008)

ksouers  said:
			
		

> Would 15 GBP sound right for a dinner for two? If 15 GBP was high, then the cost of the Bridgy was probably high.



You can get 2 meals for about £15 GBP ............ it is around the bottom end of the price range though, don't get me wrong. we have a local Pub that does 2 for 1 and ain't bad for the price, but the kitchen is staffed by "Microwave Technician's", doubt there is a chef in sight .............. I'd say on average, a reasonable meal for 2, without going over the top is nearer £30  ................. heck it cost's us £20 for a Chinese take out for 2 ???

CC


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## ksouers (Oct 1, 2008)

Then it sounds like that was a really good price for that mill. Why'd you let it get away??? ;D


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## CrewCab (Oct 1, 2008)

ksouers  said:
			
		

> Why'd you let it get away??? ;D



No room mate  , plus ................ I've spent mi' budget (and a bit more) on the "spare" lathe, .............. best I sell one soon before SWMBO realises there are two ;D .............. fortunately ............. all things mechanical look the same to Mrs CC :

CC


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## Maryak (Oct 1, 2008)

CrewCab  said:
			
		

> .............. fortunately ............. all things mechanical look the same to Mrs CC :
> 
> CC



Lucky You,


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## ksouers (Oct 1, 2008)

CrewCab  said:
			
		

> No room mate  , plus ................ I've spent mi' budget (and a bit more) on the "spare" lathe, .............. best I sell one soon before SWMBO realises there are two ;D .............. fortunately ............. all things mechanical look the same to Mrs CC :
> 
> CC



I fully understand the room issue. If this mill follows me home I'm going to have tough time finding a place for it. My shop is roughly 6 or 7 square meters. I guess I'll need almost 3 square of it for the mill ???

My missus see all machinery the same way as well. Unfortunately she does know how to count!


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## ksouers (Oct 3, 2008)

Well, I did it!

I bought the mill. Just got back from looking it over and talking with they guy. Took my friend Dan along. Dan is another ex-machinist with more experience than me. He agreed the machine is in great shape.

What looks like rust in the pictures is just that lovely patina that well aged cast iron gets that actually helps prevent rust. The real selling point for me was that on the ways all the original scrape marks were still quite visible.

Yes, it has some accumulated grime, that'll clean up easy enough. Everything worked very smooth. No doubt with a little degreasing and fresh lube it'll be even smoother. And it runs dead quiet! Dan put a rod to the spindle to listen to the bearings and said it was dead quiet. No clanking, not even a little.

We are arranging transportation this weekend, should have it in the shop and have better pictures by Monday or Tuesday.

Finally, some American Iron in my shop!


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## wareagle (Oct 4, 2008)

Congrats! That is great, and it sounds like you found an excellent machine!!

_Serious tool aquisition envy...._


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## ksouers (Oct 4, 2008)

Thanks W/E.
And especially thanks for the advice on the different options for powering it. That was extremely helpful. I'm going to order the inverter this week, should have it under power by next week.


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## CrewCab (Oct 4, 2008)

Nice one Kevin 8) .............. sounds like you've got a good one there .......... please keep us updated 

Cheers

CC


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## rick9345 (Dec 21, 2014)

ksouers said:


> Thanks for the replys guys.
> 
> You've convinced me that the VFD is the way to go.
> 
> ...



Quick hole Tapping  unless you have a tapping head, but use a key type drill chuck, keyless will loosen when reversed and will have to back tap out by hand


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