CNCing an older lathe

[BrassBuilder]

Fellow CNCers,
I am in a dilema and not sure what to do...

I have a Clausing 100 mk3a lathe from about 1945. This eventually became the Atlas 4800 when Atlas took over the company. I bought my lathe on ebay for $1000 a couple of years ago. It works well as a manual lathe, but after I got my mill CNCd (thanks to help on the board), I am getting the urge to CNC *a* lathe.

http://www.lathes.co.uk/clausing/page13.html

I have the 7x14 Cummins lathe that I took apart and started to use it to build a 4th axis for my x2 mill...that is about half done, but won't be big enough to turn some of the parts that I need to turn....hence buying a 12" lathe. Plus I really want a stand-alone CNC lathe anyway without having to switch the mill over to the lathe portion.

It *almost* seems sacreligious (sp??) to CNC this one. But the problem is that the machine is missing the original motor mount and the countershaft (the one that has the pulley on it that runs off the motor) is worn. I have been searching almost two years for these two parts and cannot find them. Granted, the lathe works yet with the worn countershaft and the homemade motor mount, but my intension was to restore this. I pretty much gave up looking for parts.

I also entertained the notion of selling the Clausing and buying a new chinese lathe, but at $2000 (or more) for a 12" lathe and having to throw most of the parts away anyway, that does not seem like a viable option either. I also do not think I will get my $1000 back as I will sell this one with a better description to the problems. I think I would be lucky to get over half my money back.

I was looking at parts on ebay and came across this ball screw and bearings:

http://cgi.ebay.com/LINEAR-BEARING-T...4.c0.m14.l1262

I was going to mount these down the side of the bed and make a new mount to control the apron and then find parts for the cross slide.

I also want to regear this because it only spins at about 800 rpm for top speed. The headstock already has Timken bearings. I figure the headstock should be good for a couple thousand RPMs.

The parts that I don't need (and there will be quite a few) will get resold on ebay. They will pay for a good chunk of that $400 for the rails and ballscrew posted above. Then lathe will NOT be restorable once I am done with it...

I am thinking a NEMA 34 motor to control the apron. I know I will need something pretty good sized.

So...Do I CNC this? What do you think?

Constructive critisism welcomed.

Mike

[BrassBuilder]

Alrighty....
Let's take this a different direction....

I've been shopping around for parts. What do you think of this shopping list?

From Kelling:
A:2 PCS KL-9082, 24V-90V, 8.2A Bipolar Driver
http://www.kelinginc.net/KLDriver.html

B: 1 PCS NEMA 34- Stepper Motors, KL34H295-43-8A
http://www.kelinginc.net/NEMA34Motor.html (item 4)


1 PCS NEMA 42- Stepper Motors,KL-42H2150-42-8A
http://www.kelinginc.net/NEMA42Motor.html

C: 1 PCS KL-7220, 72V(No load), Max 20A,Unregulated Power
Supply, 110V/220V
http://www.kelinginc.net/SwitchingPowerSupply.html (just past the "LINKS" button)

D:1 PCS C10 Breakout board, E-Stop or Limit Switch can be wired
http://www.kelinginc.net/BreakoutBoards.html

E: 5V Power Supply for Breakout Board


From Ebay for the Z axis:
http://cgi.ebay.com/LINEAR-BEARING-T...4.c0.m14.l1262

How is this list looking for CNCing the above machine? I got the Keling list from Keling through an email asking for their recommendations. I was thinking of going for the C11 BOB instead of the C10 though.

They did not have a part number listed for the 5V power supply.

I'm drawing a rather crude drawing of what I have planned for this lathe. I'll post it as soon as I git-r- done.

I still need to find a ballscrew for the X axis.

Thanks
Mike

[BrassBuilder]

Pictures:

Before and after. Forgive me for the crudeness of the after picture. But I think it will give you the general idea of what I am looking at. I can reuse the whole top of the apron. I will build a new box for the bottom out probably 3/4" x 6" 6061 aluminum. The main piece going across the front will probably also be 3/4" x 6" 6061 aluminum. The two all black things are the THK rails. The black thing with the gray squiggly lines is the ballscrew. The four red blocks are the THK rail blocks. The red block on the right hand side is the ballscrew mount. I would have to design it so that the aluminum on the apron would bolt into the rail blocks.

I'll have to build mounts for the NEMA 42 motor for the Z. Could I go direct drive? Or would a reduction belt drive be better?

I need some input...
Mike

[TOTALLYRC]

Originally Posted by BrassBuilder Pictures: Before and after. Forgive me for the crudeness of the after picture. But I think it will give you the general idea of what I am looking at. I can reuse the whole top of the apron. I will build a new box for the bottom out probably 3/4" x 6" 6061 aluminum. The main piece going across the front will probably also be 3/4" x 6" 6061 aluminum. The two all black things are the THK rails. The black thing with the gray squiggly lines is the ballscrew. The four red blocks are the THK rail blocks. The red block on the right hand side is the ballscrew mount. I would have to design it so that the aluminum on the apron would bolt into the rail blocks. I'll have to build mounts for the NEMA 42 motor for the Z. Could I go direct drive? Or would a reduction belt drive be better? I need some input... Mike

Hi Mike,
A couple of things come to mind in no particular order.

1.If the lathe is a 12" lathe I don't see the need for a nema 42 on either axis.

2. If those drivers don't offer mid band compensation, and I think they don't, consider the Gecko G203v since they do and are almost bullet proof. 80v absolute max. They also morph from micro to full steps on the fly allowing for more torque at high speeds.

3. I don't see the need for the linear rails to drive the Z axis, just the ball screw and some way to shield it would be sufficient. The ways of the lathe should do all the work as far as aligning the carriage, just as if it was still a manual lathe.

4. As fas as do you CNC this or not is entirely up to you. If it is not worth a whole bunch on the open market, why not?

5. Direct drive should be OK depending on the screw pitch for both axis's.

6. Have fun.

What will you be using for CNC software?

[BrassBuilder]

Thanks for the reply!

1. I based the NEMA 42 on a kit supplied by this company: http://www.microkinetics.com/conv_kits/index.htm and when I emailed Keling, they recommended the 42 too. The X axis has a NEMA 34.

2. I'll have to look into this. I am not sure what mid-band support is. I was looking at Gecko drives but I did not see anything that would run a NEMA 42 stepper. I'll take another look at the G203V.

3. I was wondering about the rails too...it was in the back of my mind that the ways should be fine. This is good since it will save a lot of money by not having to buy the rails.

4. Yeah. I came to the same conclusion. And wouldn't a CNCd 1945 lathe be cool anyway? LOL Plus some of the parts that I don't need will help keep other of these lathes going.

5. I thought so...but was not sure if there was an advantage to a belt/chain drive system.

6. That I am!

I am using Mach 3 for the CNC. I am already running that on the mill. I am using Dolphin CAD for the drawing part right now, but have Alibre Design Expert that I am trying to learn.

Thanks again.
Mike

[TOTALLYRC]

Replies are easy, correct replies cost more

#1. I still don't see the need but I can't give a real reason other than I think it is overkill. It "feels" like it might limit your rapids, but don't take my word for it.

#2. Mid band resonance compensation. Steppers tend to go into resonance and the compensation electronically helps prevent stalls and missed steps. It can also be done mechanically with a "rattler" attached to the motor.

#3.Saving money is a good thing.

#4. I had a vintage 1920"s lathe but is was worth more sold to somebody else than as a conversion. Old Cast iron is good Iron. Of course as long as the machine is not worn out. The one caveat to all of this is that if it was a lousy machine when used manually, converting it to CNC is not going to make it better.

#5. Belt drive allows for fine tuning the final drive ratios, allowing for better matching of the motors characteristics with the speeds and force needed. With direct drive it is what it is.

#6. Me too.

I also use Mach 3 for my mill, and will be using Mach turn for my lathe when it is up and running.

[BrassBuilder]

I've been searching for just a ballscrew on ebay and I see most of them are metric verses inch measurements. Is that going to matter? I suppose I would want the Z and X axis the same ratio though...i.e. use both metric or both inch?

Mike

[Al_The_Man]

When I converted a slightly smaller lathe I replace the bolt on carriage front with a small section of deep web channel iron, it was an exact fit, widthwise, I mounted the ball screw nut inside the apron.
If does not really matter on the resolution or whether they are the same as they can be scaled.
I generally do not go over .25" pitch for servo's.
I was lucky enough to get a small dia ballscrew from some equipment I bought that replaced the existing cross slide screw under the cross slide.
I put a QC tool post on and as I did not need the compound rest with CNC, this allowed me to put on one size larger QC post for extra rigidity.
Al.

[BrassBuilder]

Originally Posted by Al_The_Man When I converted a slightly smaller lathe I replace the bolt on carriage front with a small section of deep web channel iron, it was an exact fit, widthwise, I mounted the ball screw nut inside the apron. If does not really matter on the resolution or whether they are the same as they can be scaled. I generally do not go over .25" pitch for servo's. I was lucky enough to get a small dia ballscrew from some equipment I bought that replaced the existing cross slide screw under the cross slide. I put a QC tool post on and as I did not need the compound rest with CNC, this allowed me to put on one size larger QC post for extra rigidity. Al.

My current leadscrew is 3/4". Do I need to find one at least that size? I am finding a lot of 1/2" to 5/8" or 12-16mm. How big of a deal is that?

If I understand correctly...it does not matter if I go with metric or inch ballscrews?
Thanks for the reply.
Mike

[Al_The_Man]

On that size of lathe it is not unusual to see 3/4" to 1" BS, I would tend to go with at least 3/4" if possible.
It is surprising how much whip you can get on high rapids even though the nut is supported.
I have a 20mm, 5mm pitch on a 9x30.
Al.

[BrassBuilder]

Wow...I've been searching around ebay and I am not sure what I need now. I've been looking at Roton now for new ballscrews and that might be the way to go. Take a look at this:

http://www.roton.com/Mating_Componen...mber=59305&#PN

I'm looking at 48" of ballscrew, one of the round ballnuts, and one of the mounting flanges. Total is just over $200.

The ballscrews come in LH and RH. RH seems to be more popular and that is what I was going to go with. They come in 1x.250, 1x.333, 1x.500...etc...I went with the 1x.250.

Where do I find the end blocks for the support? Roton does not seem to carry them.

Anyone knows of dealers that sell complete used setups?

Thanks
Mike

[Al_The_Man]

I got most of my hardware from Misumi USA, send for their catalogue, its worth it.
Al.