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Myford Super 7 - adding ball screws
« on: September 06, 2012, 10:40:56 AM »
Hi folks, after a lot of thought I have decided that using plain screws on my lathe conversion is never going to give good results, and as far as I can see after a little experimentation I'm not going to be able to apply backlash compensation because the play in at least the Z leadscrew is too large.  So, has anyone got any experience of replacing the myford screws with ballscrews please?  Or could point me to info on the web?

I think I can see how to do it on the crossslide without too much trouble, but getting a long Z screw aligned with the nut on the saddle, and mounting the nut, has me stumped for now.  Another problem will be protecting the screws from chips.

Thanks in advance!

John.
Re: Myford Super 7 - adding ball screws
« Reply #1 on: September 06, 2012, 02:53:43 PM »
Hi John,

I have been working on a similar project to fit a Southbend 9" with steppers and yes the leadscrew is the more challeging axis to eliminate/reduce the back lash. I choose to use low back lash nuts but often toy with the idea of ballscrews. Because I want to toggle between conventional and CNC use I will make due with poor mans method of backlash reduction. Maybe you should post a picture of your lathe, particularly the carriage & lead screw shot to stimulate some of our resident guru's ideas on how to interface a ball on the long screw. Picture says 1000 words or thereabouts.

Robert

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Re: Myford Super 7 - adding ball screws
« Reply #2 on: September 06, 2012, 04:17:21 PM »
The wee lathe I am updating at the moment is based on a Myford ML10 so not sure if that will help or not.
Hood
Re: Myford Super 7 - adding ball screws
« Reply #3 on: September 06, 2012, 05:07:13 PM »
The wee lathe I am updating at the moment is based on a Myford ML10 so not sure if that will help or not.
Hood

That's a sweet baby retro project Hood!

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Re: Myford Super 7 - adding ball screws
« Reply #4 on: September 06, 2012, 05:11:32 PM »
Yes its coming along nicely, just got started on it again the last week. I am going way overkill on it as I am testing out hardware that if it works out I will fit to the big lathe but this way is better as it keeps the big lathe intact and usable until I know for sure the new controller is working as it should,
Hood

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Re: Myford Super 7 - adding ball screws
« Reply #5 on: September 07, 2012, 02:05:13 PM »
I have done two lathe conversions. I did use a ballscrew on both machines. Actually I did the conversion on a 9" SouthBend with the ballscrew mounts that  I clamped onto the ways at the rear of the lathe. I removed all of the mechanisms at the front of the machine(apron?). It worked well until I acquired a Hardinge HLVH that was missing enough parts to make it useable as a cnc conversion only. I pulled the ballscrew from the SouthBend and adapted it for the Hardinge. The ballscrew is mounted on the rear of the Hardinge as well. I am using direct drive to the ballscrew using a 5 phase stepper. I have made a lot of parts with this machine. I am pretty sure that I only used existing threaded holes to mount the ballscrew. I don't like adding holes to machinery. The nut bracket bolts on where the taper attachment would have been fastened.
Re: Myford Super 7 - adding ball screws
« Reply #6 on: September 07, 2012, 03:13:09 PM »
Take a look at this thread for info on how to make a zero-backlash nut out of acetal for a standard lead screw.

I used these methods to make a nut for the cross slide on my Clausing 5914 and it worked really well. It would have been very hard to replace that nut with a ballscrew nut as the space is limiited, you'll seen pictures of the nut I made towards the end of the thread.

http://bbs.homeshopmachinist.net/threads/43645-Making-Acetal-leadscrew-nuts-the-easy-way?highlight=acetal

Paul T.
www.springtest.com
Re: Myford Super 7 - adding ball screws
« Reply #7 on: September 07, 2012, 04:44:38 PM »
Take a look at this thread for info on how to make a zero-backlash nut out of acetal for a standard lead screw.

I used these methods to make a nut for the cross slide on my Clausing 5914 and it worked really well. It would have been very hard to replace that nut with a ballscrew nut as the space is limiited, you'll seen pictures of the nut I made towards the end of the thread.

http://bbs.homeshopmachinist.net/threads/43645-Making-Acetal-leadscrew-nuts-the-easy-way?highlight=acetal

Paul T.
www.springtest.com


That's a slick way to make a zero nut. I saw this awhile back and was totally impressed. I made my cross slide out of delrin by using an Acme tap and under drilling the pilot hole a bit.  X axis holds plus or minus .001" so I am happy with that. I am going to try to tap my leadscrew nut, if its still too sloppy I will get the torch out and try the old melt a thread method. Nice work and ingenuity on such a simple method.

Regarding the ball screw, I would like to see just how mr. c did his SB. Now that he mentions it I can visualize a simple way to mount it. Unfortunately by taper attachment holds my X stepper motor lol
Re: Myford Super 7 - adding ball screws
« Reply #8 on: September 09, 2012, 09:48:48 AM »
Thanks to all.  Hood, I've had a couple of tries at buying a "Connect" CNC lathe on ebay that is ML10 based but the seller doesn't seem interested in realistic pricing.  This was a conversion that was sold as a CNC training lathe competing with Denford I think.  How are you protecting the leadscrew - is that a telescopic cover?

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Re: Myford Super 7 - adding ball screws
« Reply #9 on: September 09, 2012, 11:23:00 AM »
Yes the ballscrew is protected by telesopic tubes, they were standard on the Conect lathe.

These wee lathes go for crazy prices, suppose its because you can get them in a garden shed. Mine cost me as much as my big lathe did, £300, not sure if got it for a good price or not. Probably not as it was a Yorkshireman that sold it to me and they say a Yorkshireman is just a Scotsman except the generosity has been removed ;D

Hood