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Author Topic: CNC watch lathe  (Read 14700 times)

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Offline Tweakie.CNC

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Re: CNC watch lathe
« Reply #10 on: March 10, 2009, 10:10:56 AM »
Nice work Vince.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline RICH

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Re: CNC watch lathe
« Reply #11 on: March 10, 2009, 05:30:48 PM »
Viince,
Was the bed hardened?
How's the elbow's feel after doing the scraping?  ;)
RICH

Offline N4NV

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Re: CNC watch lathe
« Reply #12 on: March 10, 2009, 06:22:24 PM »
I do not believe the bed was hardened.  The Biax scraper I was using is electric.  http://www.dapra.com/biax/scrapers/
I learned how to scrape by reading the Connelly book and re-scraping a Southbend lathe.  That was all done by hand with a carbide scraper. 

Vince

Offline N4NV

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Re: CNC watch lathe
« Reply #13 on: March 10, 2009, 10:27:43 PM »
I found some anti-backlash nuts on the web that have the same 1/4-20 acme thread as my screws.  The manufacturer claims they are backlash free up to 6 pounds.  Since I will be operating in the oz range, they should work fine.  In the picture they are the red part, the round disk is the mounting flange that I will have to machine smaller to fit.

Vince

Offline RICH

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Re: CNC watch lathe
« Reply #14 on: March 11, 2009, 06:41:30 AM »
Vince,
Should work for what your doing and time will tell. Remember that another source of backlash will be
at the bearing so take a look at how Sherline does their screw to motor mounting. Just a few thoughts.
RICH

Offline N4NV

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Re: CNC watch lathe
« Reply #15 on: March 11, 2009, 10:31:21 AM »
With the loads so light and the travel so small, I am not going to use a bearing.  The lead screw will attach directly to the stepper motor.  The stepper motor has a thrust washer installed and my test shows it takes 5.2 pounds to get this washer to deflect and as a result cause backlash.  So at the few ounces of thrust I will be using the lathe should stay zero backlash.

Vince

Offline N4NV

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Re: CNC watch lathe
« Reply #16 on: March 23, 2009, 02:43:17 PM »
I have been busy with other projects. I just about finished my Miser stirling engine. You can see that here:

http://www.youtube.com/watch?v=vdBYzzhe_To

I laid out, drilled and tapped the holes in the lathe bed for the Z axis linear rail. I made lots of measurements with my Mill prior to drilling the bed and found that it was straight and parallel to at least .0005" (my mill has about .0002" repeatability). After drilling and tapping the holes I put the bed back on my surface plate and marked it with high spot to check to see if any of the holes pulled up some high areas. I had to do a little touch up scraping around three of the holes, but other than that it stayed flat to at least .0001".

I have to find some special metric screws to proceed so I can attached the cross slide to the "trucks".

Vince

Offline budman68

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Re: CNC watch lathe
« Reply #17 on: March 23, 2009, 03:58:56 PM »
Pretty nifty, Vince, did you dust this on a grinder to get it within a tenth?

Thanks,
Dave
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Offline N4NV

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Re: CNC watch lathe
« Reply #18 on: March 23, 2009, 04:11:28 PM »
Pretty nifty, Vince, did you dust this on a grinder to get it within a tenth?

Thanks,
Dave

A grinder is not accurate enough.  I hand scraped it and used a surface plate that was good to .00005".  You can see part of the process at this thread:
http://www.cnczone.com/forums/showthread.php?p=587073#post587073

Vince

Offline budman68

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Re: CNC watch lathe
« Reply #19 on: March 23, 2009, 04:20:19 PM »
??? a grinder is not accurate enough?

Um, ok, I'll just say you're doing a great job and stay out of this one -  ;)

Thanks,
Dave
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Just because I'm a Global Moderator, don't assume that I know anything !

Dave->    ;)