Ballscrew conversion

[rodzilla]

For those of you who have converted an Rong Fu round column mill to cnc and ballscrews. Everything i have found on these ballscrew conversions so far points to 5/8 ballscrews but what i can't find is to what diameter do i turn the screws down to get the lock threads then step down to what diameter to fix the couplings to i am guessing that the screws were turned down to 1/2" for the lock nuts then turned down to 3/8" for coupling shaft to motor could someone lease verify my theory for me thankyou

[jhowelb]

On my mill I turned the screws to the diameter needed by the stock ball bearing thrust bearings. They were metric, but slightly larger that 1/2" in my case. Then I bored a timing belt pulley to fit the shaft. I marked the place where the shaft emerged from the pulley then turned the balance of the shaft form 1/8" shorter than my mark to the end to .490 and threaded it 1/2" X 13 so I could put a preload on the thrust bearings with a nut and lock nut then set the set screw on the pulley.

I hope I didn't lose anything in that diatribe. Make sense?

[acondit]

Originally Posted by jhowelb On my mill I turned the screws to the diameter needed by the stock ball bearing thrust bearings. They were metric, but slightly larger that 1/2" in my case. Then I bored a timing belt pulley to fit the shaft. I marked the place where the shaft emerged from the pulley then turned the balance of the shaft form 1/8" shorter than my mark to the end to .490 and threaded it 1/2" X 13 so I could put a preload on the thrust bearings with a nut and lock nut then set the set screw on the pulley. I hope I didn't lose anything in that diatribe. Make sense?

Here is a picture of the end I made for the ballscrew for my lathe. http://www.cnczone.com/forums/attach...6&d=1194578406

It is pretty much like John described.

There also was a recent article in either Home Shop Machinist or Digital Machinist by Roland Friestad of Cardinal Engineering that described making ballscrew ends for a Grizzly G1006 size mill (they are or used to be made by Rong Fu).

Alan

[rodzilla]

I think i understand you tunred the ballscrew till the threads were gone which i believe is .490 then put your pulley which was bored to the same diameter on and marked it then turned the shaft 1/8" passed the mark so the mark was gone and threaded it 1/2"-13 so that when you put the nut on you could tighten the pulley without a shoulder to rest the nut on then turned the rest of the shaft to what dimension i am assuming either 7/16" or 3/8" but you never stated which one and how does it work for you "do you have any thaughts as to if you were to do it again i would do this instead".

acondit do you know where i can get a copy of this article would you be able to scan it for me and email it to me?

[jhowelb]

The thrust bearings required a dimension a bit larger than half inch, say .580. Bored the pulley to .580. Lets say the bearings, races, housing and pulley require 1.5" and I had 3" of .580 shaft. I turned the last 1.6" down to .490 which is the size I needed for 1/2" thread. I threaded the .490 portion of the shaft. You might want to turn the end 1/2" or so th 3/8" or whatever your coupling is.

[rodzilla]

how can you turn the ballscrew down to .580 when the dimesions of the ball screw are .625 major dia. and .480 minor dia. unless you did not create a smooth wall on the turned screw but rather a partially turned down so a portion of the threads are still showing. I got this picture off of the roton website and they state .625 major and .480 minor. Could you please post a picture of what you are trying to explain so maybe i can wrap my head around this a little better (A picture is worth a 1000 words LOL!!!) thankyou for all of your help

[acondit]

Originally Posted by rodzilla acondit do you know where i can get a copy of this article would you be able to scan it for me and email it to me?

Rodzilla,

I looked up the article. The title is Computers in the Shop - CNCRetrofit for the Grizzly G1006 Benchtop Mill. It is in 3 parts in "Home Shop Machinist" in the March/April, May/June and July/August issues of 2007. You can contact Nancy Whitten <nancy at villagepress.com> for reprints or to find out about buying the three back issues. 1 (800) 773-7798.

Alan

[Spinnetti]

Although I was really chicken to dive into this, I did it 3-4 years ago and it was actually pretty easy. I didn't try to get clever, and it works great. Just need to make couple parts, mod a couple others. Bore out the ends for standard bearings, bore the pulleys to size, bore out the standard handles to fit back on to the handles (if you want to keep them), mod the screw nuts and make end adapters. The pics should answer several of your questions. Bear in mind that the screw is hardened. You ain't turning that unless you have better stuff than me. I just used a right angle grinder fixed to my lathe to get it to size. Worked surprisingly well.