finally got started on my X3 conversion. whipped up a bracket to mount my angle grinder on the cross slide of my 7x10 to grind the ballscrew ends. works good to get at least close to final size. I think I'll stop short and use conventional bits to get to final size. Here is a quick trial on one end with only the grinder.

http://img57.imageshack.us/img57/9827/ballscrewgrindingfixturpy7.th.jpg (http://img57.imageshack.us/my.php?image=ballscrewgrindingfixturpy7.jpg)
http://img143.imageshack.us/img143/2144/ballscrewgrindingfixturca2.th.jpg (http://img143.imageshack.us/my.php?image=ballscrewgrindingfixturca2.jpg) http://img442.imageshack.us/img442/8238/groundend2js5.th.jpg (http://img442.imageshack.us/my.php?image=groundend2js5.jpg)

I just did the same on my roton ballscrews for my clausing 8520 project. I found these screws really kicked my *ss as far as using carbide tooling - my tired old south bend just didn't seem rigid enough.

I ended up grinding to final size. I first tried an angle grinder like you, then switched to a bench grinder and that seemed to give me a better finish. My angle grinder had a very crappy wheel on it though.

Anyway best of luck, I found this ballscrew machining to be a pain-in-the-arse job that was a relief to have finally finished.

- John (in Algonquin)

Awww, that's such a cute little lathe...

That's very interesting. I am going to do the same but I thought you need a proper grinder fixed to the lathe to do the job. Do you have more photos showing how you attached the grinder? I have a C3 lathe which is bigger and I am sure I can do the same as you did.

How did you make sure the jaws of the chuck don't bite into the ballscrew?

How fast are you spinning the ballscrew to avoid it from vibrating?

Any advice on how you thread the end will be great. Will bookmark this page.

Alex

alexccmeister,
When I did mine, I used a die grinder and made a bracket to hold it on the compound. The bracket was a piece of angle Iron and end brackets were simple clamp blocks. I used this to get through the hard stuff and then normal tooling to finish and thread as necessary. The wheel used in the end was as shown and seemed to work the best was the common "lawn mower blade sharpener" as shown.

Bubba,

Thanks for the info. Thats an extra idea at my finger's tip. Wonderful.

BTW, how fast did you turn your ballscrew while grinding?

Alex

Holy smokes Bubba. What rev's was the die grinder doing? Those die grinders go over 20,000rpm. Let CNCZone viewers be warned!!!! Most small grinding wheels like that will not tolerate speeds like that and someone will get badly hurt!!!!!

Those wheels are meant for pistol drills...... Much slower.

Chich

As I remember, I was turning the ballscrew in back gear ~100 rpm.
Forgot to mention, that I throttled the speed of the grinder down with a simple valve on the air line.

I was careful and kept the speed down and took real light cuts. Also, the grinder was angled slightly off the Z axis of the lathe to the grinder would clear the ball screw when I was cutting closer to the headstock. Also, used a center in the ballscrew and took real light cuts. Took a while, but was worth it. The Craftsman/Atlas was not rigid enough to cut the hard stuff even with a carbide tool.

That's very interesting. I am going to do the same but I thought you need a proper grinder fixed to the lathe to do the job. Do you have more photos showing how you attached the grinder? I have a C3 lathe which is bigger and I am sure I can do the same as you did.

How did you make sure the jaws of the chuck don't bite into the ballscrew?

How fast are you spinning the ballscrew to avoid it from vibrating?

Any advice on how you thread the end will be great. Will bookmark this page.

Alex

Hi Alex...making a mount for this grinder was easy. I just used a piece of angle, and used the original holes for the finger guard. I have other grinders that would have required more work to get to fit. Sometimes you just get lucky I guess. I just removed the tool post and mounted the bracket to the tool post stud hole.

A piece of conduit slit lengthwise was a perfect fit to cushion the screw from the jaws. This was just a quick test cut, but when I do the real thing I'll be using the live center to support the end of the screw. I just turned it at the slowest speed of the lathe, about 200RPM.

I just used a cheap 1/8 thick cutoff wheel and took really light cuts. It goes quick though. The wheel does wear some though, so the diameter was not as consistant as it should be, even for that short distance. That is why I am just going to get close, then use conventional tooling to get the final dimensions. I'm going to see if I can find a proper pink or white grinding wheel that will fit the grinder and see if that is any better.

I was going to just use a die to cut tthe threads, or possibly try doing it with the lathe. I just haven't had much practice cutting threads yet.

http://img232.imageshack.us/img232/6195/grindermount2id3.th.jpg (http://img232.imageshack.us/my.php?image=grindermount2id3.jpg)

A few things to add here.

First - most air motor tools have a quasi speed regulator under the lever valve. Look on the side opposite the lever and you will see a brass screw. This is a ball valve and limits the volume rather than the pressure so your motor will still have some power at lower speeds.

Second -if you are grinding on your lathe, cover up the ways. When you are done, clean the crap out of everything - the dust is lapping compound and will destroy your pretty ways.

Third - dressing the wheel: Dressing by hand for any degree of precision is not likely. I am not saying it won't work, I am just suggesting that you fashion a rigid way to dress the wheel in place. Rigidly mount a single point diamond dresser and run the wheel across it until you have a smooth, chatter free, flat wheel. Dress in the same plane as you are grinding - meaning that in this case you are using the front edge of the wheel, so dress from the front to create a flat and straight wheel. I have mounted the dresser to a steady rest that was positioned so that I could get to it without destroying my set up. This way the wheel could be trued up for a finish kiss on the part. The results of a perfectly dressed wheel are quite profound provided that it is balanced. That's another story.

Scott