Good Ballscrew for 7x14 Lathe?
I used the Steele plans to turn a 7 x 14 into a CNC lathe. I quit fooling with it because the leadscrew was not accurate. It doesn't use a ballscrew. It uses a very expensive screw with a plastic nut from McMaster-Carr. I would like accuracy no worse than 0.005". I don't see how I can cut usable threads if it's less accurate than that.
I would like to give it another shot, with a real ballscrew, but I don't know of a good source for such a screw at a reasonable price. I don't want junk, but it doesn't have to be from Tiffany's, either. Can someone recommend a good vendor? Thanks for any help you can offer.
Re: Good Ballscrew for 7x14 Lathe?
I didn't realize this question was too hard to answer when I posted it.
Re: Good Ballscrew for 7x14 Lathe?
The Steele plans aren't public domain so it is a tough question.
Thomson and Roton have compact flange-less ball nuts compared to the common flange type from China.
Thomson has 3/8 diameter screws, possibly Roton as well.
Check their drawings to see if .anything fits ? Make your own flange.
.
Re: Good Ballscrew for 7x14 Lathe?
CNC Lathe
Here's my conversion using some thk ballscrews found on eBay
Re: Good Ballscrew for 7x14 Lathe?
The UK prices in this link are a bit of an eye opener but give an idea of how small these flangeless ballnuts get.
R12-04C1-RSW
I'm surprised you're getting such poor performance from acme screw and (assuming) anti-backlash nut..
The problem could be bearings in the fixed end support or the motor coupler ?
Re: Good Ballscrew for 7x14 Lathe?
Thanks for the link, Jfong. I have seen your project before. It looks like the left end of the lead screw is not supported. Is that correct? I was thinking it would be necessary to support the left end in order to apply rightward pressure on the screw and reduce longitudinal movement in the right-hand bearing. If you're getting good results without doing that, then I would rather do what you did and avoid the hassle of aligning two bearings and the nut.
Cyclestart, you are probably right. I had some wobble in the lead screw support and had to tighten it up.
Re: Good Ballscrew for 7x14 Lathe?
When I retrofitted Lathmaster 9"x30" mine I used a Hiwin from Taiwan, very high quality/precision for the price, double pre loaded nut, but the shaft was very hard and did not appear to be surface hardened, but hardened all the way through, I had to get a friend to turn in down with ceramic tooling.
At the time there was a guy on ebay that was bringing them in in the box full.
Lathemaster 9x30 First Chips!
Al.
Good Ballscrew for 7x14 Lathe?
The right bearing block takes up all the load. I believe there is two angular contact bearings in the THK support block. It came with a left side support with just a single radial bearing but I never installed it. The ballscrew doesn't spin very fast so it wasn't required to limit screw whipping. It wasn't meant to limit longitudal movement.
Re: Good Ballscrew for 7x14 Lathe?
It looks like there are a few Hiwin deals on Ebay. Also the linearmotionbearings2008 guy.
Re: Good Ballscrew for 7x14 Lathe?
what sizes ball screws are you using for your 7x14? z: 1605 500mm? x: 1204 25mm or 20mm?
Re: Good Ballscrew for 7x14 Lathe?
Hi,
to get that sort of accuracy you want a ground ballscrew. There is no such thing as a cheap ground ballscrew......rolled yes.....ground no.
overstock & surplus automation products: Motion Control, NSK Precision Ground & Rolled Ballscrews
Craig
