1. Home
  2. ⏣ General Metalworking
  3. Lathe cross feed screw finally gettin bad enough to replace

Lathe cross feed screw finally gettin bad enough to replace

I have an old taiwan made 14 x 40 lathe (late 70's vintage, TWS brand) which was already pretty beat when I aquired it (free!)

For the most part, things work well and it can maintain tolerable accuracy for what I do so I would like to replace the one part that brings it down: The cross feed screw. This screw is fairly typical in style, several steps, each with different threads journals and keys for the handles, bearings and such with a bronze nut on the under side of the cross slide. Bronze nut is split with a wedge that adjusts via a set screw to take up backlash. The wear in the middle is such that taking up backlash there makes it tight at the ends of movement. Also, the arrangement is constantly loosening.

So..here's the question. I know that I can't find an exact replacement and need to scab together a new system. I can go high end and use a ball screw, or lower end using something similar to what exists or somewhere in between. My guess is that the designs haven't changed much so I might be able to find a similar screw that could be modified from the Grizzly or Jet parts depts.

Any suggestions on the best bet in the long run (other than buying some better iron)? I hate to open a can of worms and turn this into a nightmare project but it really needs to get done soon.

Thanks,

Koz

Reply to
Koz
Loading thread data ...

From what I've seen, ball screws are far more aggressive TPI, and unsuitable for manual work - in that I wouldn't use it, but you're not me.

There was an article in HSM or PIM covering the use of moglice - a kind of an epoxy with embedded material for repair of a lathe lead screw. This approach would allow you to use your existing lead screw.

Some of your friction would be expected to be also from the worn ways of the cross slide, so merely replacing the lead screw does not guarantee elimination of binding.

Koz said the following on 7/28/2005 11:13 AM:

Reply to
John Hofstad-Parkhill

I had a worn out cross-feed lead screw on a 1962 Colchester Triumph. There's no problem getting lead screws material, just matching the end with the bushing and pinion.

I bought a new length of lead screw and and a new bronze nut. The nut had to be machined to fit, but they're supplied oversize for this.

I cut off the old section of thread and kept the section throught the bushing and the pinion. Throught this I bored and reamed a hole on center. I machined the end of the new lead screw section with a matching diameter. The fit was reasonably tight, but I put a split pin in just to make sure.

Bruce

Reply to
sawdoc

Ballscrews will turn if pushed on the end. So this means that if the tool wants to dig in it can cause the ballscrew to turn which lets the tool dig in even more. You may also have a hard time finding a ballscrew with a pitch as fine as you current leadscrew. Acme thread is best in this application. ERS

Reply to
Eric R Snow

My fathe rin law has a Taiwanese late, of similar size and age. The lead screws appear to be made from free machining steel, so wore out quickly. A few years ago, I got a length of 4140 ground leadscrew from MSC in th eright pitch (and left hand). He cut off the worn one and welded or pinned on a piece of the new one. They also had the nuts, which would have had to be made to fit under the cross slide, but in his case, the bew screw and a bit of adjustment made it ok. I expect it to last for a long, long time It was around $US100 for a 3' length Geoff

Reply to
Geoff M

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.