Advice on a Compound Lead Screw

tjb

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Hello to All.

Some of you may remember that I've recently posted some ?'s about a Jet P1024 look-alike that I have (Kin Shin Model KS3.5FK) and received some invaluable information from many of you. The machine now runs great and is wired properly. Thanks again.

I have what appears to be the final (hopefully) issue on this machine. The compound lead screw is very slightly bent. It's too slight to tell with the naked eye unless you know it's there, but it's bad enough to where I can only get about 90 degrees turn before it starts binding. Since I plan to use this machine primarily for threading, that's obviously not acceptable. If I remember correctly when I first started going through this machine, Ulma Doctor (Mike) suggested trying to straighten it. Mike also sent me the manual for Grizzly's G9249 lathe, which lists a similar 'looking' part for the compound lead screw: pp 75 and 76 of the manual, Reference #453, Part #P9249453, 'Cross Slide Leadscrew M15'.

Here are my challenges.
1. I'm assuming that that is the right part for the compound lead screw. Can anyone confirm if this is right or wrong?

2. I called Tech Support at Grizzly, but they can't give me actual spec's on that part to see if it matches mine. Obviously, if it won't cross over without more than moderate modifications, it won't work. Does anyone have experience with the Grizzly part and its potential crossover with a Jet P1024? It's only about $40, so it's not cost prohibitive if I have to buy it, but it's a complete waste if it doesn't fit.

3. How big a deal is it to straighten mine? Mike, you gave me some info on how to do it, but I'd prefer not to even try it until I know the status on availability for a replacement.

4. Anybody know of any other resource for buying one of these?

As always, thanks to the knowledgeable and helpful community of Hobby Machinist.

Regards,
Terry
 

RandyM

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Hey Terry,

Personally, I'd not be hesitant in trying to fix your part, even if you are uncomfortable doing it. Here is the way I view it. The part is no longer usable (by your determination), so the existing part has no value and hence you can not do any further damage by making the attempt. Use a straight edge or surface plate to gage your progress. Use a hydraulic press or vise to slowly push it back into shape. You'll need to be patient and go slow and steady. Once you get to where it all is looking good, install it and test it out. You have nothing to lose, anyway you look at it, if you fail you are still in search of a replacement part. If you succeed, you'll save yourself the agony. Good luck.
 
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Bill Gruby

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It has been my experience that most Grizzly parts do not interchange with Jet. I tried in vain with my 9x20. Gears don't mesh correctly etc. I finally ended up making most replacements myself. Jet prices were too high in my opinion. If you need the lead screw and want to cross buy you need to buy the nut and everything else that corresponds with it.

"Billy G"
 
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mikey

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I would try to straighten it. If you prefer not to do that and cannot find an exact replacement then just make one from Acme threaded stock. If your nut is not excessively worn, this will result in a complete fix. If the nut is worn then you'll need to make the nut, too.
 

tjb

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Hey Terry,

Personally, I'd not be hesitant in trying to fix your part, even if you are uncomfortable doing it. Here is the way I view it. The part is no longer usable (by your determination), so the existing part has no value and hence you can not do any further damage by making the attempt. Use a straight edge or surface plate to gage your progress. Use a hydraulic press or vise to slowly push it back into shape. You'll need to be patient and go slow and steady. Once you get to where it all is looking good, install it and test it out. You have nothing to lose, anyway you look at it, if you fail you are still in search of a replacement part. If you succeed, you'll save yourself the agony. Good luck.

Yeah, Randy. I'm not too uncomfortable in trying to straighten it. Just thought I'd see if it was easy and relatively inexpensive to buy one. Then I'd stick the old one in a scrap bin for a future who-knows-what project. I suspect I'll end up trying to fix this one. My shop press is pneumatic, and I've never tried to do anything quite this precise with it. I'm concerned that I won't have enough control on the foot pedal to not 'overcorrect'. I have a good heavy duty vise, so that might be a better way to go. What do you think?

Regards
 

RandyM

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Yeah, Randy. I'm not too uncomfortable in trying to straighten it. Just thought I'd see if it was easy and relatively inexpensive to buy one. Then I'd stick the old one in a scrap bin for a future who-knows-what project. I suspect I'll end up trying to fix this one. My shop press is pneumatic, and I've never tried to do anything quite this precise with it. I'm concerned that I won't have enough control on the foot pedal to not 'overcorrect'. I have a good heavy duty vise, so that might be a better way to go. What do you think?

Regards


Sounds like a flawless plan. Let us know how you fair.

P.S. If you still want to use the press and are concerned about over doing it, then I'd make a fixture with adjustable stops.
 

tjb

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It has been my experience that most Grizzly parts do not interchange with Jet. I tried in vain with my 9x20. Gears don't mesh correctly etc. I finally ended up making most replacements myself. Jet prices were too high in my opinion. If you need the lead screw and want to cross buy you need to buy the nut and everything else that corresponds with it.

"Billy G"
Thanks, Bill. That's exactly the kind of information I need to know. I don't have the measurements in front of me right now, but I think my leadscrew is 5 and 15/16 inches long, Acme 8 TPI, and 20 TPI for retainer ring on the hand dial end. It appears to have started with 5/8 stock but only about 1/8 inch is still that diameter (and that is about 2 inches from hand dial end). On both the leadscrew side and dial side, it is milled down. I suppose if the overall length is tolerable, I could buy (or make) the nut as well, and machine to fit for the dials as necessary. (Here's an APB for anyone who might know the overall length/major diameter of the Grizzly leadscrew.)

What do you think? (Comments from anyone else appreciated as well.)

Regards,
Terry
 

tjb

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Make a new one. You got the original to copy.
Thanks, Mark. That's going to be my option of LAST resort. From what I've read and heard, I suspect I need a lot more practice before cutting Acme threads.

Regards
 

tjb

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I would try to straighten it. If you prefer not to do that and cannot find an exact replacement then just make one from Acme threaded stock. If your nut is not excessively worn, this will result in a complete fix. If the nut is worn then you'll need to make the nut, too.

Mikey,

The nut's in pretty good shape, so that's the same knee-jerk option I had. (I did that on an older Harrison lathe, and it worked out great.) There's an added challenge here, however, because the overall diameter of the leadscrew is 5/8 inch, but it's milled down on both ends of about a 1/8 inch section (see my response to Bill Gruby's post above). If I end up doing it that way, I'll probably start with a slimmer piece of Acme threaded rod and build up a shoulder. Shouldn't be too difficult, but I'd still like to find one if it's out there.

Thanks for the response.

Regards,
Terry
 
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