Lathe Cross Slide Problem

[EdK]

(07-04-2014, 09:05 AM)Sunset Machine Wrote: That sounds like the same complaint you made in post #1. Have you checked to see that the leadscrew is parallel to the slideway?

One of the many complaints.

That's a good point about the lead screw being parallel to the slides. I'm not sure how I could measure it though.

Ed

[EdK]

Well I'll be damned. Success at last.

I met a friend at the Minnesota Landscape Arboretum this morning for a session of picture taking and when I got home I was kind of dreading having to make yet another shim for the nut. Realizing it won't fix itself, I decided to have at it. I pulled out the next size up of my stash of brass shim stock, .015", and was about ready to cut a piece off to make the shim when I decided to try the .031", .008" and the .012" shims together and see what would happen. To my utter amazement, it worked like a dream. No binding or scraping the full travel length. Nice and smooth all of the way. At this point, I hadn't installed the gib yet. I was just pushing against the side to keep it against the dovetail while I cranked the hand wheel. So I put the gib in expecting the worst and low and behold it works like a charm. I measured the backlash and it's about .0015". I walked over to my work bench to get some allen wrenches and spotted a shim sitting there. I and wondered where the hell it came from and suddenly realized it was the .031" shim. In reality I had only installed the ,008" and the .012" shims, not all three of them.

All I can say is it's a damned good thing I don't do this for a living.

I just need to reinstall the DRO scale and this project will finally be done.

I have to thank Ken again for being so generous with his time and materials. I would have never gotten this problem fixed without his help.

Time to celebrate.

Ed

[DaveH]

Well done
Persistence paid off.

DaveH

[Mayhem]

Well done Ed!

Perhaps you should do this for a living - if you charged by the hour, you would make a killing

[EdK]

(07-04-2014, 06:30 PM)Mayhem Wrote: ...

Perhaps you should do this for a living - if you charged by the hour, you would make a killing

[PixMan]

I'm so glad you got it to this point Ed! Did you accidentally add an extra zero there with the 0.0015" backlash amount? Wow.

Best of luck with the "final assembly", and be sure to apply lubrication liberally as you do it.

[EdK]

(07-05-2014, 05:36 AM)PixMan Wrote: I'm so glad you got it to this point Ed! Did you accidentally add an extra zero there with the 0.0015" backlash amount? Wow.

Best of luck with the "final assembly", and be sure to apply lubrication liberally as you do it.

Thanks Ken.

No added zeros, .0015" it is. I measured it multiple times and got the same result.

I'm going to do some testing of the power feed to make sure that works and then reinstall the DRO scale, if I can find it.

I decided to measure the travel per revolution of the hand crank just to see how it compared to the original lead screw and I consistently got .099". That's exactly the same as I was getting with the original lead screw. I'm assuming the diameter of the hand crank dial must be off a tad since I should be getting .100" of travel per revolution. How would I calculate what the diameter should be to make a new dial to eliminate that error?

Ed

[PixMan]

The diameter shouldn't matter. If the dial has .200" worth of graduations and you are coming around to the same line for one revolution, it should travel .100" per turn because it's a 5/8-10 LH Acme thread.

If you only get .099", then my lathe's gearing must be off by 1%. Nuts. That frustrates me as there's really no way to fix your screw nor my lathe.

[EdK]

(07-05-2014, 09:03 AM)PixMan Wrote: The diameter shouldn't matter. If the dial has .200" worth of graduations and you are coming around to the same line for one revolution, it should travel .100" per turn because it's a 5/8-10 LH Acme thread.

If you only get .099", then my lathe's gearing must be off by 1%. Nuts. That frustrates me as there's really no way to fix your screw nor my lathe.

Ken,

The dial has .100" worth of graduations. Good point about the diameter. I thought about it and realized as long as the dial is marked properly then the diameter shouldn't matter.

It's not a big deal since I have the DRO. I think I'll try remeasuring with a couple of different dial indicators and see if I get the same reading. Once I have the DRO scale reinstalled I can check it with that also.

Ed

[PixMan]

So you have one of those dials I hate, the ones that take off TWICE the amount dialed in? Good reason to have DRO!