When I restored my 1944 vintage Logan 820, I was also concerned about the play in the cross-slide and compound lead screws/nuts. I investigated replacement but other than purchasing Acme threading tools (internal and external), did not take any action.
Joe: When I had it torn down, I did take measurements and make sketches, here are the specifications you asked about.
- Cross-slide leadscrew: 7/16"-10 tpi left hand Acme thread
- Compound leadscrew: 3/8"-10 tpi left hand Acme thread
I searched for vendors selling Acme threaded rod to meet these sizes, but found nothing. To get off-the-shelf 10 TPI Acme rod, it looks like you need to go up to 1/2". I did some less than rigorous investigation and think it might well be possible to fit a 1/2" screw and nut into the standard Logan slide. Anybody comment on this? I don't think the compound slide would tolerate the 1/2" leadscrew.
As to whether the slop is in the screw or the nut, here's what I just measured on my 820: (Measurements taken with the screws almost fully CCW (outwards from spindle), mid range, and nearly fully CW (inward). Measurements all in thousandths of inch.
CCW Mid CW
Compound slide: 7 7 6
Cross slide 87 4 3
*Some of this slop is shaft endplay, but I conclude the cross-slide screw is badly worn (as expected) out where one would be turning fairly large diameter stock. I suspect previous owners may have replaced the nuts.
If I could get the proper Acme rod, I'd consider making a new cross slide shaft. Barring that, there's always making your own. I just love being able to use my lathe (and mill) to make its own parts. It's on my list, but low-priority for now.
Based on the success I had in quickly, easily making a 5/16-32 UNEF tap, I'd try making the Acme tap from drill rod before buying an expensive one.
Greg
I took your post and went to my shop and measured the movement i have....I was waaaaaaay of the actual distance .012-.018 was i just seemed like a whole lot to me,( remember I am a neophyte Hobby machinist) sort of like having a grain of sand in your mouth....feels like a stone!
I tried your suggustion and it did help...but did not aleviate the problem.
i have looked at the nut and it does not look good indide the nut. Probably where most slop is coming from. screw look clean but neeed to be properly checked out.
there is a replacement nut for sale, on e-bay, New Manufacture and it is $48.00+/- plus $5.00 shipping. it looks easy enough to make until I looked at the price of taps for acme thread ( $ 60.00-70.00 ???)
I don't know the exact dimensions of the screw thread but appears to be 3/8'-1/2 "diameter. hopefully someone can give me the exact size and pitch. As you can tell I havn't looked DEEPLY into this matter
After 9 months of taking this beautiful lathe down to it's shadow and refurbishing it bolt by bolt I and expect to throw the switch and see it run within a week.. then i can start tweaking it.
Joe
