Chris's Pm1236

[petertha]

Is the carriage clamping mechanism on your PM lathe similar to this? (my lathe). Was the topside originally a nut? Just curious, my (hex nut) requires a bit of futzing sometimes to get the tightening initiated. Sometimes the lower clamp will just rotate with the tightening motion. Seems like it needs just bit of lateral force on the nut simultaneous to tightening, or if the carriage is displaced just a bit & then it 'engages'. The pic shows it has some sort of eccentric shape on the shoe. I haven't removed it. but suspect the issue is in there somewhere. Bu maybe your handle mod, once set up, limits the clock rotation to a narrower angle to either 'free' or 'clamp'?

 

[petertha]

Yes the quill had rotational slop.

Interesting. Reason I asked: my tailstock el-cheapo DRO woody mock-up - I was concerned that hard mounting the plate & vernier to the quill might bugger up the vernier if it sees any twisting motion. I also have a bit of rotational slop like when a drill bit engages the material. So I've been testing this assembly with kind of a convoluted slider pin concept in the quill plate to allow for rotation. You've inspired me to investigate & eliminate rotation, its likely the same issue.

 

[1cjk]

Is the carriage clamping mechanism on your PM lathe similar to this? (my lathe). Was the topside originally a nut? Just curious, my (hex nut) requires a bit of futzing sometimes to get the tightening initiated. Sometimes the lower clamp will just rotate with the tightening motion. Seems like it needs just bit of lateral force on the nut simultaneous to tightening, or if the carriage is displaced just a bit & then it 'engages'. The pic shows it has some sort of eccentric shape on the shoe. I haven't removed it. but suspect the issue is in there somewhere. Bu maybe your handle mod, once set up, limits the clock rotation to a narrower angle to either 'free' or 'clamp'?

View attachment 124465

No mine has the bolt going through to some sort of threaded plate. I just pulled the bolt out and matched the size
lever to the bolt. McMaster carries a nut version.
http://www.mcmaster.com/#control-handles/=11hyydy

 

[1cjk]

Interesting. Reason I asked: my tailstock el-cheapo DRO woody mock-up - I was concerned that hard mounting the plate & vernier to the quill might bugger up the vernier if it sees any twisting motion. I also have a bit of rotational slop like when a drill bit engages the material. So I've been testing this assembly with kind of a convoluted slider pin concept in the quill plate to allow for rotation. You've inspired me to investigate & eliminate rotation, its likely the same issue.

View attachment 124466

That is the reason I replaced mine. There was to much twist to mount the scale with out it moving and binding up. I milled the sides of the new pin about .001-.002 wider than honed it down on a stone for a perfect fit. There was also a little burr in the key way and I took 1000 grit paper folded to fit and smoothed any high spots in the key way. Now it's silky smooth and zero slop.

 

[Guv]

Well done!!