Surface finish

setting the gibs too tight can do this
building up stress then breaking free
i had this once because i didnt back off the saddle lock enough after using it
steve
 
The problem is found! The leadscrew is binding in the feed side bearing bracket. If I loosen the leadscrew bracket just a touch the problem goes away. The bearing fits the shaft fine when the bracket is not bolted tight to the bed. It appears that the bore of the bracket and the base of the bracket are not in the same plane. Now how to correct this? How would you hold the workpiece by the bore with it centered and machine the base flat to it?
 
Kevinb71 said:
The problem is found! The leadscrew is binding in the feed side bearing bracket. If I loosen the leadscrew bracket just a touch the problem goes away. The bearing fits the shaft fine when the bracket is not bolted tight to the bed. It appears that the bore of the bracket and the base of the bracket are not in the same plane. Now how to correct this? How would you hold the workpiece by the bore with it centered and machine the base flat to it?
Click to expand...

When you say the leadscrew bracket, are you referring to the bushed mount at the tailstock end? If so it sounds like you will need to shim this, perhaps a feeler gauge trimmed to fit beneath it of the proper size would work!

Good Luck,

NXr
 
did I miss something
what kind of lathe is this
a pick if you can may help
may be an adjustment
steve
 
Then,the problem was cyclic produced. Good that you found it out.
 
Kevinb71 said:
The problem is found! The leadscrew is binding in the feed side bearing bracket. If I loosen the leadscrew bracket just a touch the problem goes away. The bearing fits the shaft fine when the bracket is not bolted tight to the bed. It appears that the bore of the bracket and the base of the bracket are not in the same plane. Now how to correct this? How would you hold the workpiece by the bore with it centered and machine the base flat to it?
Click to expand...

I had a problem with the leadscrew on my 7x14 lathe binding up a while back. It wasn't casing the problems you are seeing; it was causing the lathe to either stall out, or the feed gear lever to disengage. I tracked it down to a bolt that secures the headstock side leadscrew bushing in place. It was drilled/tapped at a slight angle, so as you tightened it, it pulled the bushing out of alignment. The solution, add a washer between the bushing and the SHCS, then, slowly tighten checking the leadscrew friction.

I can now turn the leadscrew (half nut disengaged) with a single (oiled) finger. Makes a huge difference.
 
Hi Just a thought ,,,,,, is your lathe belt driven ? ,,,,,,, if so try adjusting up the belts , also check for any wear in the belts,pulleys , belt slip dose lead to poor finish.


Bob
 
Kevinb71 said:
The problem is found! The leadscrew is binding in the feed side bearing bracket. If I loosen the leadscrew bracket just a touch the problem goes away. The bearing fits the shaft fine when the bracket is not bolted tight to the bed. It appears that the bore of the bracket and the base of the bracket are not in the same plane. Now how to correct this? How would you hold the workpiece by the bore with it centered and machine the base flat to it?
Click to expand...

What about simply fabricating a shim to adjust the fit? I did this with the drive bar on my lathe (I have a drive bar for the carriage feed, and a leadscrew for threading).

John
 
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