Lathe carriage biting the bed

Suzuki4evr

Suzuki4evr

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Can someone give advice. I usually work near the chuck on my 1,5m lathe and ocasionaly do longer shafts in the 1m to 1,3m range. Now when I do do jobs like that I make sure to wipe the bed and anything that might have some grime buildup.I know the bed is more worn towards the chuck and less at the back,but what can be the reason or reasons for my carriage to bite down about halfway through the length of the bed and sometimes it doesn't,that part i don't understand. I went so far as to loosen the gibs completely,wich is just 2 pieces of flat bar that is tightened or loosend and locked with lock bolts. When I did that my carriage sits basically loose from the bed and still the carriage won't go further. The other day it completely locked up an did not want to go either way(I had to encourage it to move).I dont think the leadscrew or anything like that is bent. So Bill Gruby,Ulma docter,4GSR,Bill H,Tony Wells all you clever people(YOU KNOW YOU ARE). Please advise.

Michael
 
Curious! is this under feed? or hand feed? I'd look for something in the bed, or hanging from the back (where you can't see it) that's interfering with movement. Do you have a taper attachment?
 
I'm thinking a problem with the rack and pinion- have you looked under when binding occurs?
Mark
ps could also be binding up of the drive shaft with it's sliding component
 
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markba633csi said:
I'm thinking a problem with the rack and pinion- have you looked under when binding occurs?
Mark
ps could also be binding up of the sliding worm gear on the leadscrew due to wear
Click to expand...
I can't really see anything when binding. If it is the worm gear,why does it only happen when I am about half down the length of the bed and not the first half. I don't really want to strip the carriage for a few reasons. Firstly, I don't have the experience of that. Time is also a major issue because of my workload.
 
Can you effect a change in the binding by pushing/pulling on the leadscrew and the other control shafts when it happens? Also does oiling/greasing the shafts have any effect?
The problem is almost certainly in the apron, and unfortunately it may require some disassembly
Mark
 
Oiling does help,but not every time. I will check tomorrow by pushing/pulling the leadscrew if anything changes.
 
One thing that comes to mind is the feed rod and or lead screw, especially if the lead screw has a keyway cut in it.
All I can say is clean, clean, and clean, the lead screw, feed rod and remove the crud that builds up in the keyway. This could be binding in the unworn area of both if equipped with both, of if a single lead screw/feed rod. Likewise, the underside of the bed where the holdown gib bears against. Crud builds up on these surfaces and will cause the carriage to bind up and not move, even after loosening the gib.

If that don't help, let us know. Ken
 
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