Replacement X-axis spindle FP-1

[DJ2]

Yes, if I really had to guess, I know the previous owner was a whizz at the lathe and maybe made a replacement nut for it. There are marks on the x-axis retaining nut indicating someone use a punch to get the lead screw out. So back in the day, both the bronze nut and lead screw must have been badly worn out (poor maintenance?), hence the machine being "put out to pasture". So he didn't machine another lead screw but the newer nut is now tight at the ends.

 

[thanvg]

Are you sure the tightness at the ends isn't due to gib adjustment?

 

[DJ2]

Thank you, I will check that out as well.

 

[ballen]

Hi Thanos,

Are you sure the tightness at the ends isn't due to gib adjustment?

I thought were were talking about backlash, not "hard" versus "easy" to move.

If the nut and lead screw are in good shape (no backlash) then easy in the middle and hard at the ends => worn gibs/ways.

If the backlash varies along the lead screw, this indicates varying wear in the lead screw. I thought that DJ2 is talking about this case: varying backlash along the lead screw, and 'tight' meant 'little backlash'.

Cheers,
Bruce

 

[DJ2]

Just to confirm the actual situation, as mentioned backlash worst case is about 0.040" (in the middle) and in this position the table movement is "easy". At the ends, backlash is about 0.015" and table movement is "stiff". This is an old machine and appears to have more than one issue, maybe all of the above gib/way wear, lead screw and nut! When I tram the table, there does not seem to be any excessive left to right x-axis 'deflection', am hoping the x-axis ways are in reasonable shape.

Thanks,
Dan

 

[AlfaGTA]

Repair the screw first to eliminate the variation between ends of travel and mid position...if the backlash is consistent over the total travel you can access the slide/gib wear.
Got to reduce the variables.

Cheers Ross

 

[thanvg]

Just to confirm the actual situation, as mentioned backlash worst case is about 0.040" (in the middle) and in this position the table movement is "easy". At the ends, backlash is about 0.015" and table movement is "stiff". This is an old machine and appears to have more than one issue, maybe all of the above gib/way wear, lead screw and nut! When I tram the table, there does not seem to be any excessive left to right x-axis 'deflection', am hoping the x-axis ways are in reasonable shape.

Thanks,
Dan

If there is backlash even at the travel ends then, I guess, the screw is not the one to make the motion stiff (unless something was done very incorrectly in the past).
In any ways, as Ross suggested, try to reduce the variables: since you're accessing the screw/nut subsystem, loosen the gib or remove it completely to take it out of the equation.

BR,
Thanos