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What's wrong with my lathe?

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harrzack

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#1
Greets! I have a LMS 3536/Sieg C4 lathe that for the most part is doing ok - especially after I REALLY learned to tighten things up GOOD.

Now I see an odd issue - when I do a power feed cut on the diameter, I'm getting a good finish. When I stop and hand-crank the carriage back out - there is a rather heavy cut being done again - seems a bit more than just spring. What might be causing the movement when hand moving the carriage as opposed to power feed?
 

JimDawson

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#2
That is spring. If everything is tight then hand cranking in either direction is the same as feeding under power. Play with the tool height, angle, and make sure the tool is sharp and not cutting behind the tip.

To test this theory, take a cut at a known depth, back the cross slide out, measure the part. My guess is that it will be larger than what you dialed in.
 

Mitch Alsup

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#3
You need to get both hands coordinated so that you can take the carriage out of movement and back out the cross slide in a single movement.
 

JimDawson

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#4
You need to get both hands coordinated so that you can take the carriage out of movement and back out the cross slide in a single movement.
Good advice for threading, but not applicable in this case.
 

David S

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#5
Also check the gibs for the cross slide. It sounds like the cross slide being driven in, is perhaps deflection toward the tailstock and then it relaxes toward the headstock as you manually retract it.

David
 

MrWhoopee

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#6
Back the tool out, return the carriage, crank the cross-slide back in to the same setting as the first pass. Take another pass with power feed. What happens?
 

higgite

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#7
What material are you turning? What diameter? How much overhang/stick out from chuck? With or without tailstock center?

Tom
 
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