another lathe question

bfullmer

Member
Trying to turn down a king pin from a big truck and the whole tool post assembly started moving up and down on the ways what am I doing wrong ?? Anyone in central mich that would give lathe lessons?? No local schools around here .
 
The cutting edge of your tool must be on center. If it is below center, you will have it doing some bad things. Above center and it will not cut. With the lathe spindle stopped move the cutting tool up close to the work piece. Hold something small and thin between the tool and the work piece. If the tool is on center, the piece will be straight up and down. Adjust cutting height until it is straight.
SDE
 
Both above posts (especially checking your tool for center--much below center can really be asking for trouble), plus two other things to check--taking too much of a cut and whether your carriage is extended too far. As a rule, you want your carriage back as far as practical--too far out will create a lever action when you start cutting and pull the entire thing down, causing chatter or worse. Does your machine have adjustable gibs? They might also be loose or poorly adjusted, which can also cause this, or at least make it worse.
 
(quoted from post at 15:46:34 11/07/14) The cutting edge of your tool must be on center. If it is below center, you will have it doing some bad things. Above center and it will not cut. With the lathe spindle stopped move the cutting tool up close to the work piece. Hold something small and thin between the tool and the work piece. If the tool is on center, the piece will be straight up and down. Adjust cutting height until it is straight.
SDE

I was taught to have the cutting tool just slightly BELOW center, and that is how I always do it. Directly on center will cause chatter and result in a rough cut.
 
[b:8b25005d97]I was taught to have the cutting tool just slightly BELOW center, and that is how I always do it. Directly on center will cause chatter and result in a rough cut.[/b:8b25005d97]

As a retired Tool&Die Maker---I agree!
 
(quoted from post at 18:01:45 11/08/14) [b:4817d41534]I was taught to have the cutting tool just slightly BELOW center, and that is how I always do it. Directly on center will cause chatter and result in a rough cut.[/b:4817d41534]

As a retired Tool&Die Maker---I agree!

Thank you. I was a tool maker.
 
Are you sure the stock/king pin is turning down onto the cutter? (the correct direction)?
 
I did that too... center your kingpin to the cutting tool ... there are lots of YouTube videos showing how...
BUT NOW THAT YOU HAVE DONE THAT. you will need to check the gibb alignments on your lathe...
it did not take much to knock my gibb out of alignment...

the kingpin is very hard, molly, it can be cut but it will not look as good as factory ones, they grind them to spec
 
Yes, that is what I had to do was tighten up the gibb on the compound slide several times until I got it tight without dragging.
 

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