What Am I Doing Wrong?

[taycat]

got pce of 4" rd offcut from local supplier for a project.
when i checked it found well out of square, set it up in 4 jaw so running true left it sat slightly away from back of jaw to set it true.
faced it off and still out of square yet when i put tool to edge of it and turn by hand it touches all way rd?
checked it using 3 different squares, in case one was out.

help before dent in wall from my head hitting wall gets much bigger please.

thanks

 

[JimDawson]

It sounds like you also need to take a cut on the OD to square it up. The other possibility is to make sure the piece OD is square to the chuck face before a taking facing cut.

 

[RJSakowski]

To square a piece of round, you will have to indicate the round close to the jaws and adjust for zero runout. Then move to the opposite side of the round and repeat, making adjustment with a soft face hammer. Go back to the jaws and repeat until you have zero runout at both ends. Note that round is most likely not round and you will have to turn it to true it. Once it is running true, you should be able to face it square to the cylinder axis. You may have a slightly concave or convex face if you have alignment problems but that is a different problem.
Because of the size of the piece, you may want to run between centers; at least use a tailstock center.
Note: if your lathe is turning a taper, you will never get it square but you can check that with a mike.

 

[randyc]

I'm sure you've already checked for this but if the carriage isn't locked when you face the work, cutting pressure will often deflect the tool away from the face as you traverse, resulting in out-of-square. (Also confirm that the chuck jaws are tight and the cutting tool is tight - more movement due to cutting pressure can result from either of these conditions.)