Turning Problem

[v-twindad]

Hello all,

Im trying to turn a motorcycle steering neck down and my problem is when I try to make the finish cut with my power feed Im getting some really funky grooving action, not just real fine grooves but pretty deep ones. Somewhere I heard that if the cutter is above the centerline that it will cause this, can anyone verify that for me or maybe give me some other possible causes. All my slides are adjusted with no slop so I dont think that is the problem, and I have the gear train set at the highest TPI (256) and I am turning it at a pretty high RPM. ANY IDEAS?

Thanks
Chuck

[norm]

set the cutter at the center line height

and run the proper rpm
with a sharp cutter

adjust the feed rate to suit

[captainkirk]

As stated set cutter to center (or slightly below) it sounds like your tearing the metal as opposed to cutting it. There are a number of reasons for tearing,Tool is dull, incorrect feed and speed, incorrect cutting depth (to little is worse than to much in most cases) incorrect cutting fluid, material with hard inclusions.
First I would sharpen the tooling, I would take a cut of between .005 to .010 (total decrease in diameter between .010 and .020) cut no less than .003 in most cases. Use the correct cutting fluid for the material
All this advise is based on the assumption of a rigid lathe in the 10" to 13"range if its a very small lathe that lacks rigidity it might be related to chatter. It is a guess as to the cause without much more information.
If you can't figure out the cause measure the diameter across the high parts of the grooves then smooth it with a file and remeasure the diameter use the difference figure obtained to estimate how much to leave on the shaft so that it can be cleaned with a file to fit the bearing races.