Trying to improve parting

Got it....
 
One thing that I consider with parting is tool geometry. A parting tool has a rake and a clearance angle, and your setup in the lathe will determine the presentation angle. Some tool holders hold a parting tool dead level, and some are angled up pretty far. Try to visualize how the rake angle changes as the presentation angle changes. By ignoring the effect of the tool holder's angle, you could end up with a very bad virtual rake angle depending what tool holder you have. To set the presentation angle (and thus the virtual rake angle) correct, I grind parting tools in the tool holder.
 
Good thought on, in the holder, I'm at 7* on the flat plane holder.
 
7 degrees, with the tool held horizontal, is actually a very good relief angle for a parting tool.
 
a parted surface quite often looks like azz and isn't necessarily flat. I've learned to leave 0.5-1mm extra on the piece I'm parting off so I can flip it round and face it. Usually need to do that anyway to break any burr raised by the parting tool or get rid of the little nub when the piece breaks off.
 
Joe Piezinski has a good video on parting. Mikey mentions that lots of variables are at play. He didn’t mention phases of the moon, but I’m not convinced it isn’t one. Old Craftsman lathe, I just got so frustrated I avoided parting on steel. As small lathe workarounds, I parted to get a length, maybe half the depth and sawed it from there. Almost never parted solids - going to a hole worked much better. 1340GT (+1000 lb of mass) , and input from the video, not so much of an issue. Still, geometry, speed, feed rate, lubrication, height of tool, etc. play into the equation - just not as finicky as before.
 
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