Turning a reduced section?

You might create the square corners by plunging in with a parting tool at each end of the small diameter section. You could actually rough the whole thing this way starting at the tail end and moving toward the headstock. You could (carefully) even use the parting tool for a cleanup pass. Not conventional, but I've done this. Randy

Yeah, what Randy said. If you have trouble with chatter, you can even grind a small V in the center of the parting tool so you have minimal contact with the part. It, too, requires proper relief, so pay attention when you grind it. As long as you keep the tool parallel with the turn, you can achieve sharp corners and a straight turn with no steps. You can usually align the tool adequately by sight by lighting a sheet of paper below the part in question, and align the tool to a portion of the surface that's already been machined. Shade to turned portion so you don't have any light spilling on it---otherwise you can't really see if you're in intimate contact with the tool. It helps to keep the length of the parting tool as short as possible. I hand grind parting tools (from HSS blanks) and usually have one on hand that would serve the purpose.

Needless to say, if your part will tolerate a corner radius, be certain to grind or hone a small amount on each corner of the tool.

Harold

Ayup.

Gunner

"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences."

- Proverbs 22:3

snipped-for-privacy@alum.mit.edu (Doug White) wrote in news:Naadnc541O3YRt7YnZ2dnUVZ snipped-for-privacy@rcn.net:

The best method would be to rough out the undercut section by plunging with a groove tool and then use a skiving tool to finish.

You can also skive without roughing, which would be the best method, but I don't know how rigid/powerful your lathe is.

In leiu of skiving you could rough out per above and then use the groove tool to take a finish pass. Leave around .01" for the finish pass.

There are carbide parting tool inserts designed for light sideways cutting as well, precisely for applications like this, where it helps a lot to be able to make the whole groove with one tool..

Easy to find example is

Kristian Ukkonen.

First leave as big a radius as possible at the shoulder. Steel is generally notch sensitive.

For the blending and nice polish, I would use a file while turning on the lathe. Best if you have a file made for using on a lathe.

Dan

Best if you have a file made for using on a lathe.

What would that be other than having a big, blunt handle on it? Randy

A single cut file with a long angle on the teeth and no teeth on the edges. Sold as lathe files at industrial supplys.

Dan

Absent those being available, get a "safe edge" file. They usually have the shallower cut angle, but otherwise are suitable.

LLoyd

I knew about "safe" files but not about the tooth angle difference. Randy