Re: Carbide - Surface Finish - 9A

Bill in OKC too

When I got my first lathe, an HF 7x10, all I could afford was the cheap brazed carbide they sold, and it was definitely crap. The chips of carbide were not ground at all, and the they were brazed on blanks that presented the bottom edge of the carbide chip out in front of the top (should be cutting) edge. Everyone said you needed silicon carbide (green) grinding wheels to reshape them to be usable, but I was able to do it on an alox (gray) wheel. Still not the greatest tooling, but better than when I bought them. However, my 7x10 was not sufficient machine to use them, and I wasn't sufficiently good at machining to get any usable work out of them. Something about not being able to measure accurately... ;)

I still have them here somewhere, may try them on the Atlas if I can manage to finish setting up the shop. I had my 2nd cataract surgery Tuesday, can't lift more than 10lbs, not allowed to bend 90 degrees at the waist, and not supposed to do anything like normal activities for at least a week. Good news, though, is that I can see well enough to drive and read with my old glasses. I'll get a new prescription in about 2 weeks, but no shop time for the next week, so I don't really need the new glasses. And I can read micrometers and calipers just fine as is! 

Bill in OKC

William R. Meyers, MSgt, USAF(Ret.)

Aphorisms to live by:
Good judgement comes from experience. Experience comes from bad judgement. 
Improvise, Adapt, and Overcome.
Physics doesn't care about your schedule.
The only reason I know anything is because I've done it wrong enough times to START to know better

On Thursday, July 14, 2022 at 10:34:23 AM CDT, m. allan noah <kitno455@...> wrote:

I've had better luck using sharp, positive rake inserts intended for aluminum, even on steel. I've not found the negative rake or brazed carbide to be useful on a light lathe.

On Wed, Jul 13, 2022, 10:46 PM Mike Poore <mpoore10@...> wrote:
I am sure this is not the first time for this topic, but I'd like to know what setup, if any, anyone has found that provides a good surface finish using carbide on 1018?

I have acquired a lot of carbide inserts and holders along with my QCTP. I have negative rake and no rake holders. I have chipbreakers and flat carbide. I turned some aluminum after rebuilding the lathe and the surface finish was as good as one could expect so far as it was nearly a mirror finish using the slowest feed. Then I tried 1018 with the same tooling and ended up with a fairly rough finish. It looked and felt like the metal was tearing rather than cutting. I have tried other combos and nothing yet is satisfactory. I have a diamond disc sharpener, but I think the carbide is sharp enough to do better than it is. There is plenty of HSS laying around that could be used, but the idea of indexable carbide would be preferred if I can make it work.

There is plenty of experimenting left to do. I was hoping someone could give me a starting point as far as insert shape, rake, speeds (I am guessing it might be a little different than what the book says for an old WWII cast iron bearing lathe.), and tool angle. Thanks for any help.

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