cast iron and cutting speeds

[boatmadman]

Here is a pic of a test piece of cast iron. Diameter 12mm, hss tool sharpened and centered for the test, lathe speed 400rpm.

I got the speed from a chart passed on to me from an experienced model machinist.

The final cut was 0.001"

Question is, how do I get a better finish?

Ian

[Gerhard Olivier]

I would try to put a small round on the cutting tip with a very fine stone- The finish you get is a copy of the finish on the cutter.

And go for the slowest power/hand feed u can. 


I would also cut 12mm bar a lot faster (950 RPM)- but don't do that till you have other answers.  As far as I know faster is wrong but works for me.

Hope this helps
Gerhard

[Darren]

I'd try both of Geroli's suggestions..........

[bogstandard]

As Geroli suggest stone a slight radius on the tip, and while you are at it, stone the ground surfaces as well.

The look on your tool edges resembles a sawtooth, they should look polished and razor sharp. A normal chisel sharpening fine oilstone will do you for now, and can be picked up at market stalls for a couple of squid. You only need to sharpen the very fine cutting edges, not all over where you have ground.

The finish on the turned metal should be like polished steel.

Speed and feed charts are NOT foolproof, they are for a rough guidance only. They are really for use in production work, where they can have total control over the material specs and machining tolerances.


Bogs

[boatmadman]

Thanks for the help fella's.

Been playing around and got a better result, not brilliant, but a great improvement:

Where can I get good information on cutting speeds?

Ian

[NickG]

Speeds and feeds will probably be different for the tipped tool you have there now. Try the hss tool with the slight rad as suggested, you might be pleasantly surprised. I would probably use about the same speed you did with HSS.