Last fine cut chips tool

[Thomas GudeParticipant @thomasgude37285]

Hello,

Last night I was turning the face of a 1/2" thick 4" x 4" mild steel plate to half thickness leaving a 2" dia. circular boss in the middle (I can supply a pic if my description confuses). I was taking cuts at around 8 thou at a time happily swarfing away at 600 rpm. When it came to do the final 2 thou cut to leave a nice finish however I really started struggling.

What happened was, with the cut being so small, when the edge of the work approached the tool (cutting from the outside in) it simply chipped off the nice sharp end, leaving nothing left to cut with. I assume this is because there is less "meat" of the tool digging into the work so the tool just gives way. When it was constant cutting nearer the middle (i.e. the tool never leaving the surface of the work) it was okay but that left a stepped surface.

Resharpening and reattempting did nothing to remedy this and I made such a mess I ended up having to take a thicker cut again and leave it at that. I was using HSS tooling with a rounded point.

I wonder if anyone has any wisdom to offer on this and suggest anything that may help me in the future?

Many thanks

Thomas

[Thomas GudeParticipant @thomasgude37285]

[Ian S CParticipant @iansc]

I would suggest that 600 rpm on a 4" x 4" face would be a little fast for HSS, I'd try 350rpm on my lathe, maybe even less, 130rpm is the next one down, I use that on 6" dia stuff, except some discs I get that are gas cut, then it's back gear, and 60rpm, nothing wrong with going slow. Ian S C

[Thomas GudeParticipant @thomasgude37285]

Thanks Ian, I chose the faster speed so that I could get a nice finish – how would you get a nice finish at such slow speeds?

Would reducing the bottom clearance angle of the tool help? More material underneath making it stronger.

T

[Ian S CParticipant @iansc]

You would just reduce the feed by a similar amount, which will happen automaticly if you have power feed.

Ian S C

[Author]

Posts