Fly Cutting Issues

[Charley Davidson]

Benny just brought me back a home made fly cutter from one of his south west honey holes, after fixing some issues of a poor lathe turning it worked fine. I was using a carbide tipped cutter that came with it but soon went south after chipping from the intermittent cutting, a second one was leaving a mirror finish until it chipped, I ground a HSS cutter but not getting good results.

Anybody have a drawing of how I should grind my cutter and the proper angle it needs to be inserted?

 

[Tom Griffin]

Benny,

Just leave the tool square and grind 5º-10º clearance on the side and end and a few degrees of side rake on the top, but no back rake at all. A small(1/32") radius on the point will help with surface finish. The idea is the keep as much material behind the cutting edge as possible for strength and to conduct heat away from the cutting edge. All of these angle should be increased when cutting soft metals like aluminum or brass.

Tom

 

[Rbeckett]

Angles depend almot entirely on the material being worked. The info above is pretty close and will get you into the ballpark. What are your speeds and feeds as well as operation type and material. Machineries Handbook will give you a formula to determine the rotational speed and depth of cut and those numbers will spell out what tooling and what angles are required to cut material rather than abrade it off with a "dull" bit. You actually can get a bit too sharp to do it's intended operation, It's not really the bit it's the relief angles and speeds. Mr Pete222(Tubal Vain) has a really great series on you tube for off hand grinding of HSS tool bits and the correct stones to use to polish the edge back up when it does eventually get dull. Charlie I hope this non-answer of an answer helps point you in the right direction

Bob