Ran a test cut on some 6061 with a 1/4" endmill at 500 sfm and got a crazy smooth finish, way better than the book said.

3 comments

3 Comments

Yeah, the book feeds are always so conservative. I pushed a 3/8" tool in 6061 way past the charts last week, just as an experiment. The finish was like glass, and the tool didn't even get warm. Sometimes you just have to ignore the manual and send it.

derekjenkins1mo ago

My old foreman would lose his mind if we went off the chart speeds. He swore by the book numbers for everything. Then I saw a guy running a half inch bit in some steel plate at almost double the feed... the chips were coming off blue but the cut was perfect. Made me realize those charts are just a safe starting point.

bettywood25d ago

Thing is nobody talks about how the machine itself changes the game. @derekjenkins mention of a guy running doubled feeds on steel got me thinking. I tried running a 1/2" rougher in 7075 at 250 IPM on a old Fadal and it chattered like crazy. Same tool same settings on a DMG Mori and it was smooth as butter. Charts don't know your spindle taper condition or how rigid your machine is. You gotta feel it out.