I used to swear by running my end mills at the book speeds until a job in Tacoma last month proved me wrong.

I was burning through tools on a simple aluminum job until an old-timer on the floor asked if I'd checked the actual chip load with a microscope, which showed my 'perfect' feeds were just rubbing the material.

3 comments

3 Comments

gavine413mo ago

But come on, how many shops are really burning up that much money? Most guys I know just run the book numbers and get the part out the door.

claireg813mo ago

Wasn't there a big thread on Practical Machinist about this exact thing? Some guy posted photos of his chips from a 6061 job. The book speed gave him dust, but when he bumped the feed way up, the chips actually curled and came off blue. He said the sound changed from a whine to a rip. Makes you wonder how much time and money gets wasted on "perfect" settings that are just wrong for the real setup.

webb.jordan25d ago

So you're telling me all those years I spent memorizing feeds and speeds charts was just a rehearsal for the part where I have to listen to my machine like it's whispering secrets? @claireg81 probably saved me a few thousand dollars in broken end mills just by mentioning that thread. I had a job last month where my "book perfect" setup was making pretty dust clouds while the chips looked like sand. One bump up in feed and the machine started sounding like a angry cat, but the parts came out perfect and the tool life tripled. Makes you wonder if half the guys who swear by the charts are just really good at changing tools.