Quote Originally Posted by Blackrat View Post
roughly how long should i expect a bit to last ?
It depends on a lot of things.

Some wood species are more abrasive than others, and will result in shorter tool life.

To maximize tool life, you want to cut at the highest possible chip load, while still getting an acceptable finish. The lower the chip load, the hotter the tool will get, and the shorter it's life will be.

I prefer to use 3/8" (10mm) bits, as they allow you to cut faster, and they last a bit longer. On an industrial machine, I rough cut at about 9000mm/min and 18,000 rpm (5-8mm/pass), and take a full depth finish pass removing about .25mm at about 3000mm/min.

I like to use downcut spirals, as they'll keep cutting cleanly even as they dull, which allows you to get a bit more life out of them. I've cut out parts from 27mm thick oak with at these feedrates and can get 8-12 hours of use before I change the tool.