View Full Version : how long should a bit last ?

18-12-2014, 06:06 PM
roughly how long should i expect a bit to last ?

cutting anything from pine to oak to blackwood etc (medium hardness woods)

ive been using a 6mm twisted upcut bit and i only get about 3 hours continuous cutting , feeds are about 3000mm/min at anything from 12k to 24k/rpm , lower rpm seems better

would a parallel bit be better suited ?

18-12-2014, 06:18 PM
I only use upcuts for pockets so it clears the chips, downcut when I don't want to chip the top edge, parallel for everything else. It's best to rough out using parallel bits then use your 'specials' for a final finishing cut. How long do they last ? good question and something I can't put a figure on. If you use oven cleaner to keep them clean and tickle them with a small diamond stone they last a lot longer.

There's this thread also; http://www.mycncuk.com/threads/6969-Tool-Life-Expectations?highlight=roughing+cutters

18-12-2014, 11:53 PM
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.

21-12-2014, 11:04 AM
thanks for the replies ! and the link !

one of the areas i think i can improve is to ramp into the piece and not plunge ...

my pockets are only 10mm wide ... and there are sections that are 6mm wide so i can only use a 6mm bit

i changed to 4mm passes to go down 11mm , i was doing one pass at 11mm , however holding the work piece was a bit of a challenge but i have made a jig now so will change back to 11mm passes as this seems to be better on the tool

but im gonna get some parallel bits as they can easily be resharpened down the road from me