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How long should a bit last?

Posted: Sun Aug 12, 2018 10:08 pm
by 172pilot
My son is doing a boy scout project, and we're printing a bunch of signs with a #302 V_bit.. Nothing fancy.. Cutting out of pressure treated decking boards (6x1)
We cut all the boards into 2' sections, and then stained them all, and now we're cutting simple words into them using Carbide Create and Carbide motion..

The first ones looked great - Nice white interior to the wood, contrasting the dark stain, but as we've been cutting more, the cuts are a little messy, and it looks like the wood is burning a little where it is cut.. but only sometimes. The color matches the stain, so I WANT to believe the stain is being transferred into the interior cuts, but I think it's burning a little..

So, my questions are, after maybe 6 hours of total cutting, should I expect a #302 v-carve bit to be dull? Should I just replace the bit? If so, do these things get sharpened, or is it trash? I have a second identical bit, so we'll probably try just that, but I am curious if this is to be expected, or did I do something wrong??

Also, what speed would you recommend for a dewalt spindle.. It isn't marked with RPMs, just numbers (i think 1-9).. curious if the burning could indicate I'm cutting too fast of a spindle speed?

Feed speeds are the defaults for "soft wood"

ANy help greatly appreciated!!

Re: How long should a bit last?

Posted: Mon Aug 13, 2018 4:07 am
by WillAdams
Tooling life is measured in linear inches.

We have a bit on this at: --- it includes a chart which maps router dial positions to RPMs. c.f., ... peed_Chart

Cutting pressure-treated boards is problematic since they tend towards a high moisture content, and the treatment includes minerals which will dull endmills.

You can optimize feeds and speeds to make endmills last longer using the technique at: ... speeds.htm

Re: How long should a bit last?

Posted: Tue Aug 14, 2018 10:54 pm
by jfdotcom
Keep in mind heat is the worst thing for metal. The more pitch and resin on the bit, the more heat generated, thus burning and becoming more dull. In a wood like pine, your bit will get gunked up pretty fast. Something like mineral spirits or simple green will keep it clean.