Smoking with newer bit

I’ve gotten several new endmil bits and after a few projects they start to smoke the wood, I’m using pine. It’s not burning the wood and it’s not like it’s smoking out my shop but it’s visible. I’m running it at a 3 and tried turning it down. The feedtate is 1000 mm/min. Is a little smoke on used bits normal? They still looks sharp and probably only have 10 hours on them and their not cheap bits.

Depth of cut?

You may want to run faster feed rate (1875mm/min). You get more heat buildup if you sit in one place too long.


Unfortunately, endmills have to be considered consumables — but they should last longer than that.

I suspect that the flutes have gotten covered in pitch/rosin — please try carefully cleaning them with rubbing alcohol.

Occasionally one will get stands of wood which grow in soil with a lot of silica or other minerals and the minerals will appear w/in the wood structure — not sure if that happens w/ pine though.

Another possibility is you’ve over-heated the bits and they’ve lost their temper. The suggested feed rate for pine is almost twice the 1000mm/min you’re using (for a 1/4" endmill): — 10 hours is a fair bit of cutting though.

To evaluate if an endmill is sharp use a loupe to inspect it.

Did you try the test cut technique suggested here:

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Pine tends to coat bits with sap pretty fast.

You can clean them with special bit and blade cleaner, but oven cleaner also works.

Be careful of the sharp edges.