Router bit burning!

[Peter Pedisich]

Hi,

...tried out this bit today (41426 - Super Plunge) by Amana
http://www.amanatool.com/bits-fv/41410.html

It's a 1/2" dia carbide tipped straight bit with a piece of carbide between the two flutes which according to Amana makes it "Ideal for mortising and other plunging operations".
Trying to plunge into the end grain of 5/4 white pine it started to burn quickly, smoking as in smoke and another 2 seconds probably in flames.

I was running it at speed 5 on my router, which I believe is close to 19, 20k rpm. And plunging firmly but not too slowly.

I guess I should have listened to the folks here and got a spiral upcut!

Any idea why this happened? Is Pine the culprit? or end grain?

Thanks for any help.

-pete

[glenn bradley]

Spiral would be best IMHO but you could try a slower speed.

[James Hart]

How deep were you going and how many passes were you making to get there?

[Lee Schierer]

I believe your problem stems from two things. One pine sawdust is realtively gummy and would not come freely out of a very deep hole with a straight fluted bit. Second cutting into end grain is not an easy cut for a router bit the resulting shavings will be quite small, but the volume of those shavings will be quite large. The lack of curved flutes to lift the shavings out of the hole would leave those shavings in the hole to compact and get hot. Unless you are plunging to make an elongated slot or other type of hole significantly larger than the bit diameter, you would be better off with an up siral fluted bit or use a twist type drill. Even a forstner bit would get hot and possibly burn as it is not capable of lifting the chips out of the hole being made fast enough to prevent undue friction.

Try making the hole depth in several passes by lifting the bit clear of the wood several times to allow shavings to be thrown off or drill an undersize hole and then plunge the router using the hole as a pilot or just use a dril bit if it is a round hole.

[Peter Pedisich]

thanks, guys. I was plunging 1" deep in one pass.

My method for mortises has been to route overlaping holes, and then clean up laterally when those are done.

I'm going to try what you said, testing another hole at slower (12-15K RPM) speed and if still burning, I'll just get the solid carbide spiral upcut.



Thanks,

pete

[Brian Gumpper]

Solid carbide handles the heat a lot better than braised tooling and heat will kill the bit. You're probably getting waste packing on the face of the bit too, make sure it stays clean.

If you don't have many to do, consider a HSS spiral bit too.