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Hello,
Hoping to get some opinions from the many talented folks on this board. I am running a 1/2" 3 flute spiral up-cut ball end on my Dewalt router equipped 3925 for the bulk of my work. Things are going relatively well, but I am seeing burning in areas where I shouldn't be, I can attribute most of this to slow feedrates, but am wondering if a 2 flute would be a better "go-to" bit for the major bulk removal work. Also wondering on opinions between the longevity of Carbide vs. the initial sharpness of HSS.
Thanks for your time.
Mike

All my go to bits are carbide two flute but, I've only been doing this for about half a year. I'd suggest investigating downcut bits though as they tend to have a lot less tearout and push the work into the table as they're cutting. There is the issue with chip clearing but that hasn't been a problem for me yet.

As to sharpness, initial sharpness and longevity seems to be directly proportional to price. I've had very good luck with $8 1/4" carbide end mills but compared to the Onsruds I picked up on e-bay (for not much more) they're in a different league. I got a specialty bit from Vortex and you almost couldn't touch the flutes! (it was on sale for like $95 too!).

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

There needs to be something for the tooth to cut. Slow feed rates, high RPM reduce the chip load. You'll get better results with 2 flutes rather than 3. I'd also play with the RPM if you can't increase the feed. For 1/4" and under we've gone to single flute bits. Way better!

Don't use ballnose cutters with an odd number of flutes, that means they only have one center-cutting flute instead of two and will leave a poorer finish and wear more quickly near the bottom of the cutter. Three flute straight cutters are fantastic for slotting and I use a lot of them on wood and aluminum, but they do leave a poorer finish on floors due to the single down-cutting edge and they're easier to clog up.

If it's a generic cutter with four flutes or more then it probably has poor geometry for wood cutting as it is likely a 'general purpose' or steel cutting bit, and if it has more then it's definitely not a cutter you want to use on wood. I have some four flutes that work well on wood, but with hobby CNC routers the feed rates are already so far behind the RPM of the spindle that adding more flutes is making a bad problem worse.

The 'HSS is way sharper than carbide' thing is a holdover from ancient times, I've found it to be universally bad advice with modern cutting tools. The grain size of carbide today is quite sufficient to make razor sharp cutters, and I've got a nice bone-deep scar on my finger where one slipped from my hand in a moment of distraction. Tools from any manufacturer which are specifically designed for aluminum cutting tend to be sharp to very very sharp, and stuff from the specialty wood-cutter companies like Onsrud is going to be very sharp also.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Thanks very much for all the information.
Mike

The general rule to take away from this statement is that it's best to make chips instead of dust. Cutters work best in the long run by having something substantive to cut instead of shaving the surface. They will stay sharper and last longer if you program your spindle speeds and feed rates with this in mind.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Just wanted to say thanks again for all the info. The two flute carbide is a champ!