Got to chime in here. I was a tool and die maker on the bench for 10 years after a 5 year apprenticeship. I am extremely experienced with end mills, carbide and steel. I have been using them for 25+ years as router bits and have never had an issue with them in performance or safety. As a matter of fact, when woodworkers were first introduced to "solid carbide spiral up-cutting router bits", I have more than a suspicion that they were just repackaged carbide end mills sold to the wood working trade.
The big disadvantage used to be the cost of the carbide endmills, because of the labor and cost of the diamond wheels needed to shape and sharpen them. Today, with 6 axis CNC grinding machines, manufacturing carbide end mills has gotten faster, cheaper and better. Many carbide end mills today are made for high speed milling of hard materials, so 30,000 rpms means absolutely nothing to a 1/2" solid carbide end mill. Some run at 60 to 100 K rpms, but have to be balanced in the tool holder. I regularly run 1 1/4" long fluted, 2 flute spiral carbide end mills at full speed in my 1400 and 2200 routers. If you are running longer flute lengths, then you need to dial the speed back. Carbide tools will not whip like steel, because they have hardly any elasticity in them. They are very ridged and will simply snap off if they get too far out of balance (not a good thing). Carbide has no modulus of elasticity- that's what makes them more ridged and reduces chatter. When I use 3" long flutes in the router, I turn the speed down.
End mills are available in many shapes and sizes- flavors if you like. The fewer the flutes, 2 vs 4, the more chip clearance you have allowing for deeper cuts and faster feeds. 3 fluted mills cost more, but have better harmonic balance at high speeds and a good amount of chip clearance. In my experience, 2 flute standard length, 1/2 dia are the standard. Typically expect feeds to be faster for routing than milling,because in milling the feeds are controlled mechanically and a slow and steady feed is easy to do on a machine. Hand routing tends to get faster feeds because you are driving the router and it's very difficult to feed slowly and steadily for a long time.
4 flute end mills are OK if you are wanting to trim and edge, like edging Corian before seaming. The spiral flutes of the end mill actually do a better job of edging, because of the shearing action of the cut. Using a spiral flute is like angling your hand plane and gives a more slicing cut than just a standard straight fluted router bit. I have machine thousands of inches of solid surface material with carbide endmills and have never encountered any difficulty.
I know for a fact that the 2200 router will bury a 2 flute solid carbide endmill in walnut 1 1/4 inches deep, and with the dust extraction on that machine, chip clearance is not an issue at all.
Almost all 2 flute end mills are "center cutting" , which means you can plunge cut with them. Most solid carbide endmills are center cutting these days, because they are sharpend and fluted on CNC machines held in collets. Some of the older High Speed Steel endmils are not center cutting. Just make sure when you look at the end, the face cutting edges meet in the center of the cutter. If there is a small hole in the cutting end of he mill, it wont center cut.
Make sure the shank of the endmill is clean and free of oil when you put it in the router, and put the end mill shank in all the way, then back out 1/8" before tighten the collet. The polished carbide is slick, so I tend to tighten the collets a bit tighter on carbide shanks than on Steel shanked router bits.
Festool makes a 3/8 collet for the 1400 and 2200 and those are very handy because the standard shank for most end mills (High Speed Steel) under 3/8 cutting diameter is 3/8. It would be very handy to have some 1/4, 3/8, and 1/2 solid carbide two flute endmills for wood working. You can buy them cheaply at machine suppliers like MSC. The imports are getting better in quality all the time.
Be very careful handleing and storing the cutters. The carbide tips of the cutter can chip on the corner of the tip, and that will cause poor finishes and cutting problems. The carbide tips are very brittle. Experienced toolmakers round the cutting tips with a diamond hone most of the time ( about a .005" rad), but it is tricky to do correctly- your tool sharpener (guy or gal) can do this for you. The .005-.010" radius will increase the tool life 3X if done correctly. Once the tip chips, it's a whole nother ballgame.
Just some general thoughts- Hope this helps someone
Jay
