[Herb Stoops]

I had a Grizzly shaper one time and it had a router bit chuck adapter. I tried router bits in it and did not have great success. The shaper turned at too slow of rpms for the 2 flute router bits, Shaper bits are a minimum of 3 flutes,so the cutters are cutting 1/3 more per rpm. I finally sold it and bought a router table and mounted my router on it.
Herb

 

[Herb Stoops]

Number of flutes is not the issue. A 3 flute tool cuts at the same speed as a 2 flute tool. It just takes a shallower cut, all else being equal.

Now think of what’s happening when you cut wood. A two-wing router bit at 21,000 rpm provides 42,000 cuts per minute, which is part of the reason for the great cut quality you typically see from router bits. A two-wing cutter in a shaper at 10,000 rpm would only provide 20,000 cuts per minute, so cut quality can suffer. The solution? Most shaper cutters are four-wing instead of two-wing which, as a rule, also makes shaper cutters more expensive than router bits.

Herb