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I'm a machinist. The coatings have to do with coating the tool with another material which is harder (in general) than the material of the tool. For example, if you were to cut a really hard piece of steel you would ideally use a cutter that was coated specifically to cut that type of steel.

For wood, uncoated is fine. The more flutes, the more rigid, though. So, a 4-flute is more rigid over the length than a 2-flute. Also, something to consider, an up-spiral flute will leave you withtorn fibers at the top of the cut whereas a straight flute will take more of those away.

Hope this helps.

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Adam

Carl - that helps a lot. Thank you very much. So the non-coated is a no-brainer since I'm using it to cut spruce and the coated is more expensive. Regarding the number of flutes, I use a Black & Decker Dremel knock-off and the bit tends to wobble slightly, resulting in a channel slightly wider than the bit. It also wanders a little bit on the hard grain lines. If the 4-flute bit is more rigid, I would guess it might wobble and wander a bit less, so I think I'll give that a try.

Thanks again!

Charlie