[Hammerli]

Is there any big difference in using an upcut or downcut spiral bit in the router? I've read about the surface finish and chip ejection, but does it really matter which bit is used in the router for a table application or for using the router by hand? Does the finish matter when making, say, a mortise and tenon?

 

[kp91]

It depends on what you're doing. If you are mortising, upspiral is the way to go. If you are cutting a dado in veneer plywood, downspiral works pretty well.

In general, I have more upspiral than downspiral bits, since they cover a greater range of jobs quite well.

 

[jerrymayfield]

Due to its geometry an upcut bit tends to lift the chips from the cut,which is what is needed most times. The only time I would ever use a downcut bit is on the edge of a board where the chips have a place to go.

Regards

Jerry