Thread: Furry edges when cutting mortises with router

Hi. I'm using a router, in a router table, running a 6mm square bit to cut some shallow mortises. The problem I'm getting is that the edges of the mortise are furry - in other words little whiskers of grain remain affixed, rather then getting a clean cut across the grain. These whiskers are surprisingly time-consuming and damaging to remove by hand.

I'm using an older Makita single speed (22000 rpm) router. If speed is the problem, I could modify the router table to take a variable speed router, but its a lot of work so I'd like to be sure it is the most likely problem first.

I"ve tried two 6mm bits, both midling quality but both new. I'm doubting that the quality of the bits is an issue as both are new, so even if poor quality they should cut cleanly for a short while (shouldnt they ??).

Other info - timber is cedar, blackwood and some other unid timber. Mortise is 1.5mm deep.

Any advice.

cheers and thanks
Arron

Arron.

One trick you could try, after getting your mortises cut. Is to let your Router run back the way you have just cut.

This method works quite well on a table router, so I don't see why it should not work for you.

The other question of course is, does the "whiskers" interfere with your work.
Some roughness to a surface, can help glue bonding.

Paul.

I have found the soft timbers do tend to tear a bit but hardwoods don't have that problem. Well thats what I found anyway. As Paul mentioned, is it such a big problem, the furry edges should be hidden by the tenon shoulders in my way of thinking. have you tried using an up spiral bit?

thanks guys
I've done a bit more research on this and the best solution I've found is to use a spiral down cut bit (not upcut, but down cut). I havent tried it yet, but I'll get one and post the result.

I should have pointed out that the mortise are not for a m&t joint, so they are fully visible.

cheers
Arron