Router Dado Problem

[Herb Smith]

Using a PC 690 with plunge base. Trying to cut ¾" wide x ¼" deep dado in plywood. Cutting in single pass using an almost new ½" shank Whiteside dado bit. Each dado I've cut in my test boards leaves a lot of "fuzz" (although it is more than that) at the top on both sides of the dado; in other words, it is not a clean cut at the top. Not sure what is the cause. Should I be making a more shallow pass and cutting the dado in two passes? The bit shows burning. Appreciate any feedback.

[pat warner]

X- grain, spiral cutter? Then not unexpected.
Take shallower passes no matter.
1/2 x 1/4 is too much wood waste/shot.

[Jerry Miner]

pretty normal. IME. I go over these cuts with a sanding block and 180 paper.

[glenn bradley]

I'm with Pat in that I would take a 1/32" to 1/16" first pass and then probably two more at about am 1/8" per. General rule of thumb maximum cut per pass on a router is 3/8" x 3/8" in area. 3/4" wide by 3/16" would hit this mark.

The symptom can be caused by several factors. The bit should cut cleanly if the bit speed and feed rate are close to correct. If the bit and feed rate are good and fuss still appears, its the material. A scoring line can solve this but, can be fussy on a dado. Cheap ply is a common cause where the veneer is thin or of poor quality. A jig that provides a sort of zero-clearance function can help as well and is handy if you do a lot of longer dados.

316696

[Don Jarvie]

If you need a clean edge you can score each side with a knife and it should prevent the chipping.

[Mel Fulks]

A single flute bit will cut much faster. IMO there is not much need for two flute straight router bit ,much slower than single flute and burns much more.

[Victor Robinson]

What kind of plywood? Some are more prone to this, especially cross grain.
If it's light fuzz, usually knocked off easily with some sandpaper.

If it's very bothersome, take a scoring pass 1/16" deep. It's probably a dado size I'd be doing in multiple passes, especially with a smaller router.