Exact width dado jig with pattern bit?

[Nick2cd]

I was re-watching some of Marc's vids this morning and came across the exact width dado jig.  i was wondering if there is a good reason this won't work with a top bearing pattern bit (flush trim).  this would eliminate the need to set up the brass bushing in the router (please note, I'm very lazy and more importantly, i don't yet own a set of brass bushings).  the only hang up i can foresee is if you wanted to make a dado that is less than 1/4" deep, you'd either need to thicken the frame of the jig or use a shorter pattern bit (based on a 1" cutting length pattern bit).  what are your thoughts?

[wdwerker]

I have a set of the bushings in steel that fit my porter cable router base. They are almost an industry standard. Same lipped hole in the baseplate of many different routers fits them. Makita even makes a adapter to fit my plunge router.

You can use a wide variety of bits and bushings to suit your specific need.

Just label the jig with which bushing and bit combo you set it up for. The bushing doesn't spin and wear on the jig is minuscule .

You can set up a spiral bit if you have tearout problems. The bearing spiral bits are pricey.

[wtnhighlander]

The direct answer is "yes". I have used a top bearing pattern bit to make dados this way, and it works like a charm. Perhaps not as flexible where depth of cut is concerned, but otherwise it is fine.

[Andrew Pritchard]

I've not used a spiral bit, but I have used a straight bit. I found that the dust collection was terrible, and had a tendency to throw the dust and chips straight down the dado I'd just cut. I ended up building a replacement base mounted plate. To the side of the plate is a block of wood that my 2.5" dust collection hose friction fits to quite nicely. The first iteration had the block of wood too close to the plunge base handle so the hose wouldn't fit straight in, and had to be held by hand. Never the less, it was very successful and only a minimal amount of dust was thrown.

 

I've just finished the second base so I've not had a chance to test it out yet. The second base is the same as the first except the dust port is a little further out to take into account the movement of the plunge base.