Dewalt Bit Centerline to edge of guide distance

Hi Hillary, are you cutting a dado, an elongated groove? I couldn't quite understand what you were trying to do. With that in mind, an exact fit dado jig can really make this happen easily. If you are certain the thickness of the piece fitting into it is 23/32nds (18mm metric) you can use a mortising bit with a top mounted bearing and a straight edge (a very straight board), and do it freehand. Use a marker to put a spot on the rim of the router base and keep that spot next to the straight edge. If you rotate it, the groove will wander slightly.

I'm assuming you're doing this freehand not on a table. Clamp the straight edge in place so you can make several passes of about 1/8th inch each. The bit I have in mind is fairly common and looks like this mortising bit. Mortising bits leave a very flat bottom to the cut.


If you are cutting close enough to the edge, you could also use an edge guide like this:

Hi, I just realized I forgot to attach the edge guide picture. I added it above. The flat bottom mortising bit is good because it makes better glue contact with the edge of piece fitted into it.

Dados are grooves that go from edge to edge. A groove does not go all the way to the edge. Look up exact fit jigs. You can buy one already made, or make your own. If you make your own, it looks like this: If you are fitting a shelf, for example, you slide a piece of the shelf into that gap and snug the wider piece up to it, and use a bit with a bearing on it, and that is a little over half the width of thickness of the shelf. You make one pass riding the bit against the top or fixed side, then again on the movable side. You make it much longer than any thing you expect to make. The trick is to make certain the top cross piece is exactly 90 degrees to the side pieces. Being careful about that (using an engineer's steel square), will make it really easy to use and very accurate. One last thing, My gadget requires using what's called a spiral bit. The shop made jig uses a much cheaper mortising bit.


Here is an exact fit setup from Rockler woodworking. You fit the sliding part into a groove on the long clamp. The long clamp has something to grip the edge, but it doesn't take very much to make is shift, so clamp it down.


I have an old gadget called the Dado Wiz, now discontinued, that I use and it is really nice, but I have to make sure it's lined up just right using a tape measure. If I'm doing a shelf or any similar thing that has to be exactly parallel on each side, I will cut the big plywood sheet to the height and then a little wider that double the width of the side pieces (cabinet or bookcase), cut the dados straight across, then use my table saw to split the two sides and trim them to the final width. But I'm a fuss budget about such things.

DeWalt makes an accessory dust collection attachment for the 618's plunge router base. This would be a nice accessory when cutting almost anything. Routers are notorious for creating and launching sawdust into the air. This would reduce almost all of that nasty sawdust. Compact Router Dust Collection Adapter for Plunge Base | DEWALT



This is a minor point, but I keep an extension cord hanging down from above my workbench so I can plug in but keep the power cable out of the way.