Width of Dados

[Richard Brown]

I was just over at a neighbors house and he was building some cabinets out of plywood and some of the dados were sloopy and some he needed a dead blow hammer to get them in. I have always taken time to just keep adjusting my dado till I got a nice fit for gluing. I have just thought of something and was wondering anyone could come up with how much oversize the dado should be over the plywood? The plywood could be checked for exact thickness with a caliper and the dado could be set with shims for the right size. I hope that this makes sense. Dick

[Bill Arnold]

Richard,

One approach to cutting dados that match exactly is to use a combination joint. Make the dado about 2/3 the thickness of the plywood, then rabbet the part you're inserting so you leave the thickness of the dado. Example: for 3/4" plywood, make the dado 1/2"; then rabbet the companion piece so you leave a 1/2" tongue on it. you can put the rabbet entirly on one side of the piece or rabbet each side so you have a tongue in the center of it. This approach conceals both edges of the dado.

Regards,

[Tim Sproul]

Add the thickness of a dollar bill for a dado to accept ~3/4 inch thick material. The slop depends on the material you're joining and the length of the dado. More dense woods need a wee bit more slop than softer woods. Longer joints need a touch more slop than shorter joints. Wider grooves need more slop than more narrow ones.

Test joints......:)

[Steve Rowe]

I discovered that there can be significant differences in thickness between individual sheets of baltic birch ply. Some as great as 1/16" and I wish I had noticed this before the dados were cut. Now I check everytime for each individual sheet. I set the dado width to allow the edge to be easily inserted (no hammering) and no noticable slop.

[jack duren]

when building cabinets be sure to get materials from the same lot. like tile and wallpaper unless they come from the same lot variations will happen. each set of cabinets, etc i build i buy and use from the same pallet. if there is other materials left from a job i try and use them with caution.

if you are caught with different thicknesses. set the dados for the smallest and simply move the fence for the larger pieces. also match or number the pieces not to get confused later......jack

[Michael Cody]

I was just over at a neighbors house and he was building some cabinets out of plywood and some of the dados were sloppy and some he needed a dead blow hammer to get them in. I have always taken time to just keep adjusting my dado till I got a nice fit for gluing. I have just thought of something and was wondering anyone could come up with how much oversize the dado should be over the plywood? The plywood could be checked for exact thickness with a caliper and the dado could be set with shims for the right size. I hope that this makes sense. Dick

I have a jig I built years ago.. basically it's a slider so you put in a piece of the dado insert material .. then close the slider up on it. That sets the slot that guides your router to right thickness.. Also I added a hook so after the first dado you can set your spacing and just hook it in the dado you just cut to space the next one... I use a flush cutting bit with bearings.

See this link, this is the plan I used -- modified for the spacing hook.

Dado Jig Plan (http://www.plansnowinprint.com/adjustdado.html)

[Chris Giles]

Richard,

The answer to your question is either .005" or .010" depending on how snug a fit your after. If you need some wiggle room, go with .010", such as panels into door frames. I would use .005" for most dado work in case construction. Dial calipers are an essential tool in the woodshop, and serious woodworkers would benefit from understanding engineers measuring standards. It seems no two panels are the same thickness, and measuring in thousandths is necessary to maintain accuracy in one's joints.