making dados

[jeff oldham]

I just bought a dado blade set and going by the directions for a 3/4 dado it said for me to use the inside and outside blade and 4 of the 1/8 chippers,,which I did and it does cut a 3/4 groove but its not as tight as I like it to be,,im really new at using the dado blades,,so if anyone can help me get a tighter fit I really would appreciate it,,thank you

[Bradley Gray]

What are you putting in the groove that is loose?

[Jamie Buxton]

Jeff, that's odd. Most dado stacks would cut less than 3/4" with four chippers and two outsides. You get 3/4" dados by adding shims, which usually come with the set.

[Dick Mahany]

Double check to make sure that no teeth are touching on adjacent blades as that can cut larger than intended dados and may also damage the blades. Even if the teeth were correctly staggered, sometimes a chipper can rotate slightly out of position when tightening the stack.

I agree with others that most dado sets cut undersized dados and shims are typically used to achieve the desired width. If you have a pair of calipers, carefully measure the outside maximum width of the stack. See if the width seems correct.

[Mark Daily]

What are you putting in the groove that is loose?
My first thought also because 3/4” plywood really isn’t a full 3/4”.

[jeff oldham]

I am cutting in 3/4 plywood

[Steve Eure]

Jeff, most 3/4" ply is not actually 3/4" but a fraction less. If you are thinking that the material you are using is 3/4" and it's ply, I'd mic it to see. You stated that your dado stack is measuring 3/4", so I assume your material is not 3/4" that you are trying to insert. If that's the case, you will need to reduce your stack by replanting one of your 1/8 chippers with a smaller chipper and some shims. Some dado blades contain a 1/16" and sometimes a 3/32" chipper to account for this. Then it's trial and error using shims to adjust.

[Matt Day]

Steve’s got it. Use the chart as a starting point, with no shims. Do a test cut and using the board that will be inserted in the dado, see if the dado is too big or too small. Adjust the dado stack from there.

Cheap plywood will vary in thickness even within the same sheet, FYI.

[ChrisA Edwards]

And if you can't get the exact fit, your require, in one pass, reduce your stack and make a couple of passes creeping up to the desired width.

[Rege Sullivan]

You've gotten good advice here. One thing I will add... mic plywood in several places and average the measurement before setting up your stack. Keep a log of the measurement and the stack setup with your dado set. Nothing fancy necessary, mine is on a piece of cardboard. After a few times you can usually get the stack right on the first try.

[Dan Jansen]

I prefer to cut 1/2” dados and then a matching 1/2” rabbit on the plywood.

[jack duren]

You need to number cutters with shims to get the same setup each time. I just use a permanent marker. This will save you time for future setups. After a set is sharpened you'll need to reset your numbers and shims..

[Rick Potter]

As mentioned above, some plywood varies in thickness within a single sheet.

I once bought some Home Depot plywood, and got my dado dialed in on one sheet, in one spot. Then I cut all the dado's for a whole shelving unit and found they were too narrow because the thickness of the shelves varied, and I had used a narrow place to check the size.

Looking at al the edges of the already sized shelves, I could see overlaps in the layers, making some areas thicker than others. The only way I could finish the project was to widen the dado's, which made some a bit sloppy.

Just another learning experience. Thankfully it was just a utility unit for the garage.

[Bradley Gray]

Rick, I had a similar experience on a shelving job with over 100 shelves. The thickness was all over the place.

I ended running both ends of all the shelves on end with the saw set to the dado width.

Put all the rabbets down and it worked out but ate a lot of time.