Another way.....

Often people use a kerfmaker like the one I showed in an earlier post to help make perfect dados for mating parts.
But there's another way I often use that's just as quick and simple to do. 

The details
 

You'll need a gauge (of sorts) that takes into account the mating part thickness and the saw blade kerf. Here's how its done.

Set a fence stop approx. 6" from blade but this doesn't have to be exact. Once you cut the scrap length the fence stop does not move.

 

 

 

Next, you insert the mating part (This will be the part that inserts into the finished dado; marked "A") between the scrap length you just cut and the stop.  

 

 

Then you cut off the portion sticking out from the left of the blade. This is now your gauge. Seen here with a "star". Save this piece. You will use it to make your perfect dado.

 

 

Set your blade height for the dado depth. Make your first cut.

 

 

Insert the Gauge and make your second cut.

 

 

Remove the waste in between the two cuts.

 

The Perfect Fit!

Now you'll have perfect fitting parts!

 

 

Thanks for looking! 

Cheers! 

MrRick 

Edited December 1, 2025Dec 1 by MrRick

Interesting. I’d have to use that procedure a bunch of times to remember the steps. 

Lew... after a few times it's easy to remember. Print it out and have it next to you on your TS. Give it a whirl. 

Thanks Rick for the idea and instruction tutorial.

You're welcome @Grandpadave52

Edited December 3, 2025Dec 3 by MrRick

@MrRick I want to thank you for sharing this tip. As a novice, more of a tinkerer than a woodworker, I have failed more than once trying to cut tight fitting dados using a router. I tested your method today and take it from a fool, your method is almost fool proof. I found from the test that not all 1/2" or 3/4" sheets are exactly the same thickness but by using a scrap piece from the wood I am actually going to put into the dado to make the gauge piece it will be a tight fit every time.

Now you have given me the confidence that I can make more than just sawdust and noise. 😁 

Edited December 4, 2025Dec 4 by Bubba

@Bubba  You're welcome!! And thank you so much for your kind and honest compliment and reaching out.  I really appreciate it. When sharing it is always my intent to help others. I'm glad it works for you. 

Cheers! 

MrRick