Joe Jasper

Exact Dados

Exact dado jig

What is a kerfmaker? Have you ever heard of bridge city tools? Before I tell you what a kerfmaker is you should check out first. I’ll wait. alright are you totally blown away by this little tool company that makes this crazy awesome stuff!! Yeah me too but there’s one problem….. I’m pretty sure i don’t have to say it so let just say we are going to build a kerfmaker.



The idea behind the jig is pretty simple, make perfect sized dados for what ever workpiece you reference. It does this by giving you two positive stops to reference any fence from any power tool off of, one stop for the first pass of the slot and one for the second pass. The resulting dado width will be exactly the same width as the piece of stock you referenced it off of. That might have sounded a little confusing but it’s really not, just kinda hard to explain.


if you take a look at the kerfmaker picture above, you will see three outside surfaces. one end of the jig has one surface, the other end has two, one being movable. To calibrate the jig you first set the thickness of what ever blade you will be using (dado, bandsaw, router) this is done by moving the orange piece in towards the blue piece the thickness of the blade. then you must gauge the thickness of you stock by placing it in-between the silver stop and the blue stop (picture below). Now you will end up with an offset at one end of the jig.

This offset is the amount you will have to move you fence over to get a precisely fitting slot. By clamping a stop on your table saw top you can use the kerfamaker a flip stop allowing you to move your fence the perfect amount every time.

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If your still confused on how the jig works, don’t worry half-inch shy  explains it much better on a video here:

I gotta make sure I give full credit to bridge city tools for this cool little jig and even though most of their tools are quit pricy, the kerfmaker is actually not that expensive so if you don’t have the time to build one I would highly recommend checking bridge city out.

I decided to make one of these jigs some time ago and actually ended up building it out of aluminium. To be honest I never even gave much thought to building it out of wood. I guess I thought it would have to be bigger than the kerfmaker to get the room to cut the grooves. About a year later I was searching for a project and I came across a few made of wood. Even though the one I made works great I thought I would take the time to build one out of wood so I could show the build process on my YouTube channel. The only difference between the metal one and the wood one is I used a sliding dovetail on the wood one oppose to just a slot on the metal one.

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I roughly scaled my kerfmaker to the pictures on BCT website. I’m not sure how close I actually am to the original size because I never actually had my hands on one but I think I’m pretty close. the over all length is 4″ by 1 5/8″ tall and 3/4″ wide.


I used 1/4″  by 3/4″ set screws and 1/4″ thumbscrew nuts for hardware. The grooves are milled using a 1/4 end mill which works perfect because the height of the thumbscrews measure 3/16. The top groove is 1 1/2″ long and the bottom groove measures 3″ the moveable stop that is used for setting the kerf measures 2″ and the moveable stop that is used for scaling your stock measures          2 5/8″. All this gives a capacity of an 1 5/8.