Cutting dados is one of the necessary wood joints in woodworking. It is used in many forms of furniture, shelving, cabinetry, tables and much more. Dados are simple in design but can be very strong because they are supported along their length, but in order to be strong the joint needs to be fairly snug, and this is where the kerf maker can be an irreplaceable tool.
Watch it on Youtube: https://youtu.be/yHc0Xr2hXQ4
The form I am making in this video is one of the simplest types I have seen and can literally be made in a few minutes and give accurate results right off the bat ...
As it turns out, you can make a Kerfmaker as big or as small as you like. I made this one a little bit larger so that it was easier to photograph and to demonstrate, and working with wood that is somewhat larger is also good.
The Wood
It is important to make this jig from hardwood for a couple of reasons, first of all, it's good to have the weight of hardwood, to help get accurate settings, and secondly, you will need to glue end grain to long grain and hardwoods are more predictable for gluing job.
I started off with a couple of pieces of hardwood that was 1-1/2" x 3/4" x 7" long. The length is longer than I needed but I expected to trim ends to bring it down to 6 inches.
Cutting the Rabbets
The first thing you need to do is cut rabbet in the side of each of the hardwood pieces. You can do this with a table saw or a router. In my case, I used a router to get a little bit cleaner edge. As you can see in the video, it will be IMPORTANT that the 2 pieces align evenly along their edge because the bold the washer that will ultimately hold them together will need to have an even surface to adhere to when locking the 2 sides together.
Measuring Bars from Amazon
Hole Drilling and Countersinking
The 2 pieces of hardwood are held together by a bolt, a washer, and a wing nut. The hole for the bolt needs to be as close to the joint as possible without cutting into the rabbet edge. The best way to do this is to use a washer the same size as the head of you bold, then, then using the extension side of the rabbet on the opposing hardwood, mark the center of the washer that will later become the hole for the bolt.
BUT FIRST ... you need to drill the countersink hole for the head of your bold, and the best way to do this is with a Forstner bit. This will then also give you a small starter hole that you can use to drill the through hole that will accommodate the bolt,
Attach Wooden End
There needs to be a small wooden end attached to either one of the 2 sides. The quickest way to do this is either 2 part epoxy glue, or use a Cyanoacrylate glue like Super Glue and an accelerator and your joint will be done in seconds, but make sure the joint is square to the hardwood side. When this is done and checked, now is the time to trim off the other sides to make sure the back of the jig is aligned when the front is aligned. When the jaws are closed the back end pieces need to be perfectly aligned. If this is done, the next thing is to drive a flat head screw into that back end that also holds the side of the wooden jaw that you glued on.
When all these are done, the jig is complete and ready to use.
Using the Kerfmaker - Make a Test Cut FIRST
The first thing to do before using the jig is to align the screw with the thickness of your saw blade. This is easy to do with a screwdriver. If you want your dado to have a snug fit, the screw head should be slightly more than the thickness of your saw blade.
Next, take a measurement on a piece of wood you want to make a dado for. You need to be accurate so make sure the inside jaws are set to exactly the size of the wood and locke the 2 jig sides together with the wing nut.
The Kerfmaker always needs to align with something and that something needs to be narrow enough to accommodate the inside of the Kerfmaker where that flat head screw is.
Attaching a small block of wood to your fence with a clamp will often work just fine.
To set the dado distance, align the widest part of the jig, first of all, make a cut, then the narrowest part, the one with the flat head screw, make that cut, then carefully nibble out the wood between the 2 cuts and test your joint. If all the steps were followed you should have a perfect dado cut or at least close, you may still need to adjust the flat head screw, but that should put you well on your way to perfect dados ..
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