Wedges (and shims, which are just thin wedges) are used for many purposes. They hold the handles on axes, picks, and hammers, They are used to adjust and hold window and door frames in place while they are permanently fastened. They can be used to level cabinets, tables, washing machines, or ladders. Thicker wedges are used to stop doors from swinging or cars from rolling. They can be used to assist in splitting firewood. Two opposing wedges of the same angle keep their sides parallel while changing the distance of the parallel sides.
Cutting wedges without a jig tends to be inaccurate and can be dangerous because you're working with rather small pieces of wood close to the blade of the saw. The jig that I want to show in this Instructable cuts accurate shims and wedges on a table saw safely, repeatedly and dependably.. It is used for making wedges and shims from scrap wood like 2x4's
After having made several shim-cutting jigs, I have come up with a very simple-to-make jig. I've made several other versions, but they were all much harder to make, took much longer, and didn't work any better.
Step 1: Materials:
If you have a table saw, the only things you really need to make your own shim-cutting jig is some scraps that are about the same length as the shims you want to cut, generally somewhere between 6" and 10". It's a good idea to use the same thickness of wood for the jig that you are going to use as material for your shims/wedges. Often you want to cut shims that are fairly wide, so 2x4 stock for both the jig and wedges works pretty well. If you want them to hold the handles on tools, you may just want 1" to 3" long wedges out of 3/4" thick stock. This Instructable shows the technique using scrap 2x4 construction lumber. Larger or smaller, thicker or thinner ones can be quickly and easily made as needed once you understand how this works.
Step 2: What Size Shim Do You Want?
The first thing is to figure out what size shim you want to make. You may want copies of a shim that you have. Or it can be based on the shim thickness and length you need or you may need a specific angle of wedge. A 5 degree angle will give you a shim that's about 1/2" thick and about 6" long, which is a pretty handy size. If you only want shims 1/4" thick, you either have to make them shorter or use a smaller angle. An 8" long, 2 degree shim will be just over 1/4" thick at the thickest part which is just about what they sell at the stores for window, door and cabinet installation, but for illustration purposes, I'll make a 5 degree, 6" jig. This will also let you make longer shims that are proportionately thicker (a 10" shim would be 7/8" thick)
You could make a jig like this for any angle, but angles more than 45 degrees are easier cut with your crosscut miter gauge or a miter saw. This is primarily for thin wedges and shims.
If you are mathematically inclined - or have a scientific calculator - the tangent of the angle times the length of the shim will give you the thickness. (Or the thickness of the wedge divided by the length equals the tangent of the angle - it depends on which way you want to figure it.)
Step 3: Making the Jig:
If you are trying to duplicate a wedge or shim that you already have, you can substitute the screw with that wedge. Fasten it with brads or even just tape it on with duct tape.
If you don't have a shim to copy, take a piece of scrap wood that's about the same length as the wedges you want to cut and drive a screw into the side near one end. I used a 7" piece of 2 x 4. How long a screw you need depends on how thick a wedge you want. Thicker wedges need a longer screw.
Place the jig piece (the one you want to cut at an angle) with one end resting on the screw head and the other against another scrap piece placed against your rip fence (to save your rip fence from being scratched by the screw head). Adjust the screw in or out to give you the angle you want. Once you have the correct angle, set your rip fence for the narrowest end of the assembly (the block with the screw in it and the scrap piece) along the rip fence as shown. Use push sticks to push the whole thing (scrap and jig piece together) through your table saw. You can see it the picture how this will cut an angle off the block that will become your jig. (Guards were removed from the table saw to make everything easier to see and understand.) Now take the screw out. You don't need it anymore.
The jig piece now needs a tab to catch one corner of the wood you're going to make the wedges out of. This is just a small piece of wood or stiff plastic fastened to the narrow end of the jig to keep the wood you're making the wedges out of from moving around while you're cutting it. I like using plastic because it' doesn't split. (I cut this one out of a pants hanger and also got 2 "chip clips" out of it) Drill and countersink this tab and screw it to the narrow end of the jig body so that it sticks out just enough to catch and hold a block of wood (maybe 1/4"). This makes a pocket that the back corner of the shim stock will fit into.
I screwed a scrap of 3/4" plywood across the top to keep the stock piece from being pushed up by the saw blade during the cutting operation. This piece will have a cut in it after the first use - it's a disposable piece. While it isn't really necessary, it makes cutting shims safer.
I also prefer to put a handle on most of my jigs to keep my fingers away from the saw blade. I like using what I call "modular" handles because they can easily be installed and removed from different jigs and they allow the jigs themselves to take up less storage space. I show how to make several different ones at https://www.instructables.com/id/Modular-Jig-Handles/. The nice thing about modular handles is that you only need one or two instead of needing one for every jig you have. To attach one to a jig just requires 2 screws to be installed, then the handle locks onto those screws. The handle can be removed quickly and easily for storage or for use on another jig. Whether you use my method or even put a handle on yours is up to you - they're your fingers, but I certainly recommend it.
Step 4: Using the Jig:
Place a piece of the material you want to make your shims out of (your shim stock) in the pocket as shown and set the distance from the blade to the rip fence so that there's just a tiny bit of the shim stock over the blade. The first picture above is from the outfeed side of the table saw, but it shows how to set the rip fence. If you want a super-thin point on your wedge, you can set it to exactly the width of your jig but that will make the point so thin that it tends to break very easily. Set the height of your saw blade to slightly higher than your stock is thick. The second picture above shows the setup from the working side. Holding the shim stock against the jig (but not so tightly that you pinch the saw blade, especially as you're nearing the end of the cut) and the jig against the rip fence, push both the jig and the block through your saw. You now have your first shim and a block with one end narrower than the other. Remove the shim and set it aside. Now flip your stock piece over, end-for-end, so that the narrower end is towards the saw blade, and put the wide-end corner nearest you into the pocket of the jig. Pass the assembly through the saw again. You'll wind up with another shim and a block that again has parallel sides. Repeat this process until the block you're cutting from becomes too small to continue safely. I can easily get six 1/2" thick shims out of a scrap 2x4. Out of a 2x6, I can generally get ten. If you ask at construction sites, they're generally happy to give you all the cut-off ends of lumber you want, giving you lots of material for all the wedges you'll ever need.
Step 5: Conclusion:
This is an accurate, easy and safe way to cut small angles on a table saw. You can use a similar method to cut all sorts of thin wedges off your stock. You can even use a larger, longer one to cut the taper on legs for furniture as this is just a backwards version of a commercial taper jig. I will show in a future Instructable how to make and use a similar, related jig to cut the legs of a cheap, versatile saw horse. You'll find lots of uses for various sizes of wedges (like locking jigs into slots on your saw table). I actually held a temporary door frame in place for several months with a few wedges - literally "wedging" it in place.