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Learning how to capture, transfer, and measure angles is a foundational woodworking skill. It’s required knowledge when building many carpentry projects, but furniture makers and fine woodworkers will find it helpful, as well. Nowadays, we rely on our miter saw, bandsaw, or circular saw to line up and cut specific angles, but first, we need to be able to find, measure, and mark those angles with a speed square and a bevel gauge – a skill that’s easy to learn.
How to use a speed square
The speed square is first-and-foremost a 90 degree right triangle. It has a “shoe” at the bottom that holds the edge while you strike your lines. One side is slanted at a perfect 45 degree angle and allows you to strike a quick 45 degree line.
The speed square can also be used as a protractor and this is one thing that makes it stand out from a normal try square. By positioning the corner marked “pivot” at a specific point, rotate the square until the desired measurement mark lines up with the edge of the wood. This gives you an angle in reference to the vertical 90 degree side of the speed square.
For carpenters, the speed square will also measure common rafter pitches. These measurements are required for framing, but won’t be used in furniture making or any other woodworking projects.
There is a rule on one side of the square and the length will depend on the length of square you buy. The one shown here is a 7 inch square and the rule is about 7 1/8 inches long. This size allows marking across two 2X4s at the same time.
Lastly, there are brands that have notches on the inside triangle to allow for easy scribing. This square doesn’t have that feature so I hold the pencil steady at the desired measurement and I’m able to scribe a line parallel to the edge by sliding the square. Be sure to keep it registered against the edge.
How to use a bevel gauge
The bevel gauge is a tool that doesn’t get much attention in today’s DIY culture. I think that’s probably because the current popular styles include straight lines and simple joinery. It can be useful in hand tool woodworking (marking dovetails), boat building, construction carpentry, and cabinetry.
There are two movements to a traditional sliding bevel gauge. The first is rotation to capture an angle and it will also slide along a slot to measure the length of an angle. Once the gauge is setup the nut can be tightened to maintain the setup.
Transfer an angle from the wall to a workpiece
The first situation we’ll look at is to transfer the angle from a wall to your stock. I’m working on custom built-ins and the space I’m building them for has a fairly steep angle. I put the gauge up against the wall and rotated the blade until it was flush with the pitch of the ceiling. I then transferred the angle to my cabinet side. It’s a very simple and easy process.
Measuring an angle
Let’s say we needed to know the angle measurement for some reason. By using the protractor feature of the speed square that I mentioned earlier, we can quickly place the pivot point at the beginning of the angled line. Then, rotate the square until its side is even with the angled line. The mark inline with the edge of our board is the angle measurement. In this case, 35 degrees.
Marking and cutting a miter angle
Often, plans will call for a particular miter angle to be cut into the end of a board. There are a couple of easy ways to do this based off of what we’ve learned.
We can take the speed square and use the protractor feature right on the end of the board. This is the easiest and quickest way.
But, if you have several cuts to mark and cut, of this same angle, it’s more accurate to use the bevel gauge. First, use the speed square to mark the correct angle. Then, set the bevel gauge to the bottom angle and transfer it to the work piece.
Important: Miter cuts are labeled according to the angle that is cut away. So, a 40 degree miter means you cut away the 40 degree angle and left the 50 degree angle.
Finding an angle that is inaccessible
Suppose you need to find the angle of a work piece that is attached and inaccessible.
First, use the bevel gauge to capture the outside angle of the work piece.
Transfer the angle captured to a work piece with the bevel gauge.
Use the speed square to measure the angle as described before.
It may seem unintuitive that this angle is the actual measurement we’re looking for. It makes more sense if we understand that the angle is in reference to the end of the work piece being flat or 90 degrees. You can see that the end resembles what we’ve drawn and measured.
Now you’ve got a basic understanding of how to use a speed square and bevel gauge, so get out in the shop and put them to work!
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