How to Measure Angled Cuts in Woodworking
Most woodworking is all about cutting square. But to really up your game in the shop, you have to know how to cut angles in wood. Picture frames, mitered boxes, chairs, or even something as simple as this display shelf, which involves all non-90-degree cuts. But how do you determine the necessary carpentry angles? How do you lay them out? How do you use a protractor for woodworking? And how do you set up your machines to cut them accurately? Tools for how to measure angled cuts in woodworking typically perform one or both of two functions: registering an angle, and identifying it. For example the time-honored T-bevel registers a woodworking angle by conforming to its shape. Then a protractor is used to identify the angle in terms of degrees.
Although those two tools used in conjunction may satisfy the majority of your woodworking cutting angles, manufacturers offer a plethora of options. As I’ll show you in this article, some efficiently register and identify cutting angles in wood in one operation. Some are better for large layouts. Some take innovative, high-tech approaches to faster, more accurate machine setups. Read on to discover how to determine angle of cut and the best ways to complement your spot-on measuring and marking.
T-bevel and Protractor for Woodworking, Hand in Hand
The T-bevel, also called a sliding T-bevel or even a bevel square, is the time-tested first choice for gauging and transferring woodworking angles. This tool consists of a thick handle that locks around a thinner blade. Available in lengths from 4" to 14", but an 8" to 10" model is ideal for most furniture work. It’s perfect for laying out hand-cut dovetails, like in this narrow display cabinet. To get the most from a T-bevel, pair it with a protractor to determine an angle’s measure. In practice, a protractor for woodworking with a bigger scale means more accuracy and easier visibility—something to factor into your purchasing decision.
Fast miters
To quickly set your T-bevel to 45°, register it against a precise combination square such as one made by Starrett. For more information on cutting accurate carpentry angles, check out Family Handyman’s 14 Expert Tips for Tight Miters.
Woodworking cutting angles galore
At 0°-60°, Veritas bevel setter has a wider range than the I-Gaging model, although it’s smaller and only divides each degree in half. Its reverse side is etched with some of the more commonly used woodworking angles. The vintage Stanley T- bevel locks the blade securely with a knurled knob at the end of its handle.
Back to math class
The two protractors shown here might remind you of math class. The model lying on the bench is similar to this Shinwa model, which has easy-to-read markings from 0°-180°. The two-sided Sawset protractor for woodworking features a cutaway section for your T-bevel. One side is calibrated for the actual angular measure while the obverse side (inset) notes the bisected angle as reference for setting your saw to cut a miter joint.
To test your angle-finding skills, check out this free flatware caddy project.
Beyond the T
While you can’t go wrong with adding a T-bevel (or two) and a protractor to your tool arsenal, alternatives abound. The tools shown here work similarly, but have their own unique features for how to measure angled cuts in woodworking. Now, we’re getting into bevel basics and beyond.
All in one tools for cutting angles in wood
For the minimalist woodworker, a handy multi-tool from Lee Valley might be all you need in your apron pocket. In addition to serving as an excellent T-bevel, it also functions as a square, marking gauge, depth gauge, compass, divider, and 12" rule. You’ll still need a protractor for measuring and setting specific woodworking cutting angles.
Combo square add-on
Available as part of a set, or as an added accessory, a protractor head that slides on the blade of your 12" combination square is great for how to determine angle of cut. This cast iron head from PEC Tools fits perfectly on a Starrett rule. The protractor is graduated from 0°-180° and from 180°-0°, though the etched numbers can be hard to read. Use as shown, or slide your T-bevel through the protractor’s slot to transfer the carpentry angles.
Digital angles
This plastic/metal digital T-bevel from General features a small but readable LCD screen that indicates woodworking angles to the 20th of a degree, eliminating the need for a protractor. It is sensitive enough that setting specific angles takes a steady hand.
Bigger Tools for Bigger Woodworking Angles
When it comes to how to measure angled cuts in woodworking, an 8" to 10" T-bevel will suffice for most furniture work. But when laying out angles on plywood and other sheet goods, it helps to have longer tools. Some of the tools that follow are bigger cousins of those discussed above, while others are unique to the tasks involved.
Long and low-tech
Long and high-tech
Carpentry angles
Sold as a T-square for drywallers, this large, aluminum layout tool from Kapro has several key features that make it useful for plywood layout. Its sliding head has detents that lock it in place at 90°. But by loosening the knob you can readily pivot the head to any desired angle. It also has a built-in protractor with a few common woodworking cutting angles, such as 30°, 45°, and 60°. The head also folds parallel to the blade for compact storage.
Is it 90° or is it 0°?
One confusing aspect of setting up tools for cutting angles in wood involves the gauge on the machine itself. Most table saws, miter saws, and many quality miter gauges, such as this one from JessEm include a scale that begins at 0°, indicating it is set to make a 90° (or square) cut. Then as you tilt the blade (on a table saw) or pivot it (on a miter saw) the pointer will register somewhere between 0° and 45°. The I-Gaging and Veritas protractors correspond with this system, but other protractors (and many woodworking plans) refer to a square cut as 90° rather than 0°.
To compensate for this discrepancy, recall a lesson from geometry class on complementary angles (No, you won’t have to do a proof!). Complementary angles are two angles that, together, equal 90°. So, if your plans call for a 70° cut, you’ll use 20° on your machine’s scale (70° + 20° = 90°). Also, understand that the angle scale on the front of most table saws only gets you in the ballpark. For precise woodworking angles, you’ll need a T-bevel and protractor, a digital angle gauge, a set-up block, or even a drafting triangle. This Old House also has a list of 10 angle measuring tools that will help with your day-to-day woodworking.
Cutting Angles in Wood With Machines
Knowing how to determine angle of cut is only half the battle. You also need to transfer those angles to your machinery for accurate work. Some of the tools featured in this article excel at both layout and machine set up. But a couple of dedicated tools make set-ups quick and painless.
Raise and conquer
To tilt the blade on your table saw to a specific carpentry angle, raise the blade to its full height. Then set your T-bevel to the desired angle, and tilt the saw blade until it parallels the T-bevel blade. Be sure the tool handle is flat on the table and aligned with the saw’s arbor, and that its blade extends between the saw blade’s teeth. Lock the saw’s tilt control, and lower the blade to a safe height for the operation.
Building accurate jigs is another way to conquer complex angles, like the ones found in this Schoolhouse Regulator Clock.
Making miters
Magnets and technology for woodworking cutting angles
