A simple guide for beginners to learn how to use a Speed Square or carpenter’s square in woodworking. Learn about all the features and uses!
A Speed Square or carpenter’s square is one of the most basic and essential tools in woodworking. It is extremely inexpensive, accurate, and has a wide variety of uses!
You often see the Speed Square being used as a way to make sure everything is perpendicular and square while building. That is just a scratch on the surface of everything that tool is capable of!
As a beginner, it can be overwhelming looking at the wide variety of markings!
Today I am breaking it down for you in detail to show you exactly what everything means AND how to use it so you can put that triangular tool work!
Table of Contents
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What is a Speed Square
A Speed Square is a triangular carpenter’s tool. It is also commonly known as a rafter square or a carpenter’s square. The term “Speed Square” is trademarked by Swanson Tool Co., Inc. but is commonly used as a generic name.
If you are in the market to buy a carpenter’s square, I would highly recommend getting the Swanson Speed Square. It is jam-packed with all the features which might be missing in other brands!
What can you do with a Speed Square?
The main purpose of the Speed Square is to layout lines very quickly and accurately. However, you can also find and draw angles and circles, adjust or guide a saw, and even use it as a level!
Before we get into details of how to do all this, let’s get to know the Speed Square and talk about all its uses.
Features of the Speed Square
A Speed Square is packed with features that make for uses well beyond the most obvious one – using it as a way to square boards. Below are the basic features which are most relevant to woodworking.
Along one of the outside edges, there are markings from 1 through 6. This is the ruler side. It’s useful for quick measurements. It is limited to six inches so you can only use it for smaller measurements but it can be a quick reference when working with it.
The t-shaped edge is probably the most used feature of a Speed Square. It can be bumped up against one edge of a board, and you can scribe a straight line with a pencil. Plus, you also guide a saw blade with it!
3. Right Angle
The most obvious use of the Speed Square is to use it at the right angle. The 90-degree angle is easy to use without needing a protractor. You can trace around it, use it to confirm cuts, and even check your assembly for perfect corners quickly. The most important use – check your saws to make sure the blade is square.
The side opposite the right angle is marked with lines and the numbers 10 to 80 or 0 to 90 – depending on your speed square’s manufacturer. This side is how you can use your Speed Square for angles. I will go into detail about how to use it to measure or mark angles below.
5. Diamond-Shaped Hole
This hole is 3½ inches from the end and makes for a helpful quick measurement since the width of two-by-fours is actually 3½ inches, not 4 inches.
How to use a Speed Square
The above list makes it clear that the Speed Square can be used in so many ways! Now let’s dive into exactly how to use it for each purpose.
1. Check for square
As the name suggests and the first thing that probably comes to mind – a speed square can be used for quickly checking for square between workpieces.
Also, it is great to check if the ends of a board are square.
Below, I am checking to make sure that the mitered joint is perfectly square.
2. Use as a Saw Guide
A Speed Square make s a quick and accurate fence when using a circular saw to cut boards.
- Hook the t-shaped lip on the outer edge of the board.
- Line up the shoe of the saw against the straight edge parallel to the cut.
- Make the cut!
3. Adjust Saws
One of the most important parts of building professional quality furniture is to make sure all your pieces are cut perfectly square. Hence, it is important to ensure that the saw blades are “square” – which means they are perfectly 90-degrees to the plane on which you place your boards.
For example, to adjust a circular saw – rest one side of the Speed Square against the side of the blade. Rest the against the bottom of the saw. Both the sides should line up with no gap. If there is a gap, adjust the blade till it disappears.
4. Measuring Angles with a Speed Square
Measuring and marking angles with a Speed Square make it so much easier to ensure that the mitered cross-cuts are perfect! The right angle and the 45-deg angles are easy to see! Here is how you use it to measure or mark any angle you want –
- Line up the lip of the Speed Square with the edge of the board so the pivot point is at the starting point of the cut.
- Pivot away in the direction of the angle you need until that specific angle (in our case below – it is 30-degrees) marking lines up with the edge of the board.
- Draw the line along the edge. This is the angled line!
Below is my TikTok video showing you measuring angles in action –
A similar technique can also be used to measure an angle.
5. Drawing Circles with a Speed Square
Yes, you can use a speed square to make circles!
I think it is the easiest to make these using the Swanson Speed Square because it has the notches for the markings. You can use the outer edge to make circles up to 12 inches, although, it might be a bit tricky.
- Place a nail or screw at the pivot for the speed square to rotate
- The notch in the speed square at the pivot point can be hooked on to the nail.
- On the ruler side of the speed square – place a pencil at the radius of the circle you need.
- Walk the speed square around as you rotate the speed square around.
That will help make a simple circle.
6. How to mark boards for ripping
If you need to draw a straight line across a board to rip it down, it is super simple to do so with a Speed Square!
- Place the Speed Square with the t-edge over the edge.
- Place a pencil on the measurement mark on the ruler side.
- Slide the speed square down the length of the board and draw a line with the pencil as you go.
Tip – Be sure to use a sharp pencil (not a carpenter’s pencil) for this. Many speed squares feature a sawtooth along the ruler edge that is very helpful.
Use a Speed Square for leveling is a little more complicated than using a level but it can be done in a pinch. You’ll need a plumb bob or a string and nut.
- Place the square on the material with the pivot point facing up.
- Then take the plumb bob or string and nut and lay it across the speed square.
- If it is level, the string will rest on the 45-degree mark. If not, you’ll know precisely how unlevel the item is.
Finding Roof Pitch
While you may not use a speed square for roofing, it can be used. This is a good article to understand how it works to find the roof pitch.
So there you have it.
SO MANY things you can do with that simple triangular tool! Let me know which of these was new to you!
More Beginner Woodworker Articles –
Check out the Woodworking 101 hub for lots more beginner-friendly information, articles and project ideas.