How To Use A Speed Square

The smell of sawdust (I mean man glitter), the perfectly-measured cut secured by a brilliant pocket hole, these are some of my favorite things. The art of carpentry has levels, admittingly, I'm a hobbyist but love it nonetheless. Regardless of their skill level, every craftsman needs a speed square in his tool chest.

You likely have one hanging neatly on your pegboard above your tool bench, but do you know all the uncommon yet game-changing ways to use it? This guide will equip you with 7 helpful ways to use your speed square, from drawing a perfect circle, tracing a rip cut, or measuring and scribing an angled cut. 

What Is A Speed Square?

Let's slow down for a second, and briefly discuss what the speed square is. Originally known as a "rafter square" as it's a versatile carpentry tool used to mark angles and measure cuts on lumber. The name "speed square" isn't referring to how fast the tool is, but more so how much time it can save in quickly marking precise measurements quickly on the job site. It's a triangle in shape with various numbers etched into its frame brought together by a lip to slide along the edge of a board.

The old adage "measure twice, cut once" was likely written by a man who knew his way around a speed square. It's likely the most unappreciated tool that exists, let's discuss all the pivotal (pun intended) ways that you can utilize this triangle.

1. Scribing Circles

If you thought I would pivot and start this guide off with how to use your speed square to make a perfect circle, you hit the nail on the head! To scribe a circle with your speed square, grab a nail, hammer it part-way into the wood where you want the circle centered, and you've created a pivot point to use your speed square to scribe a perfect circle. You can select the size of the select by adjusting which slot you place your pencil.

2. Scribing Angles

Even if you're not the smartest tool in the shed, you likely know how to use your speed square to scribe a perfect 90° or 45° line, or have used it as a guide to ensure something is flush. But did you know those numbers on the long edge are for measuring degrees? And that little notch next to the lip is for pivoting to measure them? 

Essentially you've always known you could measure and scribe angles using a speed square, but the only angles you used were 90° and 45°. Here's how to measure the other angles.

• Place your speed square flush on the bottom of a board, and scribe a vertical line.
• Holding the pivot point to the board, slowly lower the other edge.
• The number on the left (below) indicates the angle.
• As you move the speed square, the degrees, angles, grow larger.

IMPORTANT: The angle measured is not the left side pictured below, it is the angle connected to the vertical line you scribed.

Pro tip: you can also use this to measure pre-existing angles.

3. Marking Rip cuts

You may find yourself staring at a piece of wood wondering how you are going to cut it with the saws you currently have. You just got back from your 3rd trip to Home Depot today and you aren't going back to have them make a long cut for you. You need to scribe and make a rip cut on a long board. Here's how your speed square will help:

• Place your speed square flush on the bottom of a board.
• Place your pencil in the notch accordingly
• Slowly move your square guiding the pencil

This can be especially helpful when the board you bought from Home Depot is as warped as a hockey stick, you may be able to salvage it with a rip cut. 

4. Guide Saw Cuts

Especially on job sites, you may not have the perfect saw close by for the cut you need to make. Grab your speed square and circular saw. Fun fact, your speed square was made 7 1/8th inches for a reason, 2x4's are 3.5inches and you can carefully cut up to two of them at once using your handy speed square as a guide:

• Always mark your cut before you make it with a pencil.
• Place the board or boards on a flat surface flush together.
• Place your hand safely on the side opposite the saw holding the lip of the square.
• Use your speed square as a guide to your circular saw as it cuts.

5. Finding Roof Pitch

This is where the name "rafter square" comes into play, and the real professional carpenters enter the conversation. You can use the numbers below to measure hip and valley cuts when building rafters. For a more in-depth guide, you can check out this video where he covers it more extensively. 

6. Spacing

This may be my favorite use of the speed square, and it's definitely the easiest to incorporate into your wood working routine. The lip on your speed square is 3/16's inches thick, which just so happens to be a great consistent gap between deck-boards. Deck-boards, or other boards need gaps for moisture. Keep in mind, unless it's manufactured wood, it likely isn't perfect so you'll need a square or similar spacer every couple of feet.

7. Remember Measurements

This is so simple I can't believe I never thought of this. How many times do you walk from your tool bench to your project and forget the measurement you had in your head? (Mdrive makes a killer powder that supports brain health and memory, try it for only $1 a day.) 

Conclusion

Whether you're a pro with years of experience or just getting started in the wonderful world of woodworking, a speed square is a jack-of-all-trades tool that hopefully now you know how to use right. From scribing perfect circles to guiding rip cuts and even acting as a spacer between deck-boards, this triangle-shaped wonder has got your back.

If you were stuck in the rut of only using it for simple 90° and 45° angles, I hope this guide opened up a whole new world for you. Remember, it's not just about having the right tools; it's about knowing how to use them to their full potential. So next time you're in your workshop, give these tips a go and up your carpentry game.

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