Using a set square on wax

Bench peg with a set square on it

Measure flatness

The first thing you want to use a set square for is to check if something is flat. A set square has a thick and a thin arm. The thick arm is a bit more forgiving in your measurement, but it’s easier to see gaps from the thin arm. That's why I always use the thin arm for measuring.

It’s pretty easy, you just put your wax against the arm and check if there are any gaps.

Close up of hands holding a set square and measuring a blue piece of wax against the thin arm. There are several gaps visible

Make sure you’re looking at it straight on. If you angle the set square, anything can look flat!

Close up of hands holding a set square and measuring a blue piece of wax against the thin arm. There are no gaps visible

That's the same piece seen from a lower angle. It looks flat now, but it still has the same amount of gaps!

It’s easy enough to see the big gaps. But smaller gaps can be more difficult to spot.

Close up of hands holding a set square and measuring a blue piece of wax against the thin arm. There are several gaps visible. A red arrow points to a very small gap that is not as easily visible

I like to hold the set square to my window when I’m checking the flatness. With plenty of light, you can see the smallest of gaps.

As long as you can see gaps, your piece is not flat yet. You have to keep filing and checking until the entire length of your piece is touching the arm of the set square.

Close up of hands holding a set square and measuring a blue piece of wax against the thin arm. There are no gaps visible

And when it’s touching completely, you know it’s perfectly flat!

Measure 90° corner

Once you have a flat side, you can use the set square to make 90° corners.

Use the fat arm of your set square as the guide and place the side of the wax you know is flat against it.

Close up of hands holding a set square and measuring a blue piece of wax against the thick arm. There are no gaps visible

Then push it all the way up to the thin arm.

Close up of hands holding a set square and measuring a blue piece of wax in the corner. There is a gap visible on the top

To measure accurately you have to make sure you hold your flat side firmly against the arm of the set square.

Close up of hands holding a set square and measuring a blue piece of wax in the corner. A red arrow points to the side that is completely touching the arm of the set square

If you angle it away from the set square you won’t get an accurate measurement.

Close up of hands holding a set square and measuring a blue piece of wax in the corner. A red arrow points to the place where I'm angling the wax away from the set square.

As long as there is a gap you don’t have a 90° corner yet. You have to keep filing and checking until both sides touch the arm of the set square perfectly.

Close up of hands holding a set square and measuring a blue piece of wax in the corner. Both sides are touching

Congratulations! Making a 90° corner is hard work!

Measure your whole piece

You’ve filed and measured, measured and filed, and you finally have your 90° corner...in one place. When you’re working with a thicker piece of wax, you have to make sure that you measure the entire surface and not just one point!

You can have a perfect 90° in one place of a piece

Close up of hands holding a set square and measuring a blue piece of wax in the corner. Both sides are touching

but in another place, there can still be gaps!

Close up of hands holding a set square and measuring a blue piece of wax in the corner. There is a gap visible on the top

If the piece you’re measuring is thicker than the arm of the set square, you have to move your piece on the set square in order to measure the whole surface. You want the entire piece to be 90° and not just the first few milimeters.

If you’re finding this bit hard to understand, just measure a ring! Your ring can have a perfectly flat profile in one place.

Close up of hands holding a set square and measuring a turquoise ring. No gaps visible

And it can be completely off in the next place.

Close up of hands holding a set square and measuring a turquoise ring. Gaps visible

Other corners

A set square is made to measure 90°, but you can use it to check other angles as well. As long as your piece has one flat side you can place on the fat arm, you can use the set square to check the evenness of any corner, angle or curve.

Close up of hands holding a set square and measuring a turquoise court shape ring

Just pay attention to the shape of the gap in the corner.

Close up of hands holding a set square and measuring a turquoise court shape ring. A red arrow points to the gap that you need to look at

When you move your piece on the set square, you want the shape of the gap to stay the same. If the shape of the gap changes, I know there is an unevenness in my curve!

Ruler

After all the precision work, you’ll be happy to read you can use the set square for simple things as well. Like marking straight lines!

Just place the wax that you want to mark against the thin arm and use a scribe to mark a line.

Close up of hands holding a set square with a block of wax held against it. Right hand is marking a straight line on the wax, using the side of the set square as a ruler

See! Easy!

Comment below and let me know if these tips were helpful!