Best Combination Squares for Woodworking
A combination square is the tool everything else gets measured against, which means it has to be right. The good news is that a square is either accurate or it is not, and you can check it in about twenty seconds with a pencil and a scrap of wood.
How to check whether a square is actually square
This takes one scrap of wood and takes seconds:
- Find a board with one straight factory edge.
- Butt the square's head against that edge and draw a line along the blade.
- Flip the square over so the head is on the other side of the blade, line the blade up with the line you just drew, and draw again.
- If the two lines are parallel, the square is true. If they splay apart, it is out by half the angle between them, and you can see it immediately.
Do this with any new square before you trust it, and repeat it occasionally, because a square that has been dropped can go out without any visible damage.
What the parts are for
- The 90 degree face. Marking square lines across a board and checking edges.
- The 45 degree face. Marking miters and checking them. More useful than it first appears.
- The sliding blade. Used as a depth gauge, a marking gauge, and for stepping off repeated measurements by locking the head at a set distance.
- The bubble level. Handy but rarely the reason to buy one.
- The scriber. A small pointed pin stored in the head, for marking on metal. Most woodworkers lose it.
What size to buy
| Blade | Best for |
|---|---|
| 6 inch | Shirts pocket, small joinery, quick checks |
| 12 inch | General purpose, the size most people should own |
| 16 inch | Cabinets, sheet goods, longer square lines |
A 12 inch is the default. A 6 inch earns its place because it is the one you will actually carry to the saw rather than walk across the shop for.
Combination square versus the alternatives
- Try square. Fixed blade, wood or steel handle. More precise for marking joinery because there is no sliding head to introduce play, but less versatile.
- Speed square. Triangular, for framing and rafter work. Not a precision tool, indispensable for framing.
- Bevel gauge. Transfers an existing angle. Different job entirely.
Frequently asked questions
Is an expensive square worth it?
Up to a point. A mid-price machined square from a known brand is usually accurate and holds up. Beyond that you are paying for finish and branding, not for accuracy. What you should not do is buy the very cheapest one and assume it is square: check it, because a meaningful number of them are not.
Why does my square rock on the board?
Either the head is not seated flat against the edge, or there is a burr or debris on the blade. Clean the blade and make sure the head is fully against the reference edge, not riding on a rounded corner.
Can I use it as a marking gauge?
Yes. Set the blade to the distance you need and lock it, then slide the head along the edge while the blade end scribes the line. It is slower than a real marking gauge but it works, and it is one of the reasons a combination square is worth owning.
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