I have a very specific way of cutting box miters. And it helps me overcome one of the trickiest parts of this joinery style.

The essence of the miter joint is a 45° cut. Just angle your table saw blade, set up the board on your crosscut sled, and push it through.

Seems simple enough.

But here’s the problem.

When your blade is angled, it gets really tricky to line things up accurately. Especially when you’re building a box that needs sides of exact lengths.

Luckily, this 2-step system makes it easy to make miter box sides of precise dimensions — and it’s super easy to follow..

Here’s how it works.

For the first step, completely ignore the fact that these will be miter joints.

That’s right.

You’re going to cut your box sides to their final length with a boring old 90° crosscut.

It’s a lot easier to accurately mark a 90° layout line in the edge of a board than a 45° line.

And you can use that line to click into the table saw blade’s teeth for a supremely on-the-money cut (here’s a refresher on how).

Also, make sure to use a stop block. There’s no better way to ensure two different boards are cut to the exact same length.

Now all your board sides are cut to length — but we’re not making a butt joint box. Have some self respect (totally kidding… there’s a chair for every butt joint).

So here we move on to making these butt joints into miter joints.

For these cuts, I like to use my 1-sided crosscut sled.

But the real trick is cutting a new zero-clearance guide kerf.

This is a sacrificial board you attach to the face of your crosscut sled’s fence (use screws, clamps, whatever works).

After setting the blade to 45°, push the sled through the blade to cut a fresh kerf in the auxiliary fence.

Since “45°” setups can sometimes differ slightly, this fresh kerf will show you the EXACT edge of the cut. Which makes setting up your boards a cinch.

Place one of your boards on the sled and position it so the top end grain corner just barely touches the edge of the kerf.

The goal is to position it so the length of the top face doesn’t change at all — you’re simply cutting away the material below.

Once it’s set, lock down your stop block to keep it stable and make the cut.

(If you’re a little unsure, you can also sneak up on this cut. The micro-adjust feature on the Katz-Moses Stop Block makes it easy).

Repeat this process for all the other boards, and voila. You’ve got perfectly sized sides for your miter joint box.

Want more tips for cutting accurate miter joints? Read this.

Do you have another system for making sure miter box sides are the right length? Share it with us in the comments below!

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