Mitre Saw Not Cutting Square? How to Calibrate It Properly

Your mitre saw says it's set to zero degrees but your cuts aren't square. The skirting doesn't meet properly, your picture frames have gaps, and you're burning through timber trying to get mitres to close up. Here's how to actually fix it.

First: Check If It's Really the Saw

Before you start adjusting anything, grab a known-good engineer's square (not a cheap speed square) and check your reference.

Cut a piece of scrap timber with the saw set to 0 degrees. Hold your square against the cut face. Can you see daylight between the square and the timber? If yes, the saw needs calibrating. If no, your problem might be the timber itself - twisted or cupped boards cut square but don't sit flat.

Checking and Adjusting the Fence

The fence needs to be dead square to the blade. This is the most common issue.

1. Unplug the saw (obvious but important)
2. Lower the blade fully without starting it
3. Hold your square against the blade body (not the teeth) and the fence
4. Look for gaps

If there's a gap, the fence needs adjusting. Most saws have bolts holding the fence that allow for micro-adjustment. Loosen them slightly, tap the fence into position, retighten, and check again. This might take a few attempts.

The Blade Itself

A warped blade will never cut square no matter how well the saw is set up. Hold a straight edge against the blade body. If it rocks or shows gaps, the blade is bent. Replace it.

Cheap blades warp more easily, especially if they've overheated. A decent blade from a proper brand isn't much money but makes a big difference. Check out our saw blade selection.

Checking the 0-Degree Stop

Most mitre saws have an adjustable stop for the 0-degree position. Over time and through knocks, this can shift.

With your square confirmed against the blade and fence, check that the angle indicator actually reads 0. If the cut is square but the indicator doesn't say 0, adjust the stop - there's usually a small bolt or grub screw.

The Bevel Angle

Don't forget the bevel (the tilt left to right). If this isn't at true 0 degrees vertical, your cuts will be angled across their thickness even if the mitre is correct.

Use your square against the blade and the table surface. There's usually a 0-degree bevel stop that can be adjusted similarly to the mitre stop.

Table Flatness

If the table itself is dented or warped (common on older or cheaper saws), timber won't sit flat and cuts won't be consistent.

Place a straight edge across the table in several positions. Any high or low spots will affect your cuts. A damaged table usually means replacement or living with the limitation.

Extension Wings and Supports

If your extension wings aren't level with the main table, long pieces won't sit flat. Check these are properly aligned - most can be adjusted with the mounting bolts.

After Adjustments: Test Cuts

Once you've made adjustments, do test cuts to confirm:

1. Square cut at 0 degrees - hold square to cut face
2. 45-degree mitre - cut two pieces, they should form 90 degrees when joined
3. Bevel cut - should match your square held vertical

When It's Time for a New Saw

If you've calibrated everything and still can't get consistent accuracy, the saw might be worn out. Bearings wear, slides develop play, and adjustments reach their limits. A saw that's given you years of service might just be done.

Good mitre saws from DeWalt and Makita hold their calibration well and have proper adjustment systems. Budget saws often lack the fine adjustment needed for precision work.