Recalibrate Your Miter Saw to a True 90 With a Framing Square
Technique: Miter Saw Square Calibration
The Problem
A miter saw that cuts 90.4 degrees when the scale says 90 poisons everything downstream — every butt joint gaps on one side, every four-piece frame accumulates the error into a corner that won't close, and you end up blaming your technique for what's actually the tool. Saws drift out of square from transport, from drops, and sometimes straight out of the box, and most people never check.
The Technique
The fix is fussy but simple in shape: free the saw's alignment, square it to something you trust, and lock it back down.
- Unplug the saw (or pull the battery).
- Set an accurate framing square against the fence and the blade body — flat against the plate, not touching any teeth, since the set of the teeth will throw off the reading.
- Find and loosen the fasteners that hold the saw's rotation true to its detent stops — the screws or bolts that fix the fence (or the detent plate, depending on the saw) in relation to the blade.
- With everything just loose enough to move, carefully bring the saw to a perfect 90 degrees against the square.
- Retighten the fasteners in that position, then re-check with the square — tightening can shift things, so confirm rather than assume.
Check it once in a while, not just once: a saw that gets loaded in and out of a vehicle earns a recheck every few months.
Pro tip: The truth test for any miter saw is the flip test: crosscut a wide board, flip one half over, and butt the two cut ends together against a straightedge. Any error in the saw shows up doubled in the seam — a gap you can see and measure, with no scale or square to argue with.
Safety note: Do all of this unplugged. You'll have hands on the blade and fence repeatedly, and a miter saw's trigger is exactly where you grab to move the head.