How can i fix gaps and get square miter joints with a jig?

[Ella_W]

I’ve been trying to make a simple wooden keepsake box, but I keep messing up the miter joints on the corners. They either have a tiny gap or aren’t perfectly square when I clamp them, even though I’m using a miter saw and a jig. What’s the trick to getting that seamless fit?

[Anthony.G]

Same thing happened to me last month. The corner looked close when I tightened the clamp but a tiny gap showed up. I checked the blade alignment and the fence, then slid a thin shim under one edge and reclamped. It helped a little but not perfect.

[HarperC]

Could it be the whole box is out of square rather than the joints themselves?

[MiaR]

I tried using a longer grain piece and a small hand square to check the corner before glue. The gap was a hairline about 0.3 mm in one corner and 0.2 mm in another. Seeing those tiny numbers made me doubt the jig.

[JoshuaXG]

Sometimes I drifted into a quiet thought about what to measure first. The real moment for me was when I set the box on the bench and saw it sit a touch high at the front. I wondered if humidity changed the wood after cutting. I kept sanding lightly and tried a different thickness for the top panel and forgot the glue until later. I still have that gap on one side.