45deg angle

[John Keane]

I have made several trianglular shadow boxes for display of internment flags. The angles are pretty close., but not perfect. Using a Dixey digital gauge the saw blade (right tilt) is 45 degs.
Measuring with the 45 angle on a square each cut is 45degs. When I butt the side pieces at the apex (top) I do not get a perfect fit (90 degs). To get a tight fit (no gap) the interior angle is greater than 45 degrees. I'm stymied. I am hoping that one of you more experienced than I can provide me with a resolution to my problem 45's should be a slam dunk. For me it isn't.

[John TenEyck]

Cut two test pieces at 45 degrees and lay them on a flat surface with one bevel up and the other down. They should mesh together perfectly. Then put them together into a 90 degree joint. It should be tight at exactly 90 deg. If so, then your cuts really are 45 degree, and your problem at the apex must be due to the inner diagonal not being exactly 90 on the end or not being the correct length.

[frank shic]

don't feel bad... PERFECT miter joints are still a challenge for me!

[Allen Breinig]

Is your blade truly at 90 degrees to the table top when you zero the Dixey gauge?

[Anthony Whitesell]

The wixey is accurate +/- 0.1 degrees and only reads to the same. Which is a whole lot of margin for error. You really need +/-0.01 degrees. John has the (a) right approach. Which is also useful for setting up the miter lock bit on the router table.

[Bill Huber]

When I am cutting and have to set the blade at a 45° I set it with my drafting triangle and then make test cut on a 2" x 3/4" wide board on its edge. This give me a lot to measure and it that make it easier to check with my combo square.

[Matt Day]

I don't trust the digital angle gauges, rather I use a plastic architect's triangle on the blade then double check the way John describes.

[John Keane]

John, I have done what you suggested i.e. make the bevel cut then turn the pieces upside down to check the fit. The fit is fine. When I go to glue it up the delta between the inner and outer angles shows up. That is where I am lost. I cut a test board to see the result. Perfect fit but proably 92+ degrees vice 90. ?? R/JFK

[Myk Rian]

If the angles are right on, then the problem is in the lengths.