How does one measure stock for miter cuts?

Question

I have tried unsuccessfully to make picture frames on a few occasions. I find that when I am trying to make a miter joint, I err on the side of caution and start "long" and trim my way down to square. I feel like this is not the best way to execute a miter joint for a picture frame.

What is the proper way to measure for a miter joint? Are you supposed to measure your stock from the outside of the miter (outer edge) or the inside corner of the miter? Are there any helpful tips on this process to make it easier?

Answer 1

I was taught to measure to the inside (mainly because it was important to fit the frame to the glass, which went on the inside) and to cut via a mitre box to the outside of the line marked, that is is to say, less than half mm proud of the full length. Then take a shooting board and trim with a nice tuned hand plane. In practice, you can skip the mitre box if you a have a very fine tooled saw, but I still use the handplane and shooting board.

This article from Popular Woodworking may be helpful: http://www.popularwoodworking.com/wp-content/uploads/2010/11/ShootingBoard2.pdf

Years ago I bought a Jorgensen compound miter saw that I am still quite happy with (although it is no guarantee as to the worth of the current crop). I still use a shooting board with board cut on that saw as well.

Answer 2

Often in woodworking the best practice is to cut slightly over the final size, then sneak up on the final dimension.

One great solution for getting perfect miter joints is to use a miter sled. Once you build the sled, you'll be able to cut square miters every time.

Here are some examples:

• https://www.youtube.com/watch?v=H00prACPflw
• http://www.woodsmithshop.com/download/511/table-saw-miter-sled.pdf

But what about the actual lengths of the pieces? Use stop blocks clamped to the fences of your miter sled to cut multiple pieces to exactly the same length. Presumably you have a rabbet cut into the back so you can insert the glass (if using glass), photo, and backing. Don't measure from the outside corner of a miter joint or the inside corner, but rather from what will become the outer edge of the rabbet. Be sure to make your frame slightly larger than the glass (if using glass) and the photo or mat that you'll be inserting into it.

Common picture frame sizes are 4x6, 5x7, 8x10...notice a pattern? That's right, the short sides are 2" shorter than the long sides. Make a 2"x2" square spacer to help set up for the shorter sides after you cut the long sides.

Answer 3

What is the proper way to measure for a miter joint?

There are often several good ways to tackle a woodworking task, and miter joints are certainly in that category. Whether to measure from the inside, the outside, or along the rabbet depends on your setup and which measurement is most important to you.

If you're using a table saw or miter saw and none of the dimensions are critical, then IMO the easiest way to make a mitered frame is to measure from the outside and then use a stop block. The two things that are essential for getting square corners are:

1. The opposite sides need to be exactly the same length.
2. The ends are cut at exactly 45°.

Using a stop block with either your table saw's miter gauge or your miter saw's fence helps make your cuts repeatable, so that you can be sure that opposite sides are cut to the same length. Another way to do the same thing would be to fasten the opposite sides together and cut them both at the same time, but that might not work well depending on your stock's profile.

Answer 4

I was searching this board for 'picture frames' and came across this question and thought I'd add an answer which might be of interest.

The 'correct' way (i.e. the way every professional frame does it) to trim moulding for picture frames is to use a Morso mitre guillotine (or a copy).

This makes perfectly smooth cuts at any angle (but usually 45 degrees) and has a measurement system that uses a vernier-type scale that allows you to dial in the size of the glass (plus 3-4mm as the glass shouldn't be tight up against the frame), the depth of the rebate in the moulding and then it give cuts accurate to the mm.

You place the moulding against the 45 degree stop (having used one side of the guillotine to make your initial angled cut) read the depth of the rebate from the vertical scale, then set this reading on the top horizontal scale against the desired glass size on the bottom horizontal scale.

So if the rebate depth is 25 mm and the glass size is 350mm, slide the top scale so that 25 is against 350 and then use the foot pedal to tike bites from the moulding. There is a hand control to move the blades in after each cut and 7-8 cuts completes the cut.

https://youtu.be/cG9j8035F3A

I'm in no way suggesting you buy one of these, but thought you might be interested.

You can also get a table-top version with a hand lever, and I believe these are popular with kitchen fitters etc who have to cut a lot of mouldings at 45 degrees.