This Week in the Shop: 4 Joints For Picture Frames
I’ve been experimenting with picture frames this year. I’ve made a few in school, developed a brindle-jointed Arts & Crafts influenced design, even filled the frame with mirrors and clay. I figured it was about time to report on my experiments.
First, a little anatomy lesson. The decoration we hang on the wall has quite a few parts when its done professionally. The outer frame or molding, a plastic or glass glassing, paper or cloth matting, etc. In my experiments, I’ve cut down the number or parts to three – the frame, glazing and dust cover. Of these three pieces, the hardest part to manufacture is the outer frame.
The outer frame has a few critical components: the rabbet, the width of the outer molding and the joints. The rabbet should be deep enough to accept all the glazing, mats, artwork, etc. The width of a piece should be somewhat proportional to the size of the artwork itself. Lastly, the joint keeps everything stiff. Miter joints, the classic look cut at 45° angle, look amazing, but often need reinforcement. I haven’t experimented yet with miter joints, so I won’t be discussing them in this article.
I’ve used a number of different methods to create the rabbets in my frames. I started out by freehanding the rabbets using a rabbeting bit on my router table, in a manner similar to the video below. I then cut out the corners with a sharp chisel.
In my current set of frames, I just use a straight bit and fence to create the rabbet, running the outer frame like so much molding. I find I don’t notice the rabbets showing on the outside.
I experimented with four types of joints: pocket screws, half-lap joints, bridle joints and mitered half-lap joints. I’ve listed them from least complicated to most complicated.
Pocket Screw Joints:
I used pocket screws on two projects: the full-length mirror and an art piece. Kreg makes an incredible jig and has a number of great videos on how to use them. Pocket screws make tight, easy to assemble and dissemble joints. Pocket screws, though, do have some mechanical limitations. A miter frame, such as the one made below, would most likely crack open if dropped. End-grain to end-grain is a terrible joint, mechanical fastener or no.
I used half-lap joints during my latest frame production run and a few other pieces. Half lap joints offer several advantages over pocket screws. First, tight joints are stronger since they are glued together rather than fastened together. Second, unlike pocket screws, half-lap joints can be created using hand tools. I like being able to export a home project into the classroom shop. Here’s a diagram of the half-lap joint next to a completed corner.
I completed a number of pieces with brindle joints. Bridle joints look classy and allowed for the introduction of curves into my pieces. Unfortunately, this joint is fussy to set up, requires a table saw and some aftermarket accessories or it requires a few hand tools and lots of patience to complete. I had a number of chances to practice and I was never satisfied with the results.
Mitered Half Lap Joints
As I stated early in article, the standard joint in professional frame-making is a reinforced miter joint. A mitered half-lap joint combines the best of the visual aesthetic (the 45° angle) with the strength of a structural joint (half-lap). Whether using hand tools or power tools, mitered half-lap joints fall into the intermediate category of difficultly to create. They are, however, painstakingly hard to get right. Each of the eight face angles must be exactly 45° or the whole piece won’t fit quite right. And catching exactly 45° can be difficult, even with a table saw, miter saw or shooting board. It takes a lot of fiddling to get those angles exactly right.
Of course, once you get them right, everything else is gravy…
So there you go – 4 joints to include in your next picture framing project. I do intend to make another This Week in the Shop post on a picture frame called the “Schoolhouse” or “Crossover” frame. Keep an ear out.
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