Fastening corners of picture frames can be challenging. There are a number ways to accomplish this task and some are better than others. When you are manufacturing picture frames it becomes more and more important that the corners of the frame be held fast as the frames get bigger and bigger. It becomes even more important when glass is used in the picture frame.
There are many options for fastening corners. The first and easiest (note I did not say 'best”) is to use some kind of a mechanical fastener like nails, staples, steel straps, headless pins or screws. Each one of these mechanical connectors has it own problems. Small finishing nails that are driven in with a hammer tend to loosen joints. Screws need to be pre-drilled and look ugly, staples also have to be hammered and using an air nailer and 18 or 23 gauge pins may not be sufficient for larger frames.
The best way to fasten the sides of a picture frame is to glue “splines” into the corners. Yes, it is more more, but the splines look more professional and are unquestionably the best option. They hold the corners firm, they are permanent and they add a nice detail to the frames. To see how to make splines in the corners of your frames … read on.
In order to make splines, you will need to make a jig in order to hold your picture frames while they are pushed through a table saw in order to cut the slots for the splines. For smaller and moderate sized frames a 12' x 9” by 3/4” scrap piece of plywood will work nicely (we'll call this the backer board). You will also need a couple of 3/4” x 12” x 2” pieces of scrap wood for the arms to support the frame.
Start off by cutting the ends of the arms at 45 degrees while the 2” width is vertical through the table saw. Next, mark the backer board so that both or the arms can be attached at 45 degrees from the base, which will allow a 90 degree angle in the middle that a frame corner will sit it. The arms of this jig will want to sit flatly on the area you just made the 45 degree cuts on. When the arms are aligned, fasten them to the backer board, making sure the the screws holding the arms on will NOT contact the table saw blade when the jig is slid through the table saw.
When the arms are afixd the jig is ready to use. All that needs to be done is to align the jig with the fence so that when it is tight against the fence, and the fence is adjusted, the table saw blade will make slice through the corner of the frame. Be sure that the cut through the frame will not interfere with the glass or the picture. The slice should be through the thickest part of the frame.
You will also have to adjust the height of the table saw blade. Remember, you do not need to make huge slots through the corners in order to get a spline that will hold the corners firmly. You will need to make these judgments yourself based on the size and type of frame you are working with and whether or not glass will be used in the frame. After the splines have been glued in and the glue has dried, the extra wood can be cut off and sanded smooth and the entire frame is now ready for finishing.
Copyright Colin Knecht