The first thing required for perfect miters joints, is cutting “complimentary” miters.  For a picture frame you want to miters that add up to 90 degrees. If one miter is 46 degrees and the other is 44 degrees your good to go. Two 45′s is ideal, but in this case, close is good enough. The best way to get complimentary miters, is with a miter sled. For my sled I used 1/2″ MDF for the base, quarter sawn white oak for the runners, and some scrap Poplar for the fences. To align the fences to the saw kerf, I used my Woodpeckers Precision 12″ triangle.

After you’ve cut all the miters, you have to glue them together. For me, the glue up is where things get a little stressful. Thankfully the glue up can be less stressful with the proper jig. I Used some Woodpeckers precision clamping squares and MDF to make alignment jigs. The jigs provide a 90 degree reference angle, and a good surface to apply clamping pressure to.

Technically your finished after the miters are glued up. However a mitered joint is an end-grain to en-grain bond, as as you may know end-grain joints aren’t as strong as long-grain joints.To ensure the joint doesn’t fail for years to come, it’s best to reinforce it with a key (also called a feather). A key is just a chunk of wood that’s inserted in to a slot cut across the outside of the miter. The best way to make the slot, is with a simple jig on a table saw mounted with a flat ground blade.

Image courtesy of Rockler.com

Image courtesy of Rockler.com

The jigs available locally fall into 2 categories: template & arm style. The template style jigs are usually for circles 4″ in diameter or smaller, and the arm style are for circles 7″ to 8″ and larger. I need to make circles that are roughly 6″ in diameter. Thus, instead of ordering a jig and waiting a week for it to be delivered, I made one last night.

I made it from some scrap 1/4″ thick Lexan, I had leftover from my router table build.  The only unpleasant task involved in its construction, was having to turn off the drill press after every hole, and clean the melted material out of the bits flutes. As it is now, I can make holes from 4 to 14 inches in diameter in quarter inch intervals.

1. Keep the design simple & use cheap/ scrap  materials. It’s a jig and therefore expendable. I’m not saying trash it after a month, but don’t expect it to last 10 years either. If you need to think twice about screwing down a stop block you spent too much on materials.
2. Make sure The sled is well supported. When you’re making a cut, you need to be focusing on keeping the piece back against the fence, and maintaining a smooth motion, not juggling the outboard end of the sled.
3. Use quarter sawn wood for the runner, as it will expand and contract less (I used White Oak).
4. Put a shallow dado in the base for the runner; this makes assembly a lot easier.
5. The fence needs to be perfectly strait. By perfectly strait, I mean within a few thousands.
6. Build the fence so it’s adjustable, i.e use bolts in over sized holes.  This feature really helps when it comes to keeping the fence strait. If the fence develops a bow, loosen the bolts and use clamps or some other method to push or pull the bow out.

Like I said earlier, squaring the fence can be a real pain. While the five cut method takes the guess work out of the process, no tricks exist to make the process go faster. I think it took me about 90 minutes  to get my sled to within 0.002″ per foot. Your probably thinking 90 minutes isn’t that bad. Remember, wood moves with the changes in weather. After a month or two of hanging on the shop wall your sled is going to need to be re-squared.