Create Perfect Miters
Tips for tight miters
When they’re done well, mitered joints look good. They hide end grain and match face grains nicely. But they’re also a pain in the neck, requiring precise cuts and fussy fastening. In pursuit of the perfect miter joint? These tips for tighter miters cover common situations you’ll undoubtedly encounter on the job or in your workshop.
Use scrap wood guides for a perfect fit
It’s dang near impossible to get the length and position of a mitered part right unless you can butt it up against the adjoining miters. To provide a guide, tape or clamp mitered scraps in place. Remove the scraps as soon as you glue the part in place—otherwise, stray glue might make those temporary guides permanent.
Align with biscuits
It’s not easy to align and clamp miters, especially when they’re lubricated with a coat of slippery glue. That’s why woodworkers often use biscuits on miter joints even where extra strength isn’t needed. Cutting biscuit slots is a minor job that provides major help at glue-up time.
Match wood grain
Whether you’re banding a tabletop or making a picture frame, make sure the wood color and the grain pattern match at the miters. Selecting matching wood at the lumberyard takes only a few extra seconds and gives you much better-looking miters.
Square up with corner clamps
With some miter-clamping methods, you need to grab a square and make sure the corner is exactly 90 degrees. Not so with corner clamps; they automatically hold parts perfectly square. They’re available at home centers or online for $10 to $50 apiece.
Miter, assemble then rout
Shaped moldings can be tough to miter, align and clamp. So make life easier by starting with plain square stock. Then, after assembly, grab your router and shape the edges. The risk with this method is that you’ll gouge or splinter parts that are already in place. The best way to avoid disaster is to make a series of shallow passes instead of one full-depth cut.
Slow down your glue
It’s hard enough to align and clamp miters without rushing to get it done before the glue begins to set (in five to 10 minutes, and even faster in warm, dry conditions). That’s why there are slow-setting wood glues, which give you an extra 10 minutes or so.
If you can’t find a slow version at your favorite home center, make your own. If you add one part water to 20 parts wood glue, you’ll gain about five minutes of working time. The water will also weaken the bond very slightly. So if strength is critical, order slow-setting glue online. Titebond Extend is one common brand.
Clamp with your hands
When you’re dealing with small or other hard-to-clamp parts, your hands make the best clamps. Simply rub the glued surfaces together and hold them tightly on a flat surface for about a minute. Let go and allow the joint to set for 30 minutes before handling it.
Micro-adjust with paper shims
If you’ve ever tried to adjust the angle of your miter saw by one-tenth of a degree, you already know how hard micro-adjustments are. Here’s an easier way: Slap a few sticky notes on the fence, make test cuts and add or remove sheets until you get exactly the angle you want.
Feel the difference
When you’re building a box or frame, the opposite sides have to be exactly the same length. To make sure they are, do the touch test: Set the parts side by side and run your finger over the mitered ends. You may not be able to see a slight length difference, but you’ll feel it.
Close ugly gaps
Listen- obviously, we recommend spending the time to get a miter right. But if you absolutely HAVE TO, you can close a miter gap by rubbing it with a screwdriver shank or any hard, smooth tool. We used the end of a utility knife. That crushes the wood fibers inward to make the gap disappear. Even professional woodworkers sometimes resort to this crude trick.
Make your own corner clamps
This is an old favorite among woodworkers: Clamp on notched blocks, then add a bar clamp or two to squeeze the joint. This allows you to put a lot of pressure on the joint without buying any special clamps. If you’re assembling a four-sided project such as a picture frame, join two corners first. Then, after the glue has set, join the two halves of the frame.
‘Lengthen’ a board
Ever cut that last part just a bit too short? There’s a solution for that: First, trim off the inside edge of the too-short part. By cutting off the short edge, you effectively make the mitered part longer. Then trim the same amount off the outer edges of the other three sides. Your edging will be a little thinner than you had planned, but nobody will notice.
Bond joints instantly
Trim carpenters have used this system for years: Apply a few dabs of cyanoacrylate adhesive (aka “superglue”) to one surface and apply activator (or “accelerator”) to the other. Immediately press the parts together and they’ll bond in seconds. No waiting, no complicated clamping setup. Activator is sometimes sold separately ($5 and up), sometimes with the glue. Look for it at home centers or shop online; rockler.com carries a good selection of glues and activators.