Pro tips for making perfect miters
Perfect Miters Every Time
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Miters: 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.
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Miters: 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.
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Miters: Use Scrap Wood Guides for a Perfect Fit
It's darn 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.
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Miters: 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 when extra strength isn't needed. Cutting biscuit slots is a minor job that provides major help at glue-up time.
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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 and online.
Try out a Collins Miter Clamp that we featured in a Stuff We Love video below.
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Miters: 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.
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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.
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Miters: 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.
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Miters: 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.
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Miters: Close Ugly Gaps
You can close a small 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.
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Miters: Make Your Own Corner Clamps
Here's an old favorite trick 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.
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'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.
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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.
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Miters: Guess and Test
There are all kinds of ways to find odd angles and for cutting angles in wood, but most carpenters simply make a guess and then cut a pair of test pieces to see how lucky they are. The angle of these two walls looks to be less than 45 degrees. A good guess would be about 30 degrees. Divide 30 by two to arrive at the miter angle, and cut a couple of scraps at 15 degrees. Here there's a gap in front, so we need to increase the angle slightly and recut the scraps at 16 degrees. When you've zeroed in on the correct angle, the scraps will fit perfectly, and you can then cut the actual moldings.
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Miters: Fit One Miter at a Time
Whether you're edge-banding a tabletop as we're showing here, trimming out a window or door, or learning how to measure baseboards for a miter cut and installing baseboard, it's always best to fit one miter at a time whenever possible. Start with a scrap of molding with a miter cut on it as a test piece. When you have the first miter fitting perfectly, mark the next one. Then cut and fit the adjoining miter before you nail either piece.
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Glue and Sand Miters for a Seamless Fit
Here's a trick to make miters look great, but it only works if you're installing raw trim that will get finished after installation. Apply a thin layer of wood glue to the end grain of each piece before you assemble them. Use a damp (not wet) cloth to remove excess glue from the joint. Sand over the miter with a small piece of 120-grit sandpaper. Sand across the joint and finish up by carefully sanding out any cross-grain sanding marks by moving the paper with the grain from both directions.The sawdust from sanding will mix with the glue to fill any small gaps. Sanding the miter will also even out any slight level differences and make the job look more professional.
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Miters: Tweak the Cut
Even on perfectly square corners, 45-degree angles won't always yield perfect miters. Wall corners can be built up with corner bead and compound, and window and door frames can slightly protrude or be recessed behind surrounding drywall. That's when you have to start fiddling with the angles to get a tight fit. In most cases, you'll be making adjustments as small as a quarter of a degree. If the gap is small (about 1/16 in.), recut one side of the miter. If the gap is larger, you'll have to recut both boards or the trim profiles won't line up.
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Miters: Use a Sharp Saw Blade
You can't cut perfect miters with a dull blade, one with too few teeth or one that's designed for ripping. Check your blade for sharpness by cutting a 45-degree miter on a 1x3 or larger piece of oak or other hardwood. If you don't know how to cut a 45 degree angle, just look at the angle measurements on the base of the miter saw. If the blade cuts smoothly with very little pressure and leaves a clean, almost shiny cut with no burn marks, it's sharp enough to cut good miters. When you check your blade or shop for a new one, look for one labeled as a “trim” or “fine crosscutting” blade. A 10-in. blade should have at least 40 teeth, a 12-in. blade at least 60. If the blade is for a sliding miter saw, be sure the teeth have a hook angle of zero to negative five degrees. Teeth with a neutral or negative hook angle are less aggressive and safer for sliding miter saws. Expect to spend at least $50 for a carbide-tipped blade that'll perform well and last.
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Miters: Use a Shim to Cut a Back Bevel
Cut a back bevel on miter joints that are open in front but touching at the back (acompound miter cut). To create a back-beveled cut on a standard miter saw, place a pencil under the molding. If you have a compound miter cut box, tilt the blade a degree or two to cut the back bevel.
