Accurate and Safe Miters on the Table Saw

By Bill LaHay

The table saw is probably the most versatile machine in any woodworking shop, but that’s not to say it does everything really well. Crosscutting lumber, especially long boards, can sometimes be a difficult balancing act. Things get even tougher when making angled or miter cuts because the workpiece will tend to shift under the pressure of the cut.

The standard miter gauge on most table saws is part of the problem; it has a smooth metal face that isn’t long enough to support the workpiece adequately through angled cuts. Fortunately, you can improve the situation with just a few shop-built accessories.

First, mill a straight piece of hardwood such as maple or oak, at least 2 or 3 inches wide, and attach it to the face of your miter gauge. (The gauge face will have holes already provided for screws.) Let this wood auxiliary fence extend past the blade, then set the miter gauge for the angle required and make a cut to trim the wood fence to length. This will give you a precise end with which you can align your workpieces.

For even better results, you can modify the auxiliary fence by gluing a strip of sandpaper to the face, and/or by adding a stop-block feature that will prevent boards from shifting while they are being cut. The photo above shows an example of this.

An even more versatile accessory is a miter sled, a wood platform with runners that slide in the miter slots of the table saw. Make the base from quality plywood or medium-density fiberboard so it will stay flat, and use hardwood strips for the runners on the underside. The runners should fit in the table slots with no side play. Attach front and rear wood rails (on edge) to the upper side of the base, making sure they are heavy and tall enough to stay intact when you cut through the plywood. (Be sure to keep any screws, nails, or other metal hardware out of the path of the saw blade.)

At this point, you’ve got a crosscut sled for cutting board ends square. Turn the saw on and raise the blade just high enough to cut through the plywood base and a workpiece, then move the sled into the blade to make the first cut. For miter cuts, screw removable wood cleats to the sled base at 45 degrees (or whatever angle you need). Using cleats on both the right and left side of the blade will make the jig more versatile. Keep in mind, however, that perfectly square corners are virtually nonexistent in a house, so if you are cutting trim moldings, adjust the angles to get the fit tight, whether or not your cuts are a true 45 degrees.

Aside from these useful jigs, there are a few other tips for getting good miter cuts:

• Cut twice, first to make a through-cut within about 1/16” of the finished length, then a light trim cut for the final pass.


• Install the right blade: a crosscut blade with 60 or more carbide teeth and a full-width (typically 1/8”) kerf. Thin-kerf blades tend to flex more under side loads such as miter cuts and so can leave an irregular surface.


• If your saw still won’t produce clean miter cuts, use a manual (guillotine-style) miter trimmer or a stationary disc sander to clean up the ends. Be sure to allow extra length on the workpiece for this trimming.
  
  

Shop Tip. You can modify a miter sled to make it even more accurate. Instead of individual wood cleats for angles on the right and left side, mount a right (isosceles) plywood triangle on the sled. Align the long edge of the triangle against the rear rail, and have the 90-degree point aiming forward, centered on the saw blade. Then cut mating workpieces by positioning one on the left side and one on the right side. The advantage here is that even if the jig is off slightly, cutting from both sides will compensate for the error. The two miter cuts might be 44 and 46 degrees respectively, but they will still form a perfect 90-degree corner when assembled.