One lesson I've learned in decades of woodworking is that, aside from the finish, it's the joinery that can literally make or break a project. And of all the joints, miters are out in the open for full inspection and must be perfect. So, here are some tips for making miters that other woodworkers will envy. That is the ultimate stamp of approval, isn't it?
Technically, mitering corners means joining stock to hide the appearance of end grain. This can be done on a mitersaw or a tablesaw. But miters can also be cut along an edge (properly called a "bevel"), as when building a box. The mitersaw seems to be an obvious choice in making its namesake cut, and I use it often. But it is limited to making miters across the grain and not long bevel cuts. The tablesaw, on the other hand, is well-suited to cutting both miters and bevels, and this versatility helps cement its place as the go-to tool in most woodworkers' shops.
Set up for success
To begin cutting great miters, it's critical to start with flat, straight stock. Outfit your saw with a sharp blade and ensure that the saw fence and miter gauge are aligned correctly. Even a tiny inaccuracy can cause big problems come assembly time.
Before you begin cutting, you'll need to make a couple of modifications to the miter gauge and one to the tablesaw. The guide bar of the miter gauge should slide smoothly in the tablesaw slot without any side-to-side movement. To eliminate "slop," lay the bar on its side and, using a hammer and a metal punch, peen a couple of dimples on the bar in the area of excess play [Photo A]. Peening the bar effectively makes it wider in those spots. A bit of paste wax in the tabletop slot allows the bar to glide nicely, too.
Second, most any miter gauge will benefit from an extension. I make mine from MDF or multi-ply plywood [Photo B] no more than 3" tall and 24" long. This provides a more stable support for the workpiece, and eliminates tear-out at the end of the cut. The additional length allows clamping a stopblock in place when making multiple pieces of identical length.
My old tablesaw had a plastic disk embedded in the tabletop that could be marked to indicate the precise line of cut. Very useful when cutting any stock, but indispensible for miters. So I modified my current saw to do the same [Photo C].
Next, I set the miter gauge as accurately as I can [Photo D]. Note that for flat stock, as shown in [Photo E], all cuts can be made with this setup, because the workpiece can be flipped over to cut the opposite end. For moldings, you'll need to reset the miter gauge at the opposite angle in the other miter-gauge slot.
Cut tests, then workpieces
With the saw and miter gauge set up, verify the accuracy of your work before cutting into project pieces. Here are the steps I take each time I cut mitered pieces [Photos E–G].
Carefully set up for bevels
Not all cross-grain miters can be cut with the blade set at 90°. The height of a jewelry-box project, for instance, may exceed the maximum height of the saw blade. In this case, lay the stock flat on the table, tilt the blade, and guide the work with the miter gauge. With slight variations, the same steps apply to cutting these miters. I highly recommend using a zero-clearance insert here [Photo H]. In addition to preventing tear-out, small waste pieces won't get stuck in the oversize opening of the factory throat plate.
Before tilting the blade, I use a square to ensure that the miter gauge is 90° to the blade. Then I check the tilted blade with the 45° corner of the drafting triangle [Photo I].
Again, cut one end of all the pieces, then rotate them to cut the opposite end [Photo J]. The tabletop score line doesn't work here, so sneak up on the pencil mark until the cut is perfect. Before removing the finished piece, set a stopblock so that subsequent cuts are identical.
Lastly, some projects call for beveling the stock along its edge. These are generally straightforward cuts with the blade tilted and the stock riding against the rip fence [Photo K].
For a quick review of tablesaw setup, see issue 238 (March 2016) or woodmagazine.com/2sawtuneup.
Written by: Jim Heavy