Miter With A Secret Partner

FIGURE I

WASTE

PLYWOOD FENCE

FIGURE I

We used miter and spline joinery on every project in this issue. That alone should indicate it's quite a versatile joint. Miters can solve a lot of problems — especially on any type of frame that requires special cuts along the edge.

For instance, you can make molding cuts or rabbets — either on the inside or outside edge — before the pieces are mitered. This eliminates many of the headaches associated with other frame joints (like a mortise and tenon).

However, miters do have their bad side. In fact, eross miters (cut across the face of a board) and end miters (a bevel cut at the end of a board) are probably the two worst joints in woodworking.

The problem with both of these joints is that you're joining end-grain to end-grain. And no glue (no matter bow strong it is) will hold this kind of joint together (for long).

However, there is a simple solution: a spline. If a groove is cut in both mitered pieces, a spline can be inserted to strengthen the joint considerably. The spline not only adds mechanical strength, but it also provides a good glue surface (long grain to long grain) between the sides of the groove and the spline.

Yet, this solution creates another problem: How do you cut the grooves for the splines. . . accurately? In fact, how do you cut the miters accurately?

SETTING THE ANGLE

The first step for cutting a miter is to set the angle of the cut. The accuracy of your setting, however, is limited by the accuracy of the markings on your saw. Most miter gauges and radial-arm saws leave much to be desired.

To get an accurate setting I use an adjustable protractor, (See Talking Shop in Woodsmith No. 20.) This type of protractor can easily be adjusted to fractions of a degree, and is well worth having in the shop. Adjustable protractors can be found at almost any art supply store, or in the Garrett Warfe Catalog.

MAKING THE CUT

Even if the angle is accurate, the miter cut itself can still be off. The culprit here is the saw blade. It's the nature of a saw: blade to either pull the workpiece into the blade as the cut is being made, or push it away. This "creeping" throws the cut out of line. To get around this problem, I use the following procedure.

First, I cut all the workpieces to rough length — about 1" longer than needed for the final length. Then I set the miter gauge to the proper angle.

fence am) stop. When working on a table saw, I attach a plywood fence to the miter gauge. The fence supports the work-piece all the way to the blade, and also pushes the waste out of the wray.

To prevent the "creeping" mentioned above, I fasten a stop block to the fence, see Fig. 1. The stop is helpful in three ways. If the saw blade tends to push the workpiece away, the stop prevents it. If the blade tends to pull the workpiece, you can counteract this action by pushing the workpiece toward the stop. Also, the stop is very handy for cutting several pieces to the same length.

making the CUT, I like to sneak up on mitered cuts — making two cuts on each mitered end. Although this two-cut procedure is rather time-consuming, the result is an accurate miter.

As mentioned above, ail of the work-

pieces have been cut to rough length. Then the first cut for the miter is made. This cut clears away most of the waste on only one end of each piece. I use the stop to make this cut so all pieces are cut to the same length.

The second cut is a trimming operation. 1 move the stop about Vi« closer to the blade, and trim off the very end of each piece. Since only one side of the blade is in contact with the wood, it has less tendency to pull or push, and the cut is cleaner and more accurate. Next, 1 mark the final length on the other end of each piece, and repeat the two-cut procedure. This time, both cuts can be lined up by using the kerf in the fence as a guide.

SPLINE GROOVE: CONSIDERATIONS

Now that the miters are cut, a groove must be cut for the splines that join the pieces together. These grooves can be cut on either a table saw or radial arid saw. However, it's difficult to cut a stopped groove — especially in narrow pieces.

There is another way. Ever since we built the router table (shown in Woodsmith No. 20), I've come to rely on it as an easy and accurate way to cut spline grooves — especially if the groove must be stopped.

After experimenting with this type of operation a little, I found three helpful additions to the router table.

secondary top. The router table's top is designed with a 1V4 "-diameter opening for the router bit. I made a secondary top by drilling a V* hole in a piece of scrap Mcutonite. This top is temporarily clamped to the old top to provide a smooth surface on all sides of the bit (which is necessary when working with very small workpieces).

gariuue HITS. Since we usually work with hardwoods, I dug deep in my pocket and bought a W carbide-tipped straight router bit. Although this bit is expensive, it's excellent for cutting spline grooves.

auxiliary fence. When cutting a spline groove in a cross miter, it's very helpful to clamp a higher fence to the adjustable fence on the router table. I just use a 4" strip of W plywood, see Fig. 2,

For an end miter, you'll need a fence that's beveled at the same angle as the miter. Here I simply bevel-rip the edge of a 2x4, see Fig, 4,

WASTE

PLYWOOD FENCE

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