62 - Box Joint Jig, страница 8

#6 x %" Fh WOODSCREW

THICKNESS OF 14" HARDBOARD

TOP VIEW c?

parts — a fence plate and a carrier plate, see Figure 5. The fence plate (D) starts off as nothing more than a piece of V4" plywood, cut to size. A shallow dado is cut in the front of this piece to hold a replaceable backing insert that will be added later.

In order to position this dado, I installed a V4¹¹ dado blade in my table saw. Then the fence plate is placed against the carriage of the jig, making sure the two are flush on the ends. With a pencil, mark the location of the dado blade on the edge of the fence plate (Figure 6).

Then with the jig removed from the table saw, cut a dado that is V4¹¹ wider on each side of the markings (Figure 6a). By using the rip fence as a stop, I was able to cut the same-size dado on all five of the fence plates I was making.

Once the fence plates were finished, I made the carrier plates. The carrier plate (E) is an important part of the jig. It not only supports the workpiece while the box joints are being cut, it also holds an index key that is used to space the box joints. This key will be fitted into a shallow slot in the carrier plate.

As you can see in Figure 7,1 cut the slot for the key on my table saw,,—\ using the jig to back up the carrier plate. The width of the slot (and the key) has to match the width of the

FRONT

INDEX KEY

view")

fa SIDE VIEW

" (CROSS SECTION)

FENCE 1. || PLATE ' I

#& x W Fh WOODSCREW

INDEX KEY

SLOT

k Replaceable Insert. A hardboard backing insert can be easily replaced as it gets chewed up through use.

The second part of this jig is the fence. Or maybe I should say "fences." That's because you'll want to build a separate fence for each size of box joint that you want to make. But this isn't as much work as it may sound like. Except for the size of the index key, the fences are

identical, so you all you have to do is make multiple parts for each one.

If you take a look at the box on the opposite page, you'll see that I made a total of five different fences for the five most common sizes of box joints I use (¹/8",¹/4",³/8",¹/2",and³/4¹¹).

The fence consists of two main

Fence

CARRIER PLATE

INPEX KEY

('/4" WIDE KEY SHOWN)

'A" x 2" CARRIAGE BOLT

ADD 'A" TO EACH SIDE OF DADO

BACKING INSERT

^E)

V*" WASHER

'/4^m

STAR KNOB

CARRIER PLATE

^ SHIFT YOUR CARRIER PLATE DOUBLE THE WIDTH OF YOUR DADO SET

3 ■ CARRIER PLATE (V4" Hdbd.)

WIDTH OF 'A" DADO SET

8

ShopNotes

No. 62