Special Joinery Bits

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Woodworkers are constantly seeking the perfect edge joint.

As we've seen in this chapter so far, there are plain edgc-to-edge butt joints, which are only as strong as your glue on a narrow surface can be. The tough part is getting the adjacent boards flush along their entire lengths during glue-up. So woodworkers have come up with joints that provide some mechanical interlock and an expansion of the glue surface—splined edge joints, biscuit joints, tongue-and-groovc joints.

Bit manufacturers have come up with a variety of special bi ts for edge joinery. All the bits require but a single setup. The edge configurations they produce offer some mechanical interlock, expanded glue surfaces, and fast glue-up.

Glue-joint hit. The simplest of these bits produces a sort of tongue-and-rabbet profile. It's a solid bit without a pilot, made only on a Winch shank. It's clearly intended for router table use.

The Amana bit shown on the next page (top) can be used with stock from V* inch to 1 inch thick.

The idea is to mark ihe faces of the stock to be edge-joined. One board in a joint is routed faceup, the other facedown. 11 the height of the bit is just right, the two boards will fall together with their faces flush. Because of the interlock, the boards can't shift up or down.

Some details must be attended to in using the bit. The stock has to Ik flat, and it has to be held firmly to both the tabletop and the fcnce. If the tongue isn't parallel to the edges, either the joint won't close or the surfaces won't be flush along their entire lengths. Stout hold-downs are essential.

There's no pilot, so you must use a fcnce. housing the bit to the maximum degree possible. Use a straightedge to set the fence flush with the deepest part of the cutting edge to mimimize the amount of stock removed. You really want to make the full cut in one pass; the more passes you make, the greater the chance that you'll flub up. with an edge either drifting from the fence or lifting off the tabletop.

To set the bit height, the most imponant adjustment, you have to make test cuts on two pieces and fit them together. If the joint is off by 'A inch, raise or lower the bit only '/«

A glue-joint bit is designed to shape the edges of mating boards so they interlock. One setting sers ices all: One board is routed with its face up. the other with its face down, litis Amana bit is intended for router table use, and since it has no pilot, a fence must be used to guide the work. It will handle slock between % inch and 1 inch thick.

inch. This will move the cut that Va inch on both boards in the joint, amounting to a full '/»-inch change.

Lock-miter bit. The primary purpose of this bit is cutting an interlocking profile on pieces to be joined in an edge miter. The treatment makes it easier to assemble the joint—a plain-edged miter is ornery at glue-up—and increases the glue area.

The trick is that one setup suffices for cuts on borh picces to be joined. When the bit height is just right, you feed one panel flat on the tabletop, the other on edge against a tall fence. Obviously, if the panels are for something on the order of a kitchen cabinet, the fence especially must be very tall and securely braced. Hold-ins are essential, too.

An interesting trick you can do with this bit—and the reason I've included it here in the edge joint chaptcr—is to edge-join flat panels. As with the glue-joint bit. you rout one board with its face down, the other faceup. The two should go together perfectly. All the caveats about working with flat stock and using strong hold-downs apply here.

Amana s lock-miter bit is an impressive chunk of metal. It's close to 3 inches in diameter, so a high-horsepower router with speed control is essential. Run the bit at a reduced speed.

Finger-joint assembly. If you like dado cutters, you'll love this assembly. If you like intricate joints that area breeze to produce, you'l love this assembly.

The finger joint is a positive-negative interlock, in which tapered projections (the fingers) on one piece fit into tapered grooves in the other. The profile expands the glue area threefold. It's the sort of joint used to assemble scraps end to end to

Lock Miter Joint

Thougli you may think of ihe lock miter as a joint for casework, it makes a splendid edge joint for gluing up flat panels as well. The hit— Amana's version of it is shown—forms a shape that provides a mechanical lock at the same time it vastly expands the glue surface in the joint.

ULRE-'S HOW TO U5E. JOINLRV BITS

bottom r i

G1LUE.-JOIMT BIT

LOCK-MITE.R BIT

top first cut first cut first cut

TOP bottom

second cut

top

J T0P

bottom

bottom

assembly assembly assembly assembly bottom top

FIRST CUT

SECOSJD CUT

SECOSJD CUT

top bottom bottom bottom top bottom asslmbly

bottom top first cut

bottom second cut

top

_j top

bottom

ASSEMBLY

FINÇE.R-JOINT BIT

BEARING

ABUTTHKi-EOa / cutter

ABUTTHKi-EOa / cutter

BEARING

finger-slot cutter

•ARBOR ONE FIUCER

finger-slot cutter

•ARBOR ONE FIUCER

insert spacers between cutters.

insert spacers between cutters.

THREE FINGERS

FIVE FINGERS

THREE FINGERS

FIVE FINGERS

This is the bit you use to violate one of the basic rules of woodworking, joining Iwards end to end. You can't glue end grain to end grain, but this bit forms many tapered fingers that present long grain to one another as they interdigitate. The end-to-end joint is surprisingly strong, and as an edge-to-edge joint, it's even better.

make paint-grade trim. You can use it to join boards edge to edge and. with some trepidation, end to end.

The assembly used to cut the joint is not cheap, and when you see it, you can understand why. The Amana assembly shown in the photo at right includes five individual finger cutters, one straight cutter, a ballbearing guide, a '/¿-inch-shank arbor, shims, spacers, and washens. Amanas cutters all feature the European chip-limiting design, which restricts the size of the chip removed per pass. This puts a governor on the feed rate and thus makes for a safer cut. The full assembly is impressive, though it isn't particularly large. At 1 Vi inches in diameter. Amana's bit can be run at full speed in a 1'/2-horsepower router—either hand-held or table-mounted.

To set up the bit, you remove the spindle nut and stack cutters and spacers on the spindle. As with a dado cutter, it's best if you stagger the positions of the cutting teeth from one layer to the next. The bearing is always positioned at the bottom of the stack, next to the shank. The paper-thin brass shims are used between the cutlers and spacers to tighten a joint. You probably won't need to use the shims until after the cutters have been resharpened. Even then, a test cut should demonstrate that they're necessary before you add them to the stack. Setup is easiest to do with the arbor chucked in a router that's cither standing on its head or suspended in a router table.

The particular configuration you use depends upon the thickncss of the stock being routed.

• For stock !Ab inch to Y* inch thick, use one finger cutter.

• For stock Yo inch to nA* inch thick, use two finger cutters.

• For stock 'M6 inch to 1 inch thick, use three finger cutters.

• For stock 1 inch to 1 Mo inches thick, use four finger cutters.

• For stock lMf inches to \ Y* inches thick, use all five finger cutters.

The cutters should be positioned next to the bearing, and the gap between the last cutter and the nut should be occupied by die spaccrs. The straight slot cutter (or abutting-edge cutter, as it is sometimes called) is always used and is always on the top of the stack. This cutter, by the way, is actually a micromicron smaller in diameter than the finger cutters. The grooves that the finger cutters form thus are deeper than the shoulder formed by the straight cutter. This provides space for surplus glue at the tip of each finger.

The cutting sequence is the same as with the previously described specialty bits. You rout one workpiece's edge with the stock faceup and the other picce with the stock facedown. When the bit height is correct, the two pieces should slide together with their faces perfectly flush.

MORTISE-AND-TENON JOINTS

From post-and-beam to furniture, the essential frame joint is the monise-and-tenon. Examples of the joint that date back 5,000 years exist in museums. Even today, it's widely used in everything with a wooden frame. Yet It is a joint that many woodworkers avoid, because it seems too involved and time-consuming to make and fit properly.

One of the most common applications of die morrise-and-tenon joint is in the leg-and-rail construction used in tables and chairs. It's used in all sorts of framc-and-panel construction, particularly frames for doors.

Mortise-and-tenon joints take many different forms. The basic elements arc the mortise, which is a hole—round, square, or rectangular—and die tenon, which is a tongue cut on the end of the joining member to fit the mortise. Once assembled with glue or pegs, the mortise-and-tenon joint resists all four types of stress—tension, compression, shear, and racking. And it does it better than any other type of joint. The joint's strength stems from the way it interlocks. The shoulders on both sides of the tenon prevent twisting.

Principal among the types of mortise-and-tenon joints are:

• Open mortise-and-tenon

• Through monise-and-tenon

• Blind mortisc-and-tcnon

• Haunched mortise-and-tenon

• Stub monise-and-tenon

• Round monise-and-tenon

• Mortise and loose tenon

The router is an excellent tool for making any of these, so long as the mortise isn't too nanow and deep.

The traditional way to make the mortise is to chop it out with a mallet and chisel. The tenon is sawed out with a backsaw. It's slow work, and doing it well demands the kind of skill that comes with repetition. To speed the job, most woodworkers rough out the mortise on the drill press, then clean the walls with the chisel. (A woodworker who docs a lot of mortising may invest in a hollow-chisel mortising attachment for the drill press, which actually bores a square hole.) Most woodworkers cut the tenons on a table saw. But the router can do both jobs just as quickly.

The main advantages of the router for mortising include the smoothness of its finished cuts and the accuracy of placement and siz

VARIATIONS ON TUE CLASSIC. MORTISE.-AND-TENON JOINT

Round Mortise And Tenon Oval
UAUNCNÊP MORTISE-AND-TENON STUB MORTISE-AND-TENON ROUND MORTISE-AND-TENON MORTISE ANO LOOSE TENON
Finger Joint Scrollsaw Jig

mortise tenon

tenon mortise

Adjustable Finger Joint Jig

This cutaway shows the difference in Jinish between a routed mortise (left) and a chiseled one (right). The differences are immaterial cosmetically, since the insides of the mortises are hidden. But a smooth surface yields a superior glue joint.

Horizontal Routing Jig

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Woodworking Tools and Installation Tips

Woodworking Tools and Installation Tips

There are a lot of things that either needs to be repaired, or put together when youre a homeowner. If youre a new homeowner, and have just gotten out of apartment style living, you might want to take this list with you to the hardware store. From remolding jobs to putting together furniture you can use these 5 power tools to get your stuff together. Dont forget too that youll need a few extra tools for other jobs around the house.

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