Tongueand Groove Joints

The tongue-and-groove joint is the older brother of the splined edge joint. Instead of a separate spline, you have a solid spline that's an integral part of the board.

Like the splined edge joint, the tonguc-and-groove joint is used where surface loading might be considerable—in tabletops and the like. It's also a traditional joint used in breadboard constructions. The most familiar uses these days may be in the carpentry realm—tongue-and-groove siding, paneling, and flooring. Here the joint provides a mechanical lock between boards that are fastened to another surface or a frame, rather than to each other. It also provides a rudimentary aesthetic—the wood can shrink without opening the joint enough to expose whatever is behind it.

You probably think of the tongue-and-groove as a through joint, but if cut with a router, it can easily be stopped so the interlock doesn't show on exposed edges. In addition to stopping the grooving cut, you have to trim back the tongue so the joint will close.

Typically, on Winch stock, you have a '/-»-inch-wide by '/-»-inch-deep

The tongue has to Jit the groove properly to get the most out of the tongue-and-groove joint. If the tongue is too long, it bottoms in the groove and prevents the joint from closing. Too short a tongue, on the other hand, weakens the joint. If the tongue's too thick, it can spread— and possibly break—the groove, giving you an uneven surface. But this perfect fit is; strong and attractive.

The tongue has to Jit the groove properly to get the most out of the tongue-and-groove joint. If the tongue is too long, it bottoms in the groove and prevents the joint from closing. Too short a tongue, on the other hand, weakens the joint. If the tongue's too thick, it can spread— and possibly break—the groove, giving you an uneven surface. But this perfect fit is; strong and attractive.

groove, centered across the edge. The tongue thickness matchcs, but its width is usually M«* inch. The Mo-inch difference is there to accommodate wood movement and glue. Thicker stock calls for a thicker, longer tongue. If the joint will be exposed, or if it isn'ttobcagluedjoint(asina breadboard end application), the disparity between tongue width and groove depth can be narrowed.

The joint should be a firm press fit: If you have to knock the pieces together, then struggle to pull them apart, the joint's too tight. But you don't want it to rattle either.

Cutting the tonguc-and-groove, the way I do it, involves the horizontal router table and a hand-held router, a straight bit, and a rabbeting bit. On the horizontal table, I use the straight to plow the groove. Then I cut the rabbets, forming the tongue, with the other router and bit. Doing it this way allows me to maintain both setups until the job is completely done. I don't know that I need to preserve them, but I'm more comfortable psychologically if 1 do. That should count for something.

All the stock has to be the same thickncss, and you need a couple of scraps lu lest the setups.

On the butt end of a scrap, mark the proportions of the joint. Only mark the groove. With the scrap on the far side of the bit, set the depth of cut and the height of the bit above the table to match the layout. As a practical matter, don't try too hard to get the cut centered on the stock.

Make one pass with the scrap, then flip it over and make a second pass with the other face on the table.

To set the bit to form the tongue, use a groov ed scrap. Hold the scrap on the router table with the grooved edge against the cutting edge of the slot cutter or rabbeting hit. Adjust the hit height to exactly match the distance to the groove.

Router Tables Horizontal

To set the bit to form the tongue, use a groov ed scrap. Hold the scrap on the router table with the grooved edge against the cutting edge of the slot cutter or rabbeting hit. Adjust the hit height to exactly match the distance to the groove.

| BIT DRAWER

If you have a lot of tongues and grooves to cut, a special tongue-and-groovc assembly may be a worthwhile investment.

The typical assembly—Amanas Ls shown here—consists of an arbor with an integral shank, two identical, removable cutters, and a couple of bearings. The bit is intended for use in a table-mounted router, and its configuration guarantees that you'll be able to keep the stock fiat on the tabletop as you rout it. The bit will work on stock between '/; and ¥* inch thick.

When setting up the assembly for cutting rhc tongues, you sandwich one bearing between the two cutters. Line up a piece of the stock next to the cutter, and adjust the cutter height to center the tongue on the stock's edge. Make a few test cuts and monkey with the setting a bit until you are happy with it. Then set up a couple of feathcrboards or other hold-dowas. and rout the rongues.

To set up for cutting slots, you mount one of the cutters between the two bearings. Don't remove the shank from the router; it's easier to do this when it's still held by the collet. Use a piece of the stock with the tongue to set the cutter height. Simply line the cutter up even with the tongue. If the tongue is slightly offset, then the groove will be equally offset. Make a test cut, and fit it on the tongue to confirm that your eye is good. Happy with the setup? Make sure the feathcrboards are still in rhc right places, then rout the. grooves.

Amana s assembly is a compact bit. and it is supplied with a selection of brass shims you use to adjust the fit of the joint. According to the manufacturer, the shims usually aren't needed until after the cutters have been resharpened a time or two.

The advantage of the assembly is the perfectly matched cuts that are possible. Since you are using the same cutters to produce both the tongues and the grooves, they're guaranteed to match. And

Amana's tongue-and-groove bit assembly is a worthwhile investment if you'll be doing a lot of tongue-and-groove work. It's configured here to cut the tongue, which it can do in a single pass. And if the groove should be cut off-center, as in the sample, you can easily make the tongue off-center loo.

because you cut both shoulders of the tongue in one pass, you can make the tongue offset to match an offset groove (and vice versa). The disadvantage, of course, is that you have to dismantle the bit when switching from one cut to the other.

This ccnters the groove. It may be a tad wider than '/■• inch, but as a practical matter, that's irrelevant. Besides, many bits are a trifle undersized.

Now use the scrap to set the height of the rabbeting bit in the other router. Cut the tongue on a second scrap, then test the fit. adjusting the rabbeting bit setting if necessary. When the settings are right on, cut the good stuff.

You can do the job in other ways, of course, depending upon your equipment, your bits, and your work predilections.

On the horizontal table only, set up for the groove as I've already described. Cut all the grooves necessary. Remember to make the two passes for each groove so it is

The same horizonlal table setting serves for l>oth rabbeting cuts neces-sary to form the tongue. Make the cut on the tabletop side of the stock. Feeding the bulk of the stock betw een the tabletop and cutter is risky business, with lots of kickback potential.

centered on the edge. Then change rhc setup to do the tongues. Keep the same bit; use a sample of the grooved stock to reset the bit projection and the bit height so you can cut the rabbets that form the tongue. Cut a sample, and test its fit in the grooved material. Make a pass with one face down to cut the first rabbet, then flip the board over and make a second pass to complete the tongue. Adjust your settings if necessary. Then rout the job.

On the router table, the routine is pretty much the same as for the horizontal table. While you can use a straight bit to cut both the groove and the rabbets that form the tongue, Fred uses a '/»-inch slot cutter.

Set the cutter height for the

To slot the edge of a large panel, rest it on the hack of the router table. Note that the fence is positioned to keep the w orkpiece off the slot cutter's pilot, so the depth of the cut will be reduced. ¡Voir also that the fence is blocked up so that the bit guard will clear the arbor nut.

grooves, getting as close as you can to centering the slot on the stock. Typically, slot cutters make a Winch-deep cut. so you need to set the fence to limit the cut depth to V* inch. To center the grooves, make a pass with one face against the tabletop, then flip the stock over to make a second. Groove all the stock in this two-pass fashion.

For the cuts that form the tongue, use a rabbeting bit. Change bits, and use a piece of the grooved stock to set the height. Always make the culs on the tabletop side of the stock; otherwise you could trap the work between the bit and the tabletop. Adjust the fence as necessary' so that the tongue won't be as long as the groove is deep. Cut a test piece and check the fit. Adjust the bit height or fence if necessary. Then rout the tongues on all the stock.

With a hand-held router only, use the slot cutter-rabbeting bit combination. This way. you can keep the router on the face of the work for both the grooving and tongue-forming cuts.

Setting up for the cuts follows the routine described for setting up the router table. Instead of a fence, use an edge guide to control the slot cutter's depth of cut.

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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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Responses

  • angelica
    Where tongue and groove is exposed?
    2 months ago
  • esa
    When would you use a tongue and groove joint in carpentry?
    4 days ago

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