A glued tongue and groove joint is not much stronger than a plain glue joint. The real virtue of a tongue and groove comes when the wood is free to move apart. Tongued and grooved boards can shrink in dry weather, but never show a gap. In tongue and groove flooring, the boards gain stiffness from mutual support—a footfall on one plank has to deflect all the adjoining ones as well.
The old name for tongued and grooved stock is match boarding, and the paired (and sometimes combined) planes for cutting the two elements are called match planes. Where a grooving plane cuts a groove, a tonguing plane leaves the tongue. Both planes need a fence pressed well against the face side of the boards. The size of the tongue and groove is usually reckoned at around one-third of the thickness of the wood. Since the irons of match planes can cut only at a fixed width, the fence is usually fixed as well. Thus, a set of match planes for 3/4-inch boards will have irons to cut 1/4-inch tongues and grooves, inset 1/4 inch from the fence.
Since match planes are intended to work with the grain down the length of the boards, they don't need cross-grain nickers. They do need depth stops, and for these to work, the edges of the boards must be well jointed. One board of the pair retains its jointed edge, and just gets a groove down the middle. The tongued board, however, gets a new jointed edge on both sides of the tongue. You either work to a gauged line or rely on the depth stop of the tonguing plane to make these new edges precisely parallel to the old jointed edge that remains at the end of the tongue.
The new edges on either side of the tongue should come out parallel to the original edge, but they may not be the same depth. Sometimes the off-side element of the tonguing iron is left deeper than the near side. This deeper cut leaves an intentional gap on the back side of a tongue and groove joint to ensure that the face side closes first. Fencing the plane against the face side ensures that this gap is where it should be. If you don't want this gap, a few minutes with the tonguing iron on the stone will make it go away.
When planing match boards, start at the far end and work a section until the plane almost bottoms out, step backward, and do the next section until you have done the whole length. Finish with long walks down the board until the planes will cut no more. The final step with any such joint is a sort of countersinking down the top margins of the groove. Tip the corner of a small, fine-set plane into the groove and run it down the length of the plank so it can lightly sink the shoulders. Repeat this with a pull cut down the other shoulder. The object is to add a little clearance in the hidden middle of the joint to ensure that the visible outside closes tight.
The splined joint uses grooves in both boards so they retain their full width, and spans the grooves with a separate tongue, or spline. A splined joint is a good choice for bench tops built up from narrow, thick pieces. You don't lose any of the precious width, as you would with a tongue.
Because the spline can be cross-grain wood, it can be thinner than the one-third of the thickness required for a tongue and groove. The spline can also make a stronger joint if it is tougher stuff than the boards it's joining. The proper spline has its grain running perpendicular to the joint, and it has to be made in short sections. Plane a wide board of hard wood to the thickness required and then saw spline sections off the end. Again, ease the area on the margins of the grooves with a single pass of a fine-set plane.
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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.