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To increase the strength of end-grain glue joints, paint the end grain with a thin coat of glue and wait about half an hour. Apply another coat of glue — this time, apply it as thick as you would normally — and clamp the parts together. The first thin coat prevents the end grain from absorbing the second coat, resulting in an even and continuous glue bond. However, don't rely on end-grain glue joints alone when strength is important.

Bond Joining Wood

1-21 The strongest glue joint you can make is long grain to long grain with the grain parallel (1). Long grain to long grain with the grain perpendicular (2) is almost as strong, but the members of the joint move in opposite directions. This weakens the glue bond. A long-grain-to-end-grain joint (3) has some strength, but the end grain absorbs much of the glue and the adhesive film isn't continuous; consequently, the bond is weak. In an end-grain-to-end-grain joint (4), this problem is aggravated. Since both boards absorb the glue, the bond is even weaker.

1-21 The strongest glue joint you can make is long grain to long grain with the grain parallel (1). Long grain to long grain with the grain perpendicular (2) is almost as strong, but the members of the joint move in opposite directions. This weakens the glue bond. A long-grain-to-end-grain joint (3) has some strength, but the end grain absorbs much of the glue and the adhesive film isn't continuous; consequently, the bond is weak. In an end-grain-to-end-grain joint (4), this problem is aggravated. Since both boards absorb the glue, the bond is even weaker.

You might also consider whether you need to increase the gluing surface at all. Providing a suitable gluing surface does not necessarily mean a large gluing surface. You can build strong, durable projects without oversize, intricate joints. (See Figure 1-22.) There are several other important things you can do to ensure a good glue joint:

■ Make the glue surfaces as smooth as possible. A thin, even, continuous film of glue is essential for a strong joint. Rough surfaces make the film uneven and create voids.

■ Fit the surfaces properly. The surfaces must fit together without any gaps. Gaps create an uneven glue film and weaken the bond. At the same time, the fit must not be too tight. A tight fit will squeeze the glue from between the boards, leaving a weak, "starved" joint.

■ Clean the surfaces. Give the glue surfaces a light sanding with very fine sandpaper before applying the glue. This removes any foreign materials. It also helps the glue to soak in and form what chemists call an "interface" — an integral bond between the adhesive and the wood. As you sand, be careful not to round-over adjoining surfaces.

I -22 You don't need beefy, intricate joiner)' to make strong glue joints. This reproduction of a Shaker lap desk is made from thin stock (many parts are only V32 inch thick) so it is as light as possible. With the exception of the dovetail joints at the comers, the joinery consists of simple butts, rabbets, and grooves. But the assembled desk is sound and solid.

I -22 You don't need beefy, intricate joiner)' to make strong glue joints. This reproduction of a Shaker lap desk is made from thin stock (many parts are only V32 inch thick) so it is as light as possible. With the exception of the dovetail joints at the comers, the joinery consists of simple butts, rabbets, and grooves. But the assembled desk is sound and solid.

The considerations are similar if you're making a fastened joint. The first thing that comes to mind when you must provide a suitable anchor for a nail or screw is to beef up the wood around it. But this isn't the only thing you can do to strengthen a fastened joint. As with a glue joint, you must consider the orientation of the wood grain. Nails and screws hold better when you drive them through the long grain. They may pull out or even split the wood if you drive them into the end grain. You can also:

■ Use more, smaller fasteners instead of a few large ones.

■ Drive fasteners at angles to one another, locking the parts together. (See Figure 1-23.)

■ Use square-shanked nails or ring-shanked nails instead of ordinary nails with round, smooth shanks. The large surface area of square-shanks and the protrusions on ring-shanks help to hold the nail in the wood.

■ If you must drive screws or nails into end grain, use fasteners that are as long as practical. The extra length helps them to hold tight.

Nail Join Wood

I -23 Here are two ways you might lock boards together with nails. In the butt joint (top), the nails are driven at slight angles, alternating right and left with each nail. In the miter joint (bottom), the nails are driven at right angles to one another. In both cases, the opposing angles of the nails make the joint difficult to pull apart.

I -23 Here are two ways you might lock boards together with nails. In the butt joint (top), the nails are driven at slight angles, alternating right and left with each nail. In the miter joint (bottom), the nails are driven at right angles to one another. In both cases, the opposing angles of the nails make the joint difficult to pull apart.

The Value of Simplicity

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Responses

  • maire
    Can you join wood together to make it longer?
    8 years ago
  • florian
    How to join wood boards?
    7 years ago
  • angelica oldbuck
    How to connect wood together with nails?
    2 years ago

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