Sprigs of different lengths and thicknesses are generally used for nailing together slojd-work, but for large or heavy articles cut or beat nails are employed, because their uneven surface is more tenacious, and thus gives greater strength to the joint. Before the nail is hammered in, a hole should be bored with the pin-bit or the bradawl to prevent splitting. The diameter of this hole should not exceed two-thirds of that of the thickest part of the nail, and the nail should be hit straight on the head, to prevent it from bending or going in crooked.
The firm hold of the nail in the wood depends partly on the more or less rough nature of its surface, partly on its length and thickness, partly on the kind of wood, and partly on the direction of the nail in relation to the fibres, i.e., whether it is driven into a long board or into an end piece. The strongest joint is made with beat nails in a cross piece; the weakest with beat sprigs in an end piece. The preliminary boring does not affect the hold of the nail in the wood unless it is too deep or too wide. A hole half the depth and half the diameter of the thickest part of the nail exercises no noticeable influence on the strength of the joint.
The strength of nail-joints
Sometimes it is necessary to sink the nail under the plane of the surface, that it may not present any obstacle to smoothing up or finishing off the work. After the nail has been hammered in by the ordinary method, a small steel punch about 4 inches long and \ inch thick, tapering to a thick point rather less in diameter than the head of the nail, is used to sink it. The punch is placed on the head of the nail, and hammered till the head sinks to the depth required.
Wooden pins are sometimes used for jointing. They are made of straight, split wood, and have four sides, often with bevelled corners, tapering slightly to a blunt point. They are driven into holes previously bored which their bevelled corners enable them to fit closely without splitting the wood. Glue is often added to strengthen their hold. These wooden pins are called dowels.
Sinking the head of a nail.