Wood-working for Beginners: A Manual for Amateurs

by Charles G. Wheeler

Fig. 666.

In boring holes for screws, considerable discretion must be used. The hole in the outer piece (the one nearer the head of the screw) should be large enough to allow the screw to slip through freely—that is, you should not screw it into both pieces, but only the inner one, the screw acting somewhat in the nature of a clamp to bind the outer piece to the inner by pinching it tight between the screw-head and the inner piece (Fig. 666). How much of a hole to bore in the piece into which the point of the screw enters depends on circumstances. The stouter the screw the less hole required. The softer and larger the piece and the farther from the edge the less hole required. If the piece is small or liable to split, the hole must be carefully made—the more carefully in proportion to the slenderness of the screw, as a slim screw is liable to twist off in hard wood unless a sufficient hole is provided. Brass screws are very apt to do this, and much care must be used, particularly with slender ones in hard wood. If the hole is a bit too large, they will not hold. If a trifle too small, they will twist off, which is very annoying, especially in such cases as hinge-screws, for instance, where the place for the screws cannot well be changed. The hole should be somewhat smaller than the diameter of the screw. In good-sized pieces of soft wood there is frequently no need of any hole.

In rough work, especially in soft wood, the screws may be pounded part way with the hammer, driving them home with the screw-driver. Some theoretical workman will be quite sure to tell you never to do such a thing as that, so be sure to understand what is meant. Theoretically there may be some loss of holding power by that process, but practically the screws will hold just as well for the cases in which you are advised to do that way. Judgment must be used about all such things and theories are only of value when used by the light of common-sense. For example, if you are screwing the top on a mahogany table or framing a nice boat never think of using a hammer to start your screws, but if you are putting cleats on an old shed door or screwing up a packing-case do not spend an hour and a lot of strength driving screws all the way with a screw-driver when you can do the work in half an hour by driving the screws three quarters of the way in with the hammer. Good practical workmen are just as certain to use the hammer in such cases as they are careful not to use it for nice work or where the full holding power of the screw is needed.

Flat-headed screws almost always should be countersunk (see Countersink), for neatness if for no other reason, and in hard wood you should cut the depression for the head of the screw with the regular countersink made for the purpose. This should be done for nice work in soft wood where a good surface is required, but for common work in soft wood there is no need, as a rule, for the head of the screw will sink itself easily until flush with the surface.

If a screw hole requires to be moved a little, but not far enough so that a new hole can be bored without the bit slipping into the old hole, plug the old hole with a wooden pin dipped in glue, and when dry bore the new hole where required.

See Screw-driver.

Fig. 667.

Scribing.—Compasses are often used for scribing a line parallel to another line or surface, whether regular or irregular, in places where the gauge cannot be used. Suppose, for instance, you wish to cut the edge of a board to fit the undulating surface shown in Fig. 667. Run the compasses along with one point on the surface and the other making a mark on the board, and the line on the board will be parallel with the surface.