Читать книгу The Handyman's Book of Tools, Materials, and Processes Employed in Woodworking - Paul N. Hasluck - Страница 165

A very simple experiment, to be made by anyone with a hammer and a few nails, will throw much light on the reason why a nail holds woodwork together. Take a piece of straight-grained deal, about 2 in. wide and 1 in. thick, and mark a line along the centre of one of the narrow sides; drive in various nails in a row, about 1 in. apart, and then split the piece down the middle line so as to expose the nails throughout their length. The smooth wire nails called French nails will be found to have penetrated the wood with very little disturbance of the surrounding fibres, and, as a consequence, they go in easily, and will draw out again with great facility. What hold they have is chiefly by friction from the compressed fibres reacting against the sides of the nails. On the other hand, a 3-in. floor brad, which has a flat square point, produces great disturbance in the fibres. Immediately under the point the fibres are crushed and pushed downwards, carrying others partly down with them so that they press against the sides, and at the same time point downwards. It will be observed that every little group of fibres is like a strut pushing against the nail, and preventing its withdrawal. This experiment may be varied indefinitely; and the effect of boring holes before driving the nails can be studied. The difference also between the holes produced by a gimlet, a sharp bradawl, and a blunt bradawl will be instructive.