Small Screws.

Progress, Volume I, Issue 3, 2 January 1906, Page 63

Small Screws.

The smallest screws in the world are made in a watch factory. They are cut from steel wire by a machine, but, as the chips fall from the knife, it looks as if the wire was being cut up for fun, for no screw can be seen, though one is made every third operation. The fourth jewel wheel is the next thing to being invisible, and to the naked eye it looks like dust.

With a glass, however, it is seen to be a small screw, with 260 threads to an inch, and with a very fine glass the threads may be seen very clearly. These little screws are four one- thousandths of an inch in diameter, and the heads are double in size. It is estimated that an ordinary liqueur glass would hold 100,000 of these tiny little screws. About 1,000,000 are made every month ; but no attempt is ever made to count them. In determining the number, 100 of them are placed on a very delicate balance, and the number of the whole amount is determined by the weight of this. All of the small parts of the watch are counted in this way, probably 50 out of the 120. After being cut, the screws are hardened and put in frames, about 100 to the frame, heads up. This is done very rapidly, but entirely by sense of touch instead of sight, so that a blind man could do it just as well as the owner of the sharpest eyes. ■ The heads are then polished in an automatic machine, 10,000 at a time. The plate on which they are polished is covered with oil and a grinding compound, and on this the machine moves them very rapidly by a reversing motion, until they are fully and perfectly polished.