An old apprentice of Sir William Fairbairn writes: " For several years it has cost me five dollars a week to keep the bolts on my trip or cushioned hammer-heads in repair, and, finding it to wear on my patience, I tried all kinds of iron, but to no use; break they would. I finally bored a hole, one third the diameter of the bolts (1 1/4 in.), and put a 3/8 in. hole down, some way below the thread, which formed a tube. I have now run them for three months, and they show no signs of giving out. The wrench used would break the other bolts easily; but it can not do so with these. My work on spindles requires the dies to snap together about nine times in ten, which tells very severely on the bolts."