Page:The Cycle Industry (1921).djvu/50

36 turns screws which lock the parts while he drills holes at each joint for conical metal pegs which keep the tubes in place while the joints are brazed. The frame builder is responsible for the correct alignment of the frame. When the joints are pegged he passes on the frame, or it is taken for him, to the brazing shop.

Brazing. Brazing is done in different ways in different factories, some adhere to hearth brazing, others use the more modern liquid brazing. Brazing is really soldering with hard brass, as distinct from soft solder. In hearth brazing an open fire of "breeze" (small coke) is kept at a high temperature by allowing a pressure coal gas flame to impinge on the glowing coke. The joint of the frame is pushed into the fire, but before the frame builder parted with it he had coated the two metals to be united with a flux to facilitate the flow of the brass.

The brazer has in his hand a "stick" of brass or a spoon filled with brass dust called "spelter." When the joint has reached the correct temperature he feeds it with the "stick" or "spelter," and the flux carries the molten brass into the joint. Parts on which the brass should not adhere are specially coated to prevent the molten brass from sticking to the steel or iron.

The other process, called liquid brazing, consists of placing the joint of the frame or other part into molten brass spelter, heated in a special kind of gas oven. The part is withdrawn when the brass has run into and between the two surfaces to be brazed.

After brazing, the frames and forks go into vats and are pickled. This is a bath of corrosive liquid that attacks the rough spelter and softens it previous to the filing up of the joint, or, if the firm has a sand blasting shop, the rough spelter is blown off by a strong current of air, in which sand or shot is carried, and forced on to the joint from a flexible pipe held in the