Gas-heated Bits.
—These are largely used in factories, and are cleanly, expeditious, safe, and convenient. The type shown by [Fig. 9] is very handy, and the illustration and description are due to F. X. Sommers, Jun., in the American Machinist. A mixture of air and gas enters the pipe at about 10 lb. pressure, or enough to give a hot, blue flame. The part A is of cast-iron, which, on experiment, has been found to last longer without corroding than steel, although copper would be better. The soldering bolt B was made of steel because it kept the correct shape point much longer than cast-iron or copper, although the latter metal is better for transmitting the heat. The point should be tinned before using. This form of soldering head is being used on automatic can-soldering machines, and does the work effectively. It also saves gas. It will heat to the correct temperature in about 11⁄2 minutes.
Fig. 10.—Gas-heated Bit complete
Fig. 11.—Air Inlets in End of Air Chamber
Fig. 12.—Section through Air Chamber and Gas-reducing Valve
Fig. 13.—Details of Cones or Needles
A gas-heated bit invented by W. G. Ryan is shown in [Figs. 10] to [13]. The actual bit A is held in a steel sheath B having a space underneath the bit to allow the gas to pass. The sheath has a row of holes on each side to allow the gas to come through, the flame enveloping the bit when in use. The gas, supplied through a flexible tube, passes through the tube that forms the handle, at the end of which is a small chamber C to admit air, which mixes with the gas to cause it to burn atmospherically, the supply of gas passing through a small cone valve D and thence through the air chamber. In the air-inlet holes E at the end of the air chamber are fitted small cones F to regulate the quantity of air. All the cones, including the gas-valve cone, are connected rigidly together, so that when cutting down the gas supply temporarily, the air supply is automatically reduced, and the gas flame remains in being, although its size is much reduced. It has been found that, in some gas-heated bits, the cutting down of the gas seriously interferes with the proportion of the gas and air mixture, resulting in a back-fire. The device here described has been invented especially to obviate that trouble. To reduce the gas supply and, with it, the air supply also, all that is necessary is a slight forward movement of the fitting to which the cones or needles are attached. The copper bit is kept in position by the sheath or clip, the small bolt in which can be taken out in a moment when special attention to the bit becomes necessary. The connection to the flexible gas tubing is at G, while H indicates a guide and stuffing box for the gas-valve cone or needle.
Fig. 14.—Gas-stove for Heating Bits