The making of boles in glass is an operation generally accomplished with diamond drills, but these tools are expensive, so that the amateur naturally looks for a less costly method. The writer has fouud the following a most efficient way, as well as an inexpensive one. Any size holes may be quickly drilled through sheet glass of any thickness, or even plate glass, with precision.
A piece of ordinary brass tubing is fixed to a lead weight, as shown in section in Fig. 1. A is the weight, B a groove capable of taking a driving belt, and C the brass tubing forming at D, the cutter. If holes 1/4 in. in diameter are required, a tube of such dimensions is used, and the head A should weigh about 3 pounds.
The tubing may be placed vertically in a suitable mould and the molten lead poured into the mould. The whole is then placed in a lathe and turned up true, the groove B being made at the same time. Figs. 2 and 3 show the other apparatus necessary, namely, a supportiug framework for the drill, and a driving wheel E, consisting of a cycle wheel. The drill support F and G is fixed to a baseboard II, which may be fixed to any ordinary table J by means of the clamps K, Metal plates L, fixed to the wooden framework, act as bearings for the tubular drill C. M represents a sheet of glass to be drilled, N a rubber cushion consisting of an ordinary umbrella ring, and O a movable block placed just under the point of the drill. A wooden support P, is provided on which to mount the cycle wheel, which is held in a horizontal position and turns on its own hub. A handle Q, pivoted to blocks clamped to the spokes of the wheel, is used to operate the appliance. A crossed belt from the cycle wheel to the lead weight of the drill drives the latter. The teeth of the drill are formed with a triangular file.
It now remains to state the materials necessary for grinding and the mode of operating. The brass tubing alone would not make its way through the glass, however fast it might be revolved. Turpentine together with powdered corundum are the materials needed, the turps being poured down the tube from the top opening, and the corundum fed down the same channel while the drill is revolving. A loose wire rod may be used to ram down the corundum, but care must be taken not to cause a stoppage by a superabundance of this grinding material, otherwise it will give trouble, being most difficult to obtain a passage once the tube becomes choked.
The wire rod also serves to direct the flow of the turpentine to the bottom of the tube, where it is most required. If the corundum and turps have been properly inserted, a grinding sound will soon be heard after turning the appliance. The drill should be lifted slightly at intervals, so as to allow the corundum to get under the teeth of the drill. Properly operated, a 1/4-in. drill can be made to cut a clean hole in a 1/4-in. thick plate glass in less than two minutes. This is working the machine by hand.