Glass Drill Bits
These special bonded drill bits are what you need for drilling bulkhead holes through glass tanks. The diamond bit will cut a 1 1/8" hole through 1/4" thick glass in approximately 1 1/2 minutes and should be able to cut 30 to 45 holes before wearing out. The steel tube drill will take about 12 minutes per 1 1/4" hole, but lasts much longer.
Steel drills must be used with a carbide compound (1 lb per 50+ holes). A 50/50 cooling solution of antifreeze/water with either a clay or plastic dam ring is required for both types of drills. Instructions included.
These drill bits are generally slow-speed bits. During use, the diamonds eventually wear off of the bit due to the hardness and abrasiveness of the material being drilled. Bonded diamond drill bits must not be used on metal, concrete or masonry and require proper speed and adequate water lubrication.