Posted by Catharine C. Kennedy- Chatham Center, NY on February 21, 2004
PatrickBought a 3/16" drill bit for glass last night & tried it out this morning. Got two holes with five tries...
Put the drill press speed at it's slowest. Do I need to use oil as cutting fluid? What am I doing wrong?
Thanks!
Catherine,
There are several ways to put holes in glass, some are better than others, it just depends on which one you feel suits the job at hand. Most often I drill the holes last
because I hate to acid etch and silver glass with holes already in it because it can leave steaks around the holes. When I am doing 1/4" bevel glass Christmas ornaments, 100 pcs. or more I sandblast the holes with a 1/16" dia. carbide nozzle in conjunction with a reusable piece of lexan with a 3/16" hole in it. I center the lexan over the area for the hole and come in point blank with the nozzle, the abrasive stream cuts the hole, much like a waterjet cutter. Its much faster than drilling.
The traditional way to drill holes was to use a drill glass bit fashioned from a 3 sided metal file, and ground to a point. This was used with water as a lubricant. While turning the bit the glass the workman would also move the axis of the drill in a conicale movement making the hole form in a cone shape as it pierced the glass. This movement makes the hole bigger than the bit so that the bit can't lock up or jam in the hole, cracking or breaking the glass. On old mirrors and push plates you will notice the holes are larger on the front than on the back for the reason that they were drilled as I discribed.
Core drills or tube drills are another method for drilling holes, so called because the drilling is done with a hollow metal tube.
One tube drill method uses brass tubes or cups with slots machined into them. This method uses a mixture of silicon carbide grit and water as a cutting agent. The slots in the tube serve to hold and disperse the agent as it imbeds into the brass and grinds into the glass effectively cutting it. The abrasive most be replenished as it breaks down.
Another method uses a tube that has industrial diamonds attatched to it be a nickle plating process. This is a more expensive but somewhat faster drilling tool. However the diamonds are only slightly held and may be shed through hard use or heat, This type of drill can ruined on one hole if not handled properly.
The best drill and of course the most expensive is the diamond sintered drill. It is made by mixing the diamond in a bronze powder. This compound it heat fused onto the end of the tube drill with induction heating. Because the diamond is bonded within the bronze and not just plated, it is much more durable and produces a smoother cleaner hole. Also this type of tube drill can be dressed (resharpened to reveal fresh diamonds.) This type of tube drill generally is used with a waterfed head which generously applies water from within the tube drill flushing out the ground glass thus increasing drill life and eliminating chance of heat build up. The main reason for failure when drilling holes in glass.
I also invested in a diamond chamfer tool.It is used after the holes are drill to slightly bevel the holes. This strenghtens the holes edge and eliminates the possibility of chipping when using screws in the holes.
If you have ever pulled a glass sign on or off screws only to have a giant clam pop off the hole, a chamfer tool is the answer.
Pat
Danny Baronian
Catharine,
use either turpentine or kerosene and some modeling clay.
Mask the back of the glass w/ contact paper or transfer tape.
Take the clay and make a cord about 1/4" in diameter, (roll the clay in your hands) about 3" long. Mark the location for the hole and drill on that spot with very light pressure enough to cause a slight dimple. The purpose of this is to mark the spot and prevent the drill from walking. This can be eliminated if a circle is cut in the mask at the hole locations and deeply sandblasted when frosting the glass.
Apply the clay around the hole location and press firmly onto the glass, making a dam around the hole - like a washer or 'o' ring. Put a clean piece of pvc or plywood on the drill table , the glass on that surface. Fill the clay dam with the turps or kerosene and drill slowly, making sure not to apply too much pressure. Try this on a test piece, you'll get the feel of it. Keep the clay dam wet with liquid, and when you get close to going through the glass either ease up on the pressure or flip the glass over and drill from the other side. If you don't do this it will blow out, causing a chip around the hole on the back.
Water can be used but turps or kerosene act as a lubricant and cutting agent.
Danny
Mike Jackson
Tony SegaleCatharine,
I think another suggestion (needing to be made) is to drill your holes in the raw glass before you spend a bunch of hours decorating it. If you break the piece at that point, you are only out the glass and not the pain or redoing it.
Mike
Catharine C. KennedyA loud echo to Mike's suggestion, I know from very recent experience of drilling a finished piece, which is now a finished pieces.
[/img]Yup- already figured that bit out- my original piece of glass is now substantially smaller (but only as far asphaltum!) Thanks for the insights on the "hole" thing!
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