We usually only address one issue or question with each post, but this week we were asked two very good questions in the same e-mail. So, we thought that we would take a shot at answering both questions.
1. What’s the difference between Granite Drill Bits and Glass Drill Bit?
Glass drill bits are electroplated, while drill bits for granite and concrete are sintered. With glass bits, the diamonds are electroplated to the surface of a stainless steel blank, using a nickel bonding material. The diamonds are just on the surface.
Granite drill bits are sintered. The diamonds are mixed in a softer metal. As this metal wears away, new diamonds are constantly being exposed.
Glass drill bits will drill granite and concrete, but will wear out very quickly, maybe before the first hole is drilled.
Granite drill bits will drill glass, but they leave a hole with very rough edges. With most applications, additional smoothing and polishing would probably be necessary and the "blowout" on the back side of the glass is more common and more extensive.
2.) Shouldn’t these ”diamond core bits” have a pilot bit?
We've seen a few diamond core bits with pilot bits, but it's simply a marketing issue, because most people think that the bits should have a pilot bit, so one manufacturer puts a pilot bit in. Most manufacturers do not.
The pilot bit would have to be centered in the same way that the core bit has to be centered: Using a notched piece of scrap wood, plastic etc., or used in a drill press or started at a 45 degree angle. If you have to do that with the pilot bit, you might as well just do it with the diamond core bit.
In addition, the pilot bits will also wear out much more quickly and will have to be replaced more often. In our blog post from April 4th, we tackled the question about using pointed (pilot) bits: "Do Pointed Drill Bits Work Better?"
For more answers to your questions, you can always download a free copy of “How to Drill Glass, Tile and Stone." Click here for your FREE copy.
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