What Is a Glass Drill Bit?

Cindy Quarters

A glass drill bit is typically used with an electric drill to create holes in glass. It may also be used for tile, ceramics and similar materials. The bit is coated with diamond pieces that act like sandpaper to rub holes in the material being drilled without cracking or breakage.

Glass drill bits are used with an electric drill to create holes in glass.
Glass drill bits are used with an electric drill to create holes in glass.

One of the main differences between a glass drill bit and one designed for wood or metal is that the glass bit is smooth, straight and has a rough texture. Those familiar with the more common twist bit are used to seeing the spiraling flutes of the bit that both cut into the material and guide the drilled-out matter up and out of the hole. The glass drill bit doesn’t have any flutes, because when a hole is drilled in glass the excess material is fine enough that it turns to dust rather than shavings that must be removed from the hole.

Since the bit is coated with diamond chips or diamond dust, much of the bit has the look and feel of sandpaper. During the process of drilling the diamond coating rubs away the glass, creating a hole in the material being drilled. Like sandpaper, the coating comes in different textures, from rough to very fine, so that the coating can be matched to the job.

These have some key differences that distinguish it from other types of drill bits. In the glass drill bit, the diamond coating wears off of the outside of the bit over time, eventually rendering it useless. The bit's longevity depends on how hard the surface being drilled is, how thick, and, in some cases, the skill of the operator. The coating may last for many, many uses or it may only last long enough to drill a single hole. It is important to monitor the bit to make sure it is not worn out, since overusing one can lead to cracking and breakage.

A glass drill bit must be kept well lubricated for the best possible results. This is most commonly done by running water over the drilling surface. Caution must be used as this practice can be hazardous with electric drills. It is important to avoid getting water on the drill itself while it is connected to a power source. Failure to do so could result in harm to the operator.

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