What’s a pilot bit?

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A pilot drill is a small drill bit used to create a guide hole for a larger drill bit, resulting in a smoother and easier-to-drill hole. It is especially useful when drilling larger diameter holes in wood or metal. The pilot bit is also used in hole saw assemblies and routers to keep the saw tip on the work piece and prevent deviation.

A pilot drill is a small drill bit that is used to drill a guide hole for a larger drill bit. By drilling a hole with a pilot bit, the actual drill bit is able to easily drill a hole of the correct size. Often when drilling larger diameter holes in a piece of wood or metal, starting the hole with a large drill creates a difficult-to-drill scenario that often takes longer to drill than when using a pilot drill. When starting the hole with a pilot drill, the larger drill should only cut the outside edge of the hole instead of drilling the entire surface of the hole.

Even large drill bits tend to create a rough hole when used to drill a hole without assistance. When drilling a hole of the same size using a pilot drill, the edge of the finished hole is usually much smoother. Using a smaller bit to drill the initial guide hole allows the use of a hand drill to drill the hole to size. Without a guide hole, the large bit will usually grab the edge of the material and violently twist the hand drill operator’s wrist. Drilling a large hole in one pass using a hand drill motor is usually avoided, as drilling such holes is typically more successful using a drill press.

Drill bits intended for use with hole saw assemblies and some routers often do not emulate a typical drill bit. In this type of application, the pilot drill is often a modified version of a drill bit. Consisting of a short bit with very elongated twists, the pilot bit is not intended for use as a finishing bit. Created only by punching the initial guide hole in the work piece, the finished hole produced by this type of drill is typically not smooth or perfectly round.

In the case of the hole saw, the pilot bit is intended to keep the square saw tip on the work piece. By having a center drill bit that plunges through the work piece, the large round saw bit isn’t as likely to deviate from its mark when cutting a hole. The twists on the drill bit shank are also used to smoothly pull the cutter through the work. As the drill bit works its way deeper and deeper into the job, the saw is coaxed into the job at a speed that won’t force the saw and cause it to bind.

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