Bit by Bit: A Guide to Selecting the Right Drill

Drilling a hole is one of the basic operations in construction, manufacturing, and other common occupations. It may seem as simple as putting a hole into a piece of metal, however, several factors influence the quality and effectiveness of the resulting hole, including:

Turning speed (RPM)

Pressure applied

Equipment used (Handheld or Press)

These factors in combination help determine whether the hole will adequately perform to purpose for which it was designed

But the most important consideration when drilling a hole is the selection of the bit. A wide variety of specialty drill bits are available, depending on the type of hole needed, the material to be drilled, and the desired appearance of the finished piece.

Standard Bits

Twist drills come with standard flute shapes, margins, and points that, with a few caveats, can be used in most general-purpose applications and on most common materials. They are cost effective and readily available in virtually every fractional, letter, number and metric size a shop could need when ultra-precise holes and optimum performance is not required. Though these bits are optimized for metal, some precautions should be taken when using them on the hardest material. Gentle pressure, low speeds, and liberal use of lubricants will reduce overheating, dulling, and skating.

Specialized Bits

When a job demands more precision or functionality, twist drill styles specific to the material being drilled may be called for. Surface treated high-speed steel drills are built to withstand the high speeds needed to drill through stainless steel, hardened bronze and welded seams.

Drills designed for hard or difficult materials (heat treated steels, nickel alloys, or titanium) feature custom points that can make it easier to start the hole without walking. Flute shape and margin width are specific to the more difficult materials. Surface treatments or coatings are almost always used to extend tool life.

Straight shank drills can efficiently drill through thin or stacked materials common in aircraft or aerospace jobs often use short wide flutes, wider margins and split points for exact starting. Similarly, versatile step drills have graduated diameters, allowing one bit to drill shallow holes of various diameters. These are often used on sheet metal to enlarge pilot holes to their desired width.

Using drills designed for special production purposes will:

increase their useful life
reduce waste

Bit by Bit: A Guide to Selecting the Right Drill

Standard Bits

Specialized Bits

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