Drill Bits

Common Bit Types

1. Brad-point bit: This is a fluted bit with a special spur on the tip, which inserts itself into wood and keeps the bit firmly in place, allowing you to drill a clean entry hole. Generally coated in titanium, brad-point bits remove waste efficiently and make speedy work of jobs requiring a high degree of detail.

2. Twist bit: This standard “kit” bit has a cutting point and, like the brad-point, is fluted to remove waste. Though by far the most common type in this discussion, the twist bit is actually meant to drill into metal at slow speeds; use it wisely in household DIYs.

3. Countersink bit: Designed to create a tapered pilot hole or countersink for flush screw heads, this guy can save you loads of time. Stock up!

4. Forstner bit: Boring precise, flat-bottomed holes in wood, Forstner bits create the cleanest finish you can get with holes greater than a half-inch, but they’re better suited for drill presses than hand drills, as they require considerable force to be applied when removing waste material.

5. Spade bit: Also called “paddle bits,” these are geared toward rough boring in wood. Since the cutters are so large, spade bits facilitate drilling large holes and are the right choice if you’re running wires, cables, or pipes that won’t be seen.

6. Hole saw: Used for making fairly large holes in sheet goods and other thin materials, hole saws work faster than Forstner bits, removing only the outer perimeter with their saw teeth (rather than the entire waste of the hole). Buy a quality mandrel and several sizes of hole saw to use on the same chuck hardware.

7. Countersink cutter: Occasionally necessary for atypical hardware (in cases where the countersink bit is inappropriate), this type of bit creates a steep chamfer for the purpose of countersinking hardware.

8. Sanding drum. Different from the other bits in this roundup in that it doesn’t produce a hole, the sanding drum is installed into a chuck to smooth out curves and other non-planar shapes at high speeds.

Which Bit Does the Job?

High-Speed Steel (HSS) - is a popular material good for drilling into soft steels as well as wood and plastic. It is an economical solution for most common drilling applications.

Cobalt (HSCO) - is considered an upgrade from HSS because it includes 5-8% Cobalt blended into the base material. This is a great option for drilling into harder steel as well as stainless steel grades.

Carbide (Carb) - is the hardest and most brittle of the drill bit materials. It is used mostly for production drilling where a high quality tool holder and equipment is used. It should not be used in hand drills or even drill presses. These drill bits are designed for the most demanding and hardest materials.

Bit Design Features:

• 118 degree Standard - found on most common drill types

• 135 degree Self Centering - this type will begin drilling faster, especially in stainless steel materials

Drill Point Lengths:

• Use the shortest drill bit for the job. Shorter bits are more accurate and because they'er more rigid they don't break as often. Shorter bits are also better in tighter, more confined spaces.

• Different lengths include: Screw Machine Length, Mechanics Length, Jobber Length, Taper Length, Taper Shank

Flute Design:

• Standard - This is the most common with 30 degrees

• Parabolic Design - The open design helps chip removal out of the hole. These are very effective in very soft materials like plastics and aluminums.

Drill Point Coatings:

• Black Oxide - (surface treatment) Helps reduce friction and increase chip flow. Not to be used on nonferrous materials.

• Bright - Not real finish, but polished to increase chip flow. For use on plastics, woods, and aluminum

• TiN - (titanium nitride, gold color) Can be run faster than uncoated drills and increased tool life.

• TiCN (titanium carbonitride, blue-grey color) Great for stainless steel, cast iron and aluminum. Harder and more wear-resistant than other coatings. TiALN (Titanium Aluminum Nitride, violet color) For use in high-alloy carbon steels, nickel based materials and titanium. Not used on aluminum.