How to Choose Drill Bits

Choosing the proper drill bit before drilling a hole can mean the difference between a hole or a broken drill bit, or it might mean having a clean hole with smooth edges instead of damaging the material being drilled.

Instructions

1. Determine what type of material you will be drilling into. Is it wood, soft metal, steel, concrete, stone, tile or glass? The material makes all the difference and there are drill bits for just about anything.

2. Determine the type of hole to be drilled. For some material types, there are few choices on drill bits. For others, the type of hole to be drilled determines the type of bit. Will it be a small hole in wood to pre-drill for a screw, or is it a two inch wide hole in concrete for a drain pipe?

3. Choose your bit for wood, thick plastics and similar materials. Standard wood bits make clean holes fairly quickly. They are good for pre-drilling screws and holes for bolts. Larger holes in rough lumber can be handled with spade bits. For larger holes in finished wood, use a forstner bit.

4. Choose titanium, cobalt or carbide bits for drilling in soft metals. They cost a little more than a wood bit, but will last a lot longer when drilling into metal. Holes larger than 1/2 inch should be bored with a mill.

5. Choose a carbide or cobalt bit for steel. Small holes can be drilled fairly easily, but larger ones require special equipment.

6. Drill holes in concrete and stone with a hammer drill and corresponding bit. The hammer drill pounds on the bit as it turns, shattering the stone and concrete beneath the bit. Standard masonry bits can also be purchased. They are slower than hammer bits, but leave a cleaner hole. Hammer bits are available up to an inch and half in size. Larger holes up to five inches can be drilled with a coring machine and bit.

7. Purchase diamond coated bits for cutting glass and tile. These are special bits that look a little like a point with wings. Holes up to 1/2 inch may be bored using these bits. Larger holes require a pilot hole to be drilled, usually 1/8 inch. Then a special cutting bit that scribes a circle is used. Without a drill press or mill, these holes are best left to glass shops.

Tips & Warnings

• Never lean on a drill or try to force the bit through. Let the bit do the work; it will last longer and so will your drill

• Always wear safety glasses or goggles when drilling. They will protect you from a broken drill bit or flying piece of material.

References

• Drill Bits
• Drill selection for other materials