Drill Bits

There are many different types of drill bits, designed for drilling different materials or for use in different types of machine e.g. hand drill or power drill.

Notes

• Care should be taken when drilling plastics as they may tend to melt, in this situation the speed should be reduced. Clearing the flutes on a regular basis may also help reduce the problem of chippings welding to the item being drill or the item over-heating.
• When drilling brass it helps to reduce the rake on the cutting edge of the drill to zero. Otherwise the drill may have a tendency to pull itself through the item.
• If the hole is larger than the drill it is most probable that the two cutting angles are not identical. This will throw the drill point out of centre and result in it wobbling.
• If the drill point wears quickly this may be due to speed being too high or the cutting angle being different on each side of the drill resulting in one side doing all of the work.
• If drilling a large hole it is good practise to drill a small hole first as a guide.

Centre Drill

A combined countersink and drill used to prepare work for mounting centres.

Flat Wood Drill

A wood drill that has a centre point to locate the drill and flats that bore the hole.

Twist Drill

A commonly used metal-cutting drill, usually made with two flutes running around the body.

See also: Blind Hole, Carpenters Brace, Centre Drill, Chuck, Drill Gauge, Drill Jig, Drill Press, Flat Wood Drill, Flute, Letter Drills, Lip of a Drill, Number Drills, Pilot Hole, Twist Drill.