Different tools are used for performing different types of operations. The most commonly used tools in a drilling machine are

  1. Drill
  2. Reamer
  3. Counterbore
  4. Countersink
  5. Tap

Drill

A drill is a tool used to originate a hole in a solid material. A helical groove known as ‘flute’ is cut along the length of the drill.

Different types of drills are

  1. Flat Drill
  2. Straight fluted drill
  3. Twist drill
  4. Centre drill

Twist drills are the type generally used in shop work. They are made of High speed steel (HSS) or High carbon steel.

There are two types of twist drills namely (i) Straight shank twist drill and (ii) Taper shank twist drill. The diameter of the straight shank drill ranges from 2 to 16mm. Taper shanks are provided on drills of larger diameter.

Reamer

The tool used for enlarging and finishing a previously drilled hole is known as a reamer. It is a multi tooth cutter and removes smaller amount of material. It gives a better fnish and accurate dimension.

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Counterbore

A Counterbore is a multi tooth cutting tool used for enlarging the top of the previously machined hole. It has three or four cutting teeth.

The flutes on them may be straight or helical. Straight fluted tools are used for machining softer materials like brass and aluminium and for short depth of cut. Helical fluted counterbores are used for longer holes.

Countersink

A countersink has cutting edges on its conical surfaces. It has a similar construction of a counterbore except for the angle of the cutting edges.The angle of countersinks will generally be 60°, 82° or 90°. It is used for enlarging the top of the holes conically.

Tap

A tap has threads like a bolt.It has three to four flutes cut across the threads. It can cut threads on the inside of a hole. The flutes on the threads form the cutting edges. It is a multi point cutting tool. It will dig into the walls of the hole as the lower part of the tap is slightly tapered. The shank of the tap is square shaped to enable it to be held by a tap wrench.

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