Types of Drilling tools -LearnMech

Drilling tools

Different types of drills are properly used for various applications depending upon work material, tool material, depth and diameter of the holes.

Read More : Classification/Types Of Drilling Machine use In Mechanical Workshop

General purpose drills may be classified as:

According to material:

  1. High speed steel – most common.
  2. Cemented carbides.
  3. Without or with coating.
  4. In the form of brazed, clamped or solid.
Types of Drilling tools
Types of Drilling tools

According to size:

  • Large twist drills of diameter around 40 mm.
  • Micro drills of diameter 25 μm to 500 μm.
  • Medium range diameter ranges between 3 mm to 25 mm (most widely used).

According to number of flutes:

  • Two fluted – most common.
  • Single flute – e.g., gun drill (robust).
  • Three or four flutes – called slot drill.

According to helix angle of the flutes:

  1. Usual: 200 to 350 – most common.
  2. Large helix: 450 to 600 – suitable for deep holes and softer work materials.
  3. Small helix: for harder / stronger materials.
  4. Zero helix: spade drills for high production drilling micro-drilling and hard work materials.

According to length to diameter ratio:

  • Deep hole drill; e.g. crank shaft drill, gun drill etc.
  • General type: L/φ ≅ 6 to 10.
  • Small length: e.g. centre drill.

According to shank:

  • Straight shank – small size drill being held in drill chuck.
  • Taper shank – medium to large size drills being fitted into the spindle nose directly or through taper sockets and sleeves.

According to specific applications:

  1. Centre drill [Fig. 3.126 (a)] for small axial holes with 600 taper ends to hold the lathe centre.
  2. Step drill and sub land drill [Fig. 3.126 (b and c)] for small holes with 2 or 3 steps.
  3. Ejector drill for high speed drilling of large diameter holes.
  4. Taper drill for batch production.
  5. Trepanning tool [Fig. 3.126 (g)] for large holes in soft materials.
Horizontal Reciprocating Sand Sieving Machine Mechanical Project
Basic QAQC Interview Questions and answers For Quality Engineers
Spread the love