a. Drilling Operation
Drilling is the operation of creating a cylindrical hole in a solid material using a rotating cutting tool called a drill bit.
- The drill rotates and cuts into the material to create a new hole.
- A center punch mark is made first to guide the drill.
- The drill bit is mounted on the spindle of the drilling machine.
- The workpiece is held on the table or fixture.
Sketch Description:
- Drill bit mounted vertically in the spindle.
- Workpiece clamped on the table.
- Drill bit penetrates and removes material to form the hole.
Purpose: To make a new hole of a required diameter and depth.
b. Boring Operation
Boring is the operation of enlarging an existing drilled hole using a single-point cutting tool.
- It’s used when higher accuracy and diameter enlargement are needed.
- It also improves the roundness and alignment of the hole.
- Carried out on a drilling machine or boring machine.
Sketch Description:
- Existing hole is enlarged using a boring bar (a long tool with a single cutter).
- The bar rotates to remove inner material, making the hole larger and more precise.
Purpose: To enlarge and finish an existing hole to accurate dimensions.
c. Reaming Operation
Reaming is the operation of finishing and sizing an existing hole to a high level of accuracy.
- A reamer, which has multiple cutting edges, is used.
- The hole is pre-drilled slightly smaller, and the reamer enlarges it to final size.
- The reaming speed is half of drilling speed for accuracy.
Sketch Description:
- A fluted reamer rotates and enters an existing hole.
- Very little material is removed (~0.125 mm).
- Produces a smooth and dimensionally accurate surface.
Purpose: To improve surface finish and bring the hole to an exact final size.