The drilling procedure is a systematic process used in machining to create accurate holes in a workpiece. Following proper steps ensures precision, safety, and tool life.
In this article:
7 Steps in the Drilling Procedure
The drilling procedure follows a systematic sequence to ensure accuracy, safety, and good surface finish.
Below are the 7 standard steps used in manufacturing workshops and CNC/manual drilling operations.
1. Marking and Layout
Description:
- The exact hole location is marked on the workpiece.
- Done using:
- Steel rule
- Divider
- Surface plate
- Layout dye
Purpose:
- Ensures correct hole position
- Prevents misalignment
2. Center Punching
Description:
- A center punch is used to make a small indentation at the marked location.
Purpose:
- Prevents the drill bit from wandering
- Improves hole accuracy
3. Workpiece Clamping
Description:
- The workpiece is securely fixed using:
- Machine vice
- T-slot clamps
- Fixtures
Purpose:
- Prevents movement during drilling
- Ensures operator safety
4. Center Drilling (Spot Drilling)
Description:
- A center drill or spot drill is used to start the hole.
Purpose:
- Provides accurate hole entry
- Reduces drill deflection
- Improves tool life
5. Drilling (Rough Drilling)
Description:
- A twist drill is used to drill the hole to required depth.
- May be done in stages (peck drilling).
Purpose:
- Removes bulk material
- Forms the main hole
6. Finishing Operation (Reaming / Counterboring / Countersinking)
Description:
Depending on requirement:
- Reaming → Improves size accuracy & surface finish
- Counterboring → Enlarges top portion of hole
- Countersinking → Produces conical seat
- Tapping → Creates internal threads
Purpose:
- Achieves final dimensional accuracy
- Prepares hole for fasteners or assembly
7. Inspection and Deburring
Description:
- Hole size and position are checked using:
- Vernier caliper
- Plug gauge
- Micrometer
- Sharp edges are removed by deburring.
Purpose:
- Ensures quality control
- Improves safety and appearance
Summary Table
| Step No. | Step Name | Purpose |
|---|---|---|
| 1 | Marking & layout | Accurate hole location |
| 2 | Center punching | Prevent drill slip |
| 3 | Clamping | Safety & stability |
| 4 | Center drilling | Accurate start |
| 5 | Drilling | Hole formation |
| 6 | Finishing | Accuracy & fit |
| 7 | Inspection & deburring | Quality control |
Conclusion:
Drilling is done step by step—from marking the hole to checking its accuracy—to ensure a precise and safe hole.
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