Drill Bit Sizes
Selecting the correct drill bit size is important for proper fastener fit, tapping, and hole accuracy in FRC fabrication.
Common FRC Drill Bit Sizes
| Drill Bit | Common Use |
|---|---|
| #43 (0.089") | Tap drill for 4-40 |
| #36 (0.106") | Tap drill for 6-32 |
| #21 (0.159") | Tap drill for 10-32 |
| #7 (0.201") | Tap drill for 1/4-20 |
| 1/8" | Rivets and small hardware |
| 3/16" | Large rivets |
| 13/64" | Clearance hole for 10-32 |
| 17/64" | Clearance hole for 1/4-20 |
Tap Drill vs. Clearance Drill
Tap Drill
A tap drill creates the correct size hole for cutting threads with a tap.
Example:
- A 10-32 screw uses a #21 drill bit before tapping.
Clearance Drill
A clearance hole allows a fastener to pass through freely.
Example:
- A 10-32 bolt typically uses a 13/64" clearance hole.
Best Practices
- Verify the required drill size before drilling.
- Use a center punch to prevent drill wandering.
- Deburr holes after drilling.
- Label commonly used bits to prevent mistakes.
Common Mistakes
- Using a clearance hole when tapping is required.
- Selecting the wrong drill bit size.
- Drilling oversized holes.
- Forgetting to deburr the finished hole.
Key Idea
Using the correct drill bit size ensures proper fastener fit, accurate hole placement, and reliable assemblies on an FRC robot.