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.