Key Factors in Choosing Precision Threading Drill Bits Alternatively If Emphasizing Industryapplication precision Threading Essential Drill Bit Selection Tips

2025-11-11

Choosing the correct drill size for threading operations is critical for machining quality. An oversized drill compromises thread strength, while an undersized one increases tapping resistance and may cause tap breakage. This reference guide provides precise drill size recommendations for both imperial and metric thread standards.

Imperial Thread (Inch) Tap Drill Reference

Imperial threads, widely used in North America, require careful drill selection. The following table lists thread sizes from smallest to largest with corresponding drill sizes in fractional, number, and letter designations:

Thread Size	Fractional	Number/Letter	Decimal (inch)
0-80 NF	3/64"	-	0.0469"
1-64 NC	-	#53	0.0595"
1-72 NF	1/16"	#53	0.0595"
2-56 NC	-	#50	0.0700"
3-48 NC	5/64"	#47	0.0785"
4-40 NC	3/32"	#43	0.0890"
6-32 NC	7/64"	#35	0.1100"
8-32 NC	-	#29	0.1360"
10-24 NC	5/32"	#25	0.1495"
1/4-20 NC	13/64"	#7	0.2010"
5/16-18 NC	17/64"	F	0.2570"
3/8-16 NC	5/16"	-	0.3125"
1/2-13 NC	27/64"	-	0.4219"

Metric Thread (Millimeter) Tap Drill Reference

Common in Europe and Asia, metric threads follow a different sizing system. Drill sizes are provided in both millimeters and inches for convenience:

Thread Size	Recommended Drill Size (mm)	Recommended Drill Size (inch)
3mm-0.60mm	2.5mm	0.0984"
4mm-0.70mm	3.4mm	0.1338"
5mm-0.80mm	4.3mm	0.1693"
6mm-1.00mm	5.2mm	0.2047"
8mm-1.25mm	6.9mm	0.2716"
10mm-1.50mm	8.7mm	0.3425"
12mm-1.75mm	10.5mm	0.4133"
14mm-2.00mm	12.2mm	0.4803"
16mm-2.00mm	14.2mm	0.5590"
20mm-2.50mm	17.8mm	0.7008"

Specialty Thread Considerations

Special applications like spark plug threads require specific drill sizes, which are noted in the full reference tables with appropriate markings.

Operational Guidelines

Material Selection: Match drill bit material to workpiece hardness (e.g., cobalt drills for hardened materials)
Cooling: Always use appropriate cutting fluids to reduce heat and extend tool life
Speed Control: Adjust RPM based on material and drill size specifications
Feed Rate: Maintain optimal feed pressure to prevent tool breakage
Maintenance: Regularly inspect tools for wear and replace as needed

This reference guide serves as an essential tool for machinists and engineers, ensuring proper thread hole preparation for optimal threading results across various material types and applications.

Bi Metal Hole Saw

Carbon Steel Hole Saw

Tungsten Carbide Gritted Hole Saw

Vacuum Brazing Diamond Hole Saw

Multi Blade Hole Saw

TCT Hole Saw

Hole Saw Accessories

Tungsten Carbide File

Diamond Milling Cutter Chamfer Tools

Adjustable Circle Hole Cutter

Other Tools

Multi Tool Blades

Wood Flat Bit

Screw Extractor

Bi Metal Hole Saw

Carbon Steel Hole Saw

Tungsten Carbide Gritted Hole Saw

Vacuum Brazing Diamond Hole Saw

Multi Blade Hole Saw

TCT Hole Saw

Hole Saw Accessories

Tungsten Carbide File

Diamond Milling Cutter Chamfer Tools

Adjustable Circle Hole Cutter

Other Tools

Multi Tool Blades

Wood Flat Bit

Screw Extractor

Key Factors in Choosing Precision Threading Drill Bits Alternatively If Emphasizing Industryapplication precision Threading Essential Drill Bit Selection Tips

Key Factors in Choosing Precision Threading Drill Bits Alternatively If Emphasizing Industryapplication precision Threading Essential Drill Bit Selection Tips