Tapping Drill Size Chart for Thread Cutting Taps (Metric-Imperial Values)
For your convenience, we’ve compiled a simplified chart of tapping coarse and fine drill sizes.
We trust that the information below is self-explanatory and straightforward.
Thread Size | Pitch | Coarse Drill Size | Thread Size (mm) | Pitch (mm) | Drill Size (mm) | Drill Size (inch) | Thread Size | Coarse Drill | Fine Drill Size | |||
Metric (mm) | Metric (mm) | Metric (mm) | Decimal inches (~) | Fractional inches (~) | # | Metric (mm) | ||||||
M1.0 | 0.25 | 0.75 | 0.03 | #67 | M1.0 | 0.25 | 0.75 | 0.03 | M1 | 0.75 | --- | |
M1.2 | 0.25 | 0.95 | 0.037 | #61 | M1.2 | 0.25 | 0.95 | 0.037 | M1.2 | 0.95 | --- | |
M1.4 | 0.30 | 1.10 | 0.043 | #55 | M1.4 | 0.30 | 1.10 | 0.043 | M1.4 | 1.1 | --- | |
M1.6 | 0.35 | 1.25 | 0.049 | 3/64 | M1.6 | 0.35 | 1.25 | 0.049 | M1.6 | 1.25 | --- | |
M1.8 | 0.35 | 1.45 | 0.059 | #53 | M1.8 | 0.35 | 1.45 | 0.057 | M1.8 | 1.45 | --- | |
M2.0 | 0.40 | 1.60 | 0.063 | #52 | M2.0 | 0.40 | 1.60 | 0.063 | M2 | 1.6 | 1.75 | |
M2.2 | 0.45 | 1.75 | 0.070 | #50 | M2.2 | 0.45 | 1.75 | 0.069 | --- | --- | --- | |
M2.5 | 0.45 | 2.05 | 0.081 | #46 | M2.5 | 0.45 | 2.05 | 0.081 | M2.5 | 2.05 | 2.15 | |
M3.0 | 0.50 | 2.50 | 0.098 | #37 | M3.0 | 0.50 | 2.50 | 0.098 | M3 | 2.5 | 2.65 | |
M3.5 | 0.60 | 2.90 | 0.114 | #32 | M3.5 | 0.60 | 2.90 | 0.114 | M3.5 | 2.9 | --- | |
M4.0 | 0.70 | 3.30 | 0.130 | #29 | M4.0 | 0.70 | 3.30 | 0.13 | M4 | 3.3 | 3.5 | |
M4.5 | 0.75 | 3.70 | 0.146 | #25 | M4.5 | 0.75 | 3.70 | 0.146 | --- | --- | --- | |
M5.0 | 0.80 | 4.20 | 0.165 | #16 | M5.0 | 0.80 | 4.20 | 0.165 | M5 | 4.2 | 4.5 | |
M6.0 | 1.00 | 5.00 | 0.197 | #8 | M6.0 | 1.00 | 5.00 | 0.197 | M6 | 5 | 5.3 | |
M7.0 | 1.00 | 6.00 | 0.236 | B | --- | --- | M7 | 6 | 6.25 | |||
M8.0 | 1.25 | 6.75 | 0.268 | H | M8.0 | 1.25 | 6.80 | 0.268 | M8 | 6.8 | 7 | |
M9.0 | 1.25 | 7.75 | 0.305 | #31 | --- | --- | --- | --- | --- | |||
M10.0 | 1.50 | 8.50 | 0.335 | R | M10.0 | 1.50 | 8.50 | 0.335 | M10 | 8.5 | 9 | |
M11.0 | 1.50 | 9.50 | 0.374 | #9 | --- | --- | --- | --- | --- | |||
M12.0 | 1.75 | 10.25 | 0.402 | Y | M12.0 | 1.75 | 10.20 | 0.402 | M12 | 10.2 | 10.5 | |
M14.0 | 2.00 | 12.00 | 0.472 | 15/32 | M14.0 | 2.00 | 12.00 | 0.472 | M14 | 12 | 12.5 | |
M16.0 | 2.00 | 14.00 | 0.551 | 9/16 | M16.0 | 2.00 | 14.00 | 0.551 | M16 | 14 | 14.5 | |
M18.0 | 2.50 | 15.50 | 0.61 | 39/64 | M18.0 | 2.50 | 15.50 | 0.61 | M18 | 15.5 | 16.5 | |
M20.0 | 2.50 | 17.50 | 0.689 | 11/16 | M20.0 | 2.50 | 17.50 | 0.689 | M20 | 17.5 | 18.5 | |
M22.0 | 2.50 | 19.50 | 0.768 | 49/64 | M22.0 | 2.50 | 19.50 | 0.768 | M22 | 19.5 | 20.5 | |
M24.0 | 3.00 | 21.00 | 0.827 | 53/64 | M24.0 | 3.00 | 21.00 | 0.827 | M24 | 21 | 22 | |
M27.0 | 3.00 | 24.00 | 0.945 | 61/64 | M27.0 | 3.00 | 24.00 | 0.945 | M27 | 24 | --- | |
M30.0 | 3.50 | 26.50 | 1.043 | 1-1/16 | M30.0 | 3.50 | 26.50 | 1.043 | M30 | 26.5 | --- | |
M33.0 | 3.50 | 29.00 | 1.161 | 1-1/8 | M33.0 | 3.50 | 29.50 | 1.161 | M33 | --- | --- | |
M36.0 | 4.00 | 32.00 | 1.26 | 1-1/4 | M36.0 | 4.00 | 32.00 | 1.26 | M36 | 32 | --- | |
M39.0 | 4.00 | 35.00 | 1-3/8 | --- | --- | M39 | --- | --- | ||||
M42.0 | 4.50 | 37.50 | 1.476 | 1-1/2 | M42.0 | 4.50 | 37.50 | 1.476 | M42 | 37.5 | --- | |
M45.0 | 4.50 | 40.50 | 1.594 | 1-5/8 | M45.0 | 4.50 | 40.50 | 1.594 | M45 | 40.5 | --- | |
M48.0 | 5.00 | 43.00 | 1.693 | 1-3/4 | M48.0 | 5.00 | 43.00 | 1.693 | M48 | 43 | --- | |
M50.0 | 5.00 | 45.50 | 1.772 | 1-7/8 | M50.0 | 5.00 | 45.00 | 1.772 | M50 | --- | 48.5 |
Table values compiled from:
- Engineers Black Book – Third Edition (Metric)
- Sutton Tools Drill Size & Decimal Equivalent Chart
- Allied Machine Tap Drill Chart
- Fractory Metric & Metric Fine Tap Drill Chart
- Newman Tools - ISO Metric Coarse Pitch, Fine Pitch and Extra Fine Pitch Taps
Notes:
- This table covers a range of sizes but might not include all available thread sizes.
- Not all metric tapping drill bits have imperial equivalents, and vice versa.
- Fine thread sizes are less common than coarse threads.
- Coarse or fine threads require different drill sizes.
- Some metric values are close enough to essentially have the same imperial counterpart.
- Some values are rounded to their nearest thousandth millimeters and ten-thousandth decimal inches.
Considerations:
- The choice of drill size and thread depth can vary significantly based on the material being tapped (eg steel, aluminium, plastic).
- The desired thread depth affects the necessary clearance for the tap.
- The tightness of the thread (close, medium, or free fit) influences the drill size.
- Different tap types (taper, plug, bottoming) require slightly different drill sizes.
- The Engineers Black Book’s section in calculation of tapping drill sizes advises to “use a good cutting oil or lubricant rather than coolant for fluteless (thread forming) taps”.
Important:
- Always consult a detailed tap drill chart for accurate and precise drill size selection.
You may want to consider getting the Engineers Black Book (3rd Edition – Metric) for more complete information, specifically:
- Calculation, formulas and examples of tapping drill size:
- For thread cutting taps (tapping drill size in metric and inches, thread percentage in metric)
- For fluteless taps (tapping drill size in metric and inches)
- Complete and detailed tapping drill sizes (screw size, major/minor/ effective diameters, tap and clearance drill sizes etc) for thread cutting taps in:
- ISO metric coarse, metric fine, metric conduit, metric special pitches and metric sparkplug
- UNC (Unified National Coarse)
- UNF (Unified National Fine)
- UNEF (Unified National Extra Fine)
- BA (British Association)
- BSW (British Standard Whitworth)
- BSF (British Standard Fine)
- BSP (British Standard Pipe)
- BSPT (British Standard Pipe Taper)
- PG (Panzerrohr-Gewinde)
- NPT (American National Pipe Taper)