This professional drill bit to tap chart provides standard recommended drill bit sizes for all common metric, UNC, UNF, and NPT threads. All values follow industrial standard 75% thread engagement, ideal for general machining, metalworking, and DIY tapping projects. This tap and drill table covers the most frequently used thread specifications for accurate, clean threading results.
Key Formula: Tap Drill Size = Thread Major Diameter – Thread Pitch
Standard Default: 75% thread engagement (optimal for steel, iron, and most metal materials)
Material Tips: Use a slightly smaller drill bit for soft materials (aluminum, plastic, copper); use a slightly larger drill bit for hard materials (stainless steel, hardened steel) to prevent tap breakage.
Metric Thread Tap Drill Bit Chart (ISO Standard M-Series)
Standard metric coarse and fine thread drill bit size chart for tapping, widely used in industrial machinery and hardware assembly.
| Thread Size | Thread Pitch (mm) | Standard Tap Drill Size (mm) | Thread Type |
|---|---|---|---|
| M2 | 0.4 | 1.6 | Coarse |
| M2.5 | 0.45 | 2.05 | Coarse |
| M3 | 0.5 | 2.5 | Coarse |
| M4 | 0.7 | 3.3 | Coarse |
| M5 | 0.8 | 4.2 | Coarse |
| M6 | 1.0 | 5.0 | Coarse |
| M8 | 1.25 | 6.8 | Coarse |
| M8×1.0 | 1.0 | 7.0 | Fine |
| M10 | 1.5 | 8.5 | Coarse |
| M10×1.25 | 1.25 | 8.8 | Fine |
| M12 | 1.75 | 10.2 | Coarse |
| M12×1.5 | 1.5 | 10.5 | Fine |
| M14 | 2.0 | 12.0 | Coarse |
| M16 | 2.0 | 14.0 | Coarse |
| M20 | 2.5 | 17.5 | Coarse |
UNC Coarse Thread Drill Bit to Tap Chart (Imperial Standard)
UNC (Unified National Coarse) thread drill bit size chart for general-purpose imperial tapping, high tolerance and strong thread fastening.
| UNC Thread Size | TPI (Threads Per Inch) | Standard Tap Drill Size | Drill Diameter (Inch) | Drill Diameter (mm) |
|---|---|---|---|---|
| #4-40 UNC | 40 | #43 | 0.0890 | 2.26 |
| #6-32 UNC | 32 | #36 | 0.1065 | 2.71 |
| #8-32 UNC | 32 | #29 | 0.1360 | 3.45 |
| #10-24 UNC | 24 | #25 | 0.1495 | 3.80 |
| 1/4-20 UNC | 20 | #7 | 0.2010 | 5.11 |
| 5/16-18 UNC | 18 | F | 0.2570 | 6.53 |
| 3/8-16 UNC | 16 | 5/16″ | 0.3125 | 7.94 |
| 1/2-13 UNC | 13 | 27/64″ | 0.4219 | 10.72 |
UNF Fine Thread Tap and Drill Table (Imperial Standard)
UNF (Unified National Fine) drill bit size chart for precision tapping, featuring tighter thread pitch and better vibration resistance for precision machinery.
| UNF Thread Size | TPI (Threads Per Inch) | Standard Tap Drill Size | Drill Diameter (Inch) | Drill Diameter (mm) |
|---|---|---|---|---|
| #4-48 UNF | 48 | #42 | 0.0935 | 2.37 |
| #6-40 UNF | 40 | #33 | 0.1130 | 2.87 |
| #8-36 UNF | 36 | #29 | 0.1360 | 3.45 |
| #10-32 UNF | 32 | #21 | 0.1590 | 4.04 |
| 1/4-28 UNF | 28 | #3 | 0.2130 | 5.41 |
| 5/16-24 UNF | 24 | I | 0.2720 | 6.91 |
| 3/8-24 UNF | 24 | Q | 0.3320 | 8.43 |
| 1/2-20 UNF | 20 | 17/32″ | 0.5313 | 13.49 |
NPT Taper Pipe Thread Drill Bit Size Chart
Standard NPT taper pipe thread drill bit to tap chart for hydraulic, pneumatic and pipeline threading applications.
| NPT Thread Size | TPI | Standard Tap Drill Size | Drill Diameter (Inch) | Drill Diameter (mm) |
|---|---|---|---|---|
| 1/16-27 NPT | 27 | Letter C | 0.2420 | 6.15 |
| 1/8-27 NPT | 27 | Letter R | 0.3390 | 8.61 |
| 1/4-18 NPT | 18 | 7/16″ | 0.4375 | 11.11 |
| 3/8-18 NPT | 18 | 37/64″ | 0.5781 | 14.68 |
| 1/2-14 NPT | 14 | 23/32″ | 0.7188 | 18.26 |
