Mini Lathe Change Gear Calculator
Know what you can cut, and how precisely!
Example combinations for common thread pitches
Metric coarse threads
| Name | A | B | C | D | P | |
|---|---|---|---|---|---|---|
| M1.6 | 20 | 40 | 35 | 80 | 0.350 mm/rev | |
| M2 | 20 | 40 | 40 | 80 | 0.400 mm/rev | |
| M2.5 | 30 | 60 | 45 | 80 | 0.450 mm/rev | |
| M3 | 30 | 60 | 50 | 80 | 0.500 mm/rev | |
| M4 | 30 | 40 | 35 | 60 | 0.700 mm/rev | |
| M5 | 20 | 80 | 80 | 40 | 0.800 mm/rev | |
| M6 | 30 | 40 | 50 | 60 | 1.000 mm/rev | |
| M8 | 40 | 45 | 50 | 57 | 1.248 mm/rev | |
| M10 | 45 | 30 | 50 | 80 | 1.500 mm/rev | |
| M12 | 35 | 40 | 50 | 40 | 1.750 mm/rev | |
| M14 | 45 | 30 | 50 | 60 | 2.000 mm/rev | |
| M16 | 45 | 30 | 50 | 60 | 2.000 mm/rev | |
| M20 | 50 | 57 | 80 | 45 | 2.495 mm/rev | |
| M24 | 45 | 30 | 50 | 40 | 3.000 mm/rev | |
| M27 | 45 | 30 | 50 | 40 | 3.000 mm/rev | |
| M30 | 80 | 45 | 80 | 65 | 3.501 mm/rev | |
| M33 | 80 | 45 | 80 | 65 | 3.501 mm/rev | |
| M36 | 50 | 30 | 60 | 40 | 4.000 mm/rev | |
| M39 | 50 | 30 | 60 | 40 | 4.000 mm/rev | |
Metric fine threads
| Name | A | B | C | D | P | |
|---|---|---|---|---|---|---|
| M8 Fine | 30 | 40 | 50 | 60 | 1.000 mm/rev | |
| M10 Fine | 40 | 45 | 50 | 57 | 1.248 mm/rev | |
| M12 Fine | 45 | 30 | 50 | 80 | 1.500 mm/rev | |
| M16 Fine | 45 | 30 | 50 | 80 | 1.500 mm/rev | |
| M20 Fine | 45 | 30 | 50 | 80 | 1.500 mm/rev | |
| M24 Fine | 45 | 30 | 50 | 60 | 2.000 mm/rev | |
| M30 Fine | 45 | 30 | 50 | 60 | 2.000 mm/rev | |
| M36 Fine | 45 | 30 | 50 | 40 | 3.000 mm/rev | |
| M39 Fine | 45 | 30 | 50 | 40 | 3.000 mm/rev | |
Metric super fine threads
| Name | A | B | C | D | P | |
|---|---|---|---|---|---|---|
| M10 Super fine | 30 | 40 | 50 | 60 | 1.000 mm/rev | |
| M12 Super fine | 40 | 45 | 50 | 57 | 1.248 mm/rev | |
UNC threads
| Name | A | B | C | D | P | |
|---|---|---|---|---|---|---|
| UNC #2 | 30 | 57 | 35 | 65 | 56.016 TPI | |
| UNC #4 | 35 | 55 | 50 | 80 | 39.914 TPI | |
| UNC #5 | 35 | 55 | 50 | 80 | 39.914 TPI | |
| UNC 1/4 | 35 | 40 | 50 | 55 | 19.957 TPI | |
| UNC 5/16 | 45 | 35 | 55 | 80 | 17.960 TPI | |
| UNC 3/8 | 55 | 45 | 65 | 80 | 15.986 TPI | |
| UNC 7/16 | 80 | 45 | 35 | 55 | 14.032 TPI | |
| UNC 1/2 | 45 | 35 | 57 | 60 | 12.997 TPI | |
| UNC 9/16 | 57 | 35 | 65 | 80 | 11.997 TPI | |
| UNC 5/8 | 40 | 45 | 65 | 40 | 10.990 TPI | |
| UNC 3/4 | 55 | 45 | 65 | 50 | 9.991 TPI | |
| UNC 7/8 | 57 | 35 | 65 | 60 | 8.998 TPI | |
| UNC 1 | 55 | 30 | 65 | 60 | 7.993 TPI | |
| UNC 1 1/8 | 55 | 35 | 65 | 45 | 6.994 TPI | |
| UNC 1 1/4 | 55 | 35 | 65 | 45 | 6.994 TPI | |
| UNC 1 1/2 | 57 | 35 | 65 | 40 | 5.999 TPI | |
UNF threads
| Name | A | B | C | D | P | |
|---|---|---|---|---|---|---|
| UNF #3 | 30 | 57 | 35 | 65 | 56.016 TPI | |
| UNF #5 | 20 | 80 | 65 | 45 | 43.962 TPI | |
| UNF #6 | 35 | 55 | 50 | 80 | 39.914 TPI | |
| UNF #8 | 35 | 55 | 45 | 65 | 36.034 TPI | |
| UNF #12 | 35 | 57 | 60 | 65 | 28.008 TPI | |
| UNF 1/4 | 35 | 57 | 60 | 65 | 28.008 TPI | |
| UNF 7/16 | 35 | 40 | 50 | 55 | 19.957 TPI | |
| UNF 1/2 | 35 | 40 | 50 | 55 | 19.957 TPI | |
| UNF 9/16 | 45 | 35 | 55 | 80 | 17.960 TPI | |
| UNF 5/8 | 45 | 35 | 55 | 80 | 17.960 TPI | |
| UNF 3/4 | 55 | 45 | 65 | 80 | 15.986 TPI | |
| UNF 7/8 | 80 | 45 | 35 | 55 | 14.032 TPI | |
| UNF 1 | 80 | 45 | 35 | 55 | 14.032 TPI | |
| UNF 1 1/8 | 57 | 35 | 65 | 80 | 11.997 TPI | |
| UNF 1 1/4 | 40 | 45 | 65 | 40 | 10.990 TPI | |
| UNF 1 1/2 | 55 | 45 | 65 | 50 | 9.991 TPI | |
British pipe threads
| Name | A | B | C | D | P | |
|---|---|---|---|---|---|---|
| G 1/8 | 35 | 57 | 60 | 65 | 28.008 TPI | |
| G 1/4 | 30 | 40 | 50 | 45 | 19.050 TPI | |
| G 3/8 | 30 | 40 | 50 | 45 | 19.050 TPI | |
| G 1/2 | 80 | 45 | 35 | 55 | 14.032 TPI | |
| G 3/4 | 80 | 45 | 35 | 55 | 14.032 TPI | |
| G 1 | 40 | 45 | 65 | 40 | 10.990 TPI | |
| G 1 1/4 | 40 | 45 | 65 | 40 | 10.990 TPI | |
| G 1 1/2 | 40 | 45 | 65 | 40 | 10.990 TPI | |