Change gears charts for inch threading on the 7x mini-lathe Charts show gears combination and error %. In order to make inch threads on a mini-lathe with a metric leadscrew, additional 21, 55, 57 and 65 teeth gears are needed. When for B and C gears ANY is shown on tables, it means that B and C gears are only necessary as a idler gear. On these cases, use for B and C a pair of gears with the same teeth number and a suitable size to mesh with A and D. To calculate change-gears combination for threading on any lathe you can use the following formula: TPI = (B/A) x (D/C) x leadscrew pitch
Inch threading on lathes with metric 1.5mm pitch leadscrew Simplified chart For the mini-lathe banjo and with the original gear set plus 21, 55, 57 and 65 teeth gears. | THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 80 TPI
| 20 | 65
| 55
| 80
| 0.0606 | 80.048 | 72 TPI
| 40 | 55
| 21
| 65
| 0.0914 | - | 64 TPI
| 45 | 55
| 21
| 65
| 0.0923 | - | 56 TPI
| 35
| 65
| 45
| 80
| 0.1669 | 55.907 | 48 TPI
| 60 | 55
| 21
| 65
| 0.0924 | - | 44 TPI
| - | -
| -
| -
| - | -
| | 40 TPI | 30
| 60
| 55
| 65
| 0.0606 | 40.024 | 36 TPI
| 80 | 55
| 21
| 65
| 0.0928 | - | 32 TPI
| 50
| 65
| 55
| 80
| 0.0606 | 32.019 | 28 TPI
| 35
| 55
| 57
| 60
| 0.0355 | 28.010 | 24 TPI
| 50
| 60
| 55
| 65
| 0.0603 | 24.015 | 20 TPI
| 55
| 40
| 40
| 65
| 0.0606 | 20.012 | 18 TPI
| 50
| 45
| 55
| 65
| 0.0605 | 18.011 | 16 TPI
| 50
| 40
| 55
| 65
| 0.0606 | 16.010 | | 14 TPI | 57
| 30
| 35
| 55
| 0.0355 | 14.005 | | 12 TPI | 50
| 30
| 55
| 65
| 0.0603 | 12.007 | | 11 TPI | 50
| 30
| 60
| 65
| 0.0605 | 11.007 | 10 TPI
| -
| -
| -
| -
| - | - | 9 TPI
| -
| -
| -
| -
| - | - | 8 TPI
| 57
| 35
| 65
| 50
| 0.0225 | 7.998 |
Extended chartsMany of these combinations don't fit the mini-lathe banjo, though can be used with other banjo styles. | THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 80 TPI
| 20 | 65
| 55
| 80
| 0.0606 | 80.048 | | 80 TPI | 20
| 80
| 55
| 65
| 0.0606 | 80.048 | 80 TPI
| 55 | 65
| 20
| 80
| 0.0606 | 80.048 |
| THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 72 TPI
| 40 | 55
| 21
| 65
| 0.0914 | 72.067 | | 72 TPI | 40
| 65
| 21
| 55
| 0.0914 | 72.067 |
| THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 64 TPI
| 45 | 55
| 21
| 65
| 0.0923 | 64.060 | | 64 TPI | 45
| 65
| 21
| 55
| 0.0923 | 64.060 |
| THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 56 TPI
| 35
| 65
| 45
| 80
| 0.1669 | 55.907 | | 56 TPI | 35
| 80
| 45
| 65
| 0.1669 | 55.907 | | 56 TPI | 45
| 65
| 35
| 80
| 0.1669 | 55.907 | | 56 TPI | 45 | 80
| 35
| 65
| 0.1669 | 55.907 |
| THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 48 TPI
| 60 | 55
| 21
| 65
| 0.0924 | 48.045 | | 48 TPI | 60
| 65
| 21
| 55
| 0.0924 | 48.045 |
| THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 44 TPI
| 55 | 50
| 21
| 60
| 0.0399 | 43.983
| | 44 TPI | 55
| 60
| 21
| 50
| 0.0399 | 43.983 |
| THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 40 TPI
| 20
| 40
| 55
| 65
| 0.0606 | 40.024 | | 40 TPI | 20
| 65
| 55
| 40
| 0.0606 | 40.024 | | 40 TPI | 30
| 60
| 55
| 65
| 0.0606 | 40.024 | | 40 TPI | 30 | 65
| 55
| 60
| 0.0606 | 40.024 | | 40 TPI | 40
| 65
| 55
| 80
| 0.0606 | 40.024 | | 40 TPI | 40
| 80
| 55
| 65
| 0.0606 | 40.024 | | 40 TPI | 55
| 40
| 20
| 65
| 0.0606 | 40.024 | | 40 TPI | 55
| 60
| 30
| 65
| 0.0606 | 40.024 | | 40 TPI | 55
| 65
| 30
| 60
| 0.0606 | 40.024 | | 40 TPI | 55
| 65
| 40
| 80
| 0.0606 | 40.024 | 40 TPI
| 55 | 80
| 40
| 65
| 0.0606 | 40.024 |
| THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 36 TPI
| 80 | 55
| 21
| 65
| 0.0928 | 36.034 | | 36 TPI | 80
| 65
| 21
| 55
| 0.0928 | 36.034 |
| THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 32 TPI
| 50
| 65
| 55
| 80
| 0.0606 | 32.019 | | 32 TPI | 50
| 80
| 55
| 65
| 0.0606 | 32.019 | | 32 TPI | 55
| 65
| 50
| 80
| 0.0606 | 32.019 | | 32 TPI | 55 | 80
| 50
| 65
| 0.0606 | 32.019 |
| THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 28 TPI
| 35
| 55
| 57
| 60
| 0.0355 | 28.010 | | 28 TPI | 35
| 60
| 57
| 55
| 0.0355 | 28.010 | | 28 TPI | 57
| 55
| 35
| 60
| 0.0355 | 28.010 | | 28 TPI | 57 | 60
| 35
| 55
| 0.0355 | 28.010 |
| THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 24 TPI
| 50
| 60
| 55
| 65
| 0.0603 | 24.015 | | 24 TPI | 50
| 65
| 55
| 60
| 0.0603 | 24.015 | | 24 TPI | 55
| 60
| 50
| 65
| 0.0603 | 24.015 | | 24 TPI | 55 | 65
| 50
| 60
| 0.0603 | 24.015 |
| THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 20 TPI
| 55
| ANY
| ANY
| 65
| 0.0606 | 20.012 |
| THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 18 TPI
| 50
| 45
| 55
| 65
| 0.0605 | 18.011 | | 18 TPI | 50
| 65
| 55
| 45
| 0.0605 | 18.011 | | 18 TPI | 55
| 45
| 50
| 65
| 0.0605 | 18.011 | | 18 TPI | 55 | 65
| 50
| 45
| 0.0605 | 18.011 |
| THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 16 TPI
| 50
| 40
| 55
| 65
| 0.0606 | 16.010 | | 16 TPI | 50
| 65
| 55
| 40
| 0.0606 | 16.010 | | 16 TPI | 55
| 40
| 50
| 65
| 0.0606 | 16.010 | | 16 TPI | 55 | 65
| 50
| 40
| 0.0606 | 16.010 |
| THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 14 TPI
| 35
| 30
| 57
| 55
| 0.0355 | 14.005 | | 14 TPI | 35
| 55
| 57
| 30
| 0.0355 | 14.005 | | 14 TPI | 57
| 30
| 35
| 55
| 0.0355 | 14.005 | | 14 TPI | 57 | 55
| 35
| 30
| 0.0355 | 14.005 |
| THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 12 TPI
| 35
| 65
| 55
| 21
| 0.0603 | 12.007 | | 12 TPI | 35
| 21
| 55
| 65
| 0.0603 | 12.007 | | 12 TPI | 50
| 30
| 55
| 65
| 0.0603 | 12.007 | | 12 TPI | 50 | 65
| 55
| 30
| 0.0603 | 12.007 | | 12 TPI | 55
| 30
| 50
| 65
| 0.0603 | 12.007 | | 12 TPI | 55
| 65
| 50
| 30
| 0.0603 | 12.007 | | 12 TPI | 55
| 21
| 35
| 65
| 0.0603 | 12.007 |
| THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 11 TPI
| 35
| 65
| 60
| 21
| 0.0605 | 11.007 | | 11 TPI | 35
| 21
| 60
| 65
| 0.0605 | 11.007 | | 11 TPI | 40
| 20
| 50
| 65
| 0.0605 | 11.007 | | 11 TPI | 50 | 20
| 40
| 65
| 0.0605 | 11.007 | | 11 TPI | 50
| 30
| 60
| 65
| 0.0605 | 11.007 | | 11 TPI | 50
| 40
| 80
| 65
| 0.0605 | 11.007 | | 11 TPI | 50
| 65
| 60
| 30
| 0.0605 | 11.007 | | 11 TPI | 50
| 65
| 80
| 40
| 0.0605 | 11.007 | | 11 TPI | 60
| 30
| 50
| 65
| 0.0605 | 11.007 | | 11 TPI | 60
| 65
| 50
| 30
| 0.0605 | 11.007 | | 11 TPI | 60 | 21
| 35
| 65
| 0.0605 | 11.007 | | 11 TPI | 80
| 40
| 50
| 65
| 0.0605 | 11.007 | | 11 TPI | 80
| 65
| 50
| 40
| 0.0605 | 11.007 |
| THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 10 TPI
| 20
| 45
| 80
| 21
| 0.0125 | 10.001 | | 10 TPI | 20
| 21
| 80
| 45
| 0.0125 | 10.001 | | 10 TPI | 80
| 21
| 20
| 45
| 0.0125 | 10.001 |
| THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 9 TPI
| 45
| 57
| 50
| 21
| 0.0946 | 9.009 | | 9 TPI | 45
| 21
| 50
| 57
| 0.0946 | 9.009 | | 9 TPI | 50
| 21
| 45
| 57
| 0.0946 | 9.009 | | THREAD | A | B
| C
| D
| ERROR %
| REAL TPI
| 8 TPI
| 57
| 35
| 65
| 50
| 0.0225 | 7.998 | | 8 TPI | 57
| 50
| 65
| 35
| 0.0225 | 7.998 | | 8 TPI | 65
| 35
| 57
| 50
| 0.0225 | 7.998 | | 8 TPI | 65 | 50
| 57
| 35
| 0.0225 | 7.998 |
|
