Metric Threading With Six Gears

[Bill_Cook]

Although I work in inches, and have been able to manipulate metric bolts to good affect, it would be nice to have metric threading ability. My Sheldon has the metric change gear tag on it but no gears. What a tease! After staring at the metric and quick change tags for some time it became apparent that the tumbler lever could be used for some threads even though the the metric tag didn't show it.

Here's what I came up with to produce the common pitches. - 1, 1.25, 1.5, 1.75, 2, 2.5, and 3mm - 3.5, 4, 5, 6, and 7mm would be a bonus.

Compound gear 127/110t - (Gear Cutter #2)

Gear on box 44t - (Gear Cutter #3)

Stud Gears with tumbler at far left position (4, 8, 16TPI) as specified in Transposing Chart:

40t - 5.000 2.500 1.250* - (Gear Cutter #3)

48t - 6.000 3.000 1.500# - (Gear Cutter #3)

56t - 7.000 3.500 1.750 - (Gear Cutter #2)


*40t* - 4.000 2.000 1.000 With tumbler in 3rd position from left (5, 10, 20TPI). This position turns the lead screw 4/5 the speed it would turn in the far left (4, 8, 16TPI) and will move the carriage 4/5 the distance.

OR

#48t# - 4.000 2.000 1.000 With tumbler in 6th position from left (6, 12, 24TPI). This position turns the lead screw 4/6 or 2/3 the speed it would turn in the far left (4, 8, 16TPI).


Six gears made with two gear cutters. Can't help but think this would work with some other makes having the same quick change layout and an eight TPI lead screw. On the Sheldon, the metric gears can be mounted on the stock banjo.
____

With 3 more gears and one more gear cutter .750, .500, and .250mm threads can be cut.

2 - 80t - compound gear and gear on box - (Gear Cutter #2)

Stud Gear with tumbler at far left position (4, 8, 16TPI) as specified in Transposing Chart:

30t - 1.500 0.750 0.375 - (Gear Cutter #4)

30t 1.200 0.600 0.300 With tumbler in 3rd position from left (5, 10, 20TPI).

30t 1.000 0.500 0.250 With tumbler in 6th position from left (6, 12, 24TPI).