# Thread: Metric Gears for the Round Dial 10EE

1. Peter and I have been discussing the possibilities of adapting the solution for metric gears for the square dial to a Round Dial gear train on and off for the last few months. We collaborated in the following solution, which actually turns out to be quite simple, since no transposition gears are needed.

The square dial and round dial gear trains have one major difference and some similarities. Both have a stud gear and a box gear and two idlers.
The round dial gear train is designed so that you can swap the stud and box gears, and there is a lot of adjustment room for the idlers. The square dial gear train has a lot less lattitude for adjustment, so a transposing gear is necessary if you want metric threading. The basic question we wanted to answer was whether we could find a metric threading solution for the round dial that was based only on changing the stud and box gears, without a transposing setup.

I re-worked the perl program that was designed around the transposing gear setup used by the square dial, and will post the result separately.

The bottom line is that there is tremendous flexibility with the round dial gear train. The problem wasn't finding a good solution for metric threading, it was finding one that was as simple as possible, and used a relatively small number of gears. Many other equally good solutions are possible, so if you already have some 16dp gears in hand, run the perl program, or study its output, and you may have a solution with no out of pocket expense.

Here is the solution I am going to use on the 1940 10EE:

The gear train comes with 24 and 48 tooth gears already. I happened to have a 30 and a 38 tooth 16dp gear already, so they became part of the solution. To that, I just need to add a 51 tooth gear and a 37 tooth gear, and it will enable the following metric pitches, all with a pitch accuracy of .001 or less (0.1% or so). First a word of explanation: ratio means A,B or C on the gearbox dials, which give a 1.0, 2.0 and 4.0 ratio to the base tpi's. tpi is the thread dial setting on the "A" row.

You'll notice that none of the pitches larger than 2.5mm are possible using this system. To get them, a transposing gear would be required. I don't expect to have a need for those high pitches, any way.

matches for 0.25 +/- 0.001:
0.249019607843137 - box:24 stud:51 ratio: 2 tpi: 12
0.249019607843137 - box:30 stud:51 ratio: 2 tpi: 15
0.249019607843137 - box:48 stud:51 ratio: 4 tpi: 12
0.249884259259259 - box:51 stud:48 ratio: 4 tpi: 13.5
0.250657894736842 - box:24 stud:38 ratio: 2 tpi: 16
0.250657894736842 - box:30 stud:38 ratio: 2 tpi: 20
0.250657894736842 - box:48 stud:38 ratio: 4 tpi: 16
0.250831600831601 - box:38 stud:37 ratio: 4 tpi: 13
matches for 0.3 +/- 0.001:
0.299861111111111 - box:51 stud:30 ratio: 4 tpi: 18
matches for 0.35 +/- 0.001:
0.349627976190476 - box:37 stud:24 ratio: 4 tpi: 14
0.349627976190476 - box:37 stud:48 ratio: 2 tpi: 14
0.349710144927536 - box:38 stud:30 ratio: 2 tpi: 23
0.350472040668119 - box:38 stud:51 ratio: 2 tpi: 13.5
matches for 0.4 +/- 0.001:
0.399814814814815 - box:51 stud:30 ratio: 4 tpi: 13.5
0.400596760443308 - box:37 stud:51 ratio: 1 tpi: 23
matches for 0.45 +/- 0.001:
0.449791666666667 - box:51 stud:24 ratio: 4 tpi: 15
0.449791666666667 - box:51 stud:30 ratio: 4 tpi: 12
0.449791666666667 - box:51 stud:48 ratio: 2 tpi: 15
matches for 0.5 +/- 0.001:
0.499768518518519 - box:51 stud:24 ratio: 4 tpi: 13.5
0.499768518518519 - box:51 stud:48 ratio: 2 tpi: 13.5
matches for 0.6 +/- 0.001:
0.599722222222222 - box:51 stud:30 ratio: 2 tpi: 18
matches for 0.7 +/- 0.001:
0.699255952380952 - box:37 stud:24 ratio: 2 tpi: 14
0.699255952380952 - box:37 stud:48 ratio: 1 tpi: 14
0.699420289855072 - box:38 stud:30 ratio: 1 tpi: 23
0.700944081336238 - box:38 stud:51 ratio: 1 tpi: 13.5
matches for 0.75 +/- 0.001:
0.749652777777778 - box:51 stud:24 ratio: 2 tpi: 18
0.749652777777778 - box:51 stud:48 ratio: 1 tpi: 18
matches for 0.8 +/- 0.001:
0.79962962962963 - box:51 stud:30 ratio: 2 tpi: 13.5
matches for 0.9 +/- 0.001:
0.899583333333333 - box:51 stud:24 ratio: 2 tpi: 15
0.899583333333333 - box:51 stud:30 ratio: 2 tpi: 12
0.899583333333333 - box:51 stud:48 ratio: 1 tpi: 15
matches for 1 +/- 0.001:
0.999537037037037 - box:51 stud:24 ratio: 2 tpi: 13.5
0.999537037037037 - box:51 stud:48 ratio: 1 tpi: 13.5
matches for 1.2 +/- 0.001:
1.19944444444444 - box:51 stud:30 ratio: 1 tpi: 18
matches for 1.25 +/- 0.001:
1.2503861003861 - box:51 stud:37 ratio: 1 tpi: 14
matches for 1.5 +/- 0.001:
1.49930555555556 - box:51 stud:24 ratio: 1 tpi: 18
no matches for 1.75 +/- 0.001
matches for 2 +/- 0.001:
1.99907407407407 - box:51 stud:24 ratio: 1 tpi: 13.5
no matches for 2.5 +/- 0.001
no matches for 3 +/- 0.001
no matches for 3.5 +/- 0.001
no matches for 4 +/- 0.001
no matches for 4.5 +/- 0.001
no matches for 5 +/- 0.001
no matches for 5.5 +/- 0.001
no matches for 6 +/- 0.001

-Dave

2. Diamond
Join Date
May 2003
Location
Walla Walla Wine and Wild Turkey
Posts
4,180
Great Job!!!!

3. Stainless
Join Date
Oct 2003
Location
ohio
Posts
1,260
Yes.Thanks alot Dave I will see what I can scrounge up in gears and give it a try.

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