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+--- Thread: L.S. Harrison & sons Ltd, 11" (/thread-2791.html)
RE: L.S. Harrison & sons Ltd, 11" - f350ca - 08-13-2015
Hi Michael
Still a little early of me but think these numbers are correct. Check with a thread gauge please.
For the bottom four rows on your chart the change gears are a 25 and a 100 (the middle gear doesn't matter) or 4:1 reduction
If you go with the 25 and 127 tooth gears you'll get 5.08:1 reduction
Or a change in reduction of 5.08/4 or 1.27 lower than the chart.
For an easy set of numbers 10 tpi would be 2.54 pitch (2.54 mm/rev) with the 127 tooth gear we reduce the movement by 1.27:1 so 2.54/1.27 gives 2 mm/rev.
The same ratios apply to all the threads soup get the bottom chart
TPI 15 14 13 12 11 10 9.5 9 8
Pitch 1.33 1.43 1.53 1.66 1.81 2 2.11 2.22 2.5
TPI 30 28 26 24 22 20 19 18 16
Pitch .666 .714 .769 .833 .909 1 1.05 1.11 1.25
TPI 60 56 52 48 44 40 38 36 32
Pitch .333 .357 .384 .416 .454 .5 .526 .555 .625
TPI 120 104 104 96 88 80 76 72 64
Pitch .166 .178 .192 .208 .227 ,25 .263 .278 .313
For the top row with the 50 and 127 tooth gears the ratios change the same so
TPI 7.5 7 6.5 6 5.5 5 4.75 5.5 4
Pitch 2.66 2.86 3.06 3.32 3.62 4 4.22 4.44 5
Hopefully no typo's there.
For some threads you'll have to approximate, .75 pitch you'd have to live with .769 for a 2 1/2 percent error
Hope this helps.
RE: L.S. Harrison & sons Ltd, 11" - Steinmann - 08-14-2015
Thank you all very very much.
I'll check all this info.
Have a nice week end.