Posted by gearhead1 on April 03, 2013 at 13:25:22:
In Reply to: Re: Hobbing Prime Spurs using differential posted by Bill Simpson on March 29, 2013 at 12:23:46:
Example -
From that page's directions -
C = Pi/(NDP * Feed desired * sine of Helix Angle)
C = 3.1416 / (16.933333 * .019685" * sine of 15.625°)
C = 3.1416 / (16.933333 * .019685 * .26934)
C = 34.99262
K ( machine index costant) * C * hob threads
7.5 * 34.99262 * 1 = 262.44465
C * N - 1
34.99262 * 71 teeth - 1 = 2483.47602
From above - 262.44465 / 2483.47602 = .105698881
This should be the new index gears that will make a 15.625° RH Helix 71T gear of 1.5Mod ( 16.93333 DP )
Then, the new feed gears are calculated -
Feed desired / Machine's feed constant
.019685" / .8 = .02460625" ( happens to be .625mm )
So, I put those new index gears in, the new feed gears in, and the gears tha make a 15.625° LEFT hand helical gear in teh differential, and I get ... ... ...
NOT a spur gear.
I get something tat looks like a 1° LH helical...
WTF, over.