- Thread starter rrocky
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Not sure why but they work in real life. Could maybe be an error in tooth count?

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I can take a peek at it when I get home from work

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The OD of a gear is equal to (N+2) / DP and the Pitch diameter is equal to N X the DP, where N is the number of teeth and DP is the diametrical pitch.

Thus for the 48 tooth gear the OD is ((48+2) / 48) which is where the 1.0417 dimension comes from. But the Pitch diameter is equal to (48 /48) or 1.0000. Same thing applies to the 24 tooth gear which equals a Pitch diameter of 0.5000.

Thus the ratios of the pitch diameters is the 2:1 that you were expecting.