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Cutting a rack

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Baz	15/03/2017 11:45:36
1033 forum posts 2 photos	I need to cut a rack a couple of inches long. Can somebody please tell me how I calculate the pitch of the teeth? I have searched through all my books but they all seem to deal with cutting gears, no mention of racks.
Andrew Johnston	15/03/2017 12:19:22
7061 forum posts 719 photos	I assume that the rack is to mate with an existing gear. The tooth pitch of the rack will be the same as the circular pitch of the mating gear. In fact the tooth pitch of the rack is the circular pitch, just that the radius of the circle is infinite. For gears specified in DP the circular pitch (CP) is: CP = pi/DP As an example let's assume the rack needs to mesh with a 10DP gear. The circular pitch will be approximately: 3.14159/10 = 0.314159" If the DP is integer then the CP has to be irrational, which is a pain when 'indexing'. It would be best to calculate each value separately to avoid cumulative errors. Andrew
Baz	15/03/2017 12:47:19
1033 forum posts 2 photos	Andrew, yes it is to mate with an existing gear, thanks very much for the info. Barry

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