Calculating the dimensions of a straight stub-toothing

The characteristic of a stub-toothing is a reduced tooth height till approximately ¾ of the normal tooth height. By this smaller height the tooth possesses a wider basis and the moment of bending as result of the tooth force becomes also smaller. This results in a greater resistance to tooth breakage.

Together with a slight reduction in dimensions these are the only advantages of a stub-toothing. On the other hand, the length of the contact line is greatly reduced through which the unreeling of the two gears on each other runs less smoothly with an increased risk of sound levels.

The use of stub-toothing belongs more to the past; nowadays it is more limited to gears intended for the transmission of a large torque, but only for occasional use. The production of a stub-toothing requires special tools.

The characteristics of a stub-toothing are indicated by a combination of digits for the tooth depth and module. For example: 6/4 describes a gear with module 6 with tooth depths that belong to a module of 4.

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Generally, a stub-toothing in the English system is being applied as for example: 8/DP10 10DP which means that the module = 25.4/8 = 3,175 with a tooth depth of DP10 = 25.4/10 = 2.54. The dedendum is usually 1.25 x module and the pressure angle 20 degrees.

For measuring of the tooth thickness the Wildhaber measurment can be used as is the case for standard gears.

Further dimensions are listed in the following table:

Module of the pitch = m = Image155Image156 or Image8
Module for the tooth depth = m’ = +/-75 x m (according the systems)
Number of teeth = z = Image111 or Image159
Pitch diameter in mm = d = z.m or Image160
Tip diameter in mm = da = d + 2.m’
Facewidth in mm = b = 10.m (normal)
Tooth depth in mm = h = 2,25.m’
Addendum in mm = ha = m’
Dedendum in mm = hf = 1,25.m’
Rim thickness under the tooth in mm = H = approx 1,5 x m’
Centre distance = a = Image144Image161