Methods for determining the specifications of gears

Illustrated below are procedural steps to determine the specifications of a spur gear

Step 1. Count how many teeth a sample spur gear has  Z          

 

Step 2. Measure its tip diameter da                                                  

 

Step 3. Estimate an approximation of its module, assuming that it has an unshifted standard full depth tooth, using the equation:

 

Step 4: Measure the span measurement of k and the span number of teeth. Also, measure the k-1. Then calculate the difference.

Span number of teeth k=                                                                                           Span measurement Wk =   

Span number of teeth k-1 =                                                                                       Span measurement Wk-1 = 

                                                                                                                                                                                    The defference  = 

Step 5: This defference represents Pb = pm*cosa

Select module m and presure angle a from the table on the below (attachment table1)
                                                m =  
                                               
                                                a =    
 

Step 6: Calculate the profile shift coefficient x based on the above m and presure angle a and span measurement W.

                                               x =   

To find the calculation method, please see at the next topic!

Attachment table
Note:
 This table deals with the presure angle 20o and 14.5o only. There maybe cases where the degree of the presure angle is difference. Tooth profile come with deep tooth depth or shallow tooth depth, other than a full tooth depth.