taken into considerations. This method is simple and inexpensive. However it needs different setting for every change in the number of teeth for a given pitch and accuracy is limited by the least count of instrument. Since the wear during use is concentred on the two jaws, the caliper has to be calibrated at regular intervals to maintain the accuracy of measurement. Where w- chordel thickness or width d- chordel addendum Directly the value of w can be found out the formula. w- Nm sin (90/N) Where N-total no of teeth of the given gear m- Module (which is given or determined) Once this value is known then directly we can find the value of chordel addendum with the help of gear tooth vernier caliper (by setting the value of w in the caliper). The formula to find out theoretical chordel addendum is D= Nm /2 {1+2/N-COS (90/N)} PROCIDURE: When two measuring tip surfaces are in contact with each other, check for zero error. Count the number of teeth on gear wheel. The chordel thickness or width of the gear is calculated by using the formula for w. module ‘m’ is to be obtained either by design specification or by trial and error. Bear in mind that module will be usually a whole integer 3 to 10 or at most 0.5 more than a whole number .To arrive at correct first approximately measure w at about the pitch circle and calculate using the ‘m’ ‘m’ formula for w .now round off the value for and recalculate with this new ‘m’ ‘w’ ‘m’. The value of chordel thickness is set on caliper (on horizontal beam) and chordel addendum is measured by using gear tooth vernier (on vertical beam). Thus the chordal addenda of several are measured and their average is taken as the actual value of the chordel addendum for the gear along with the for the variation of the average. σ If any error in the instrument is found then it is added to the obtained value accordingly. The measured value is compared with the calculated value . if the difference is within limits the chordel addendum is accepted . Where thickness correction has been indicated in the design this should be considered when calculating by using the actual value of ‘m’ ‘w’.
taken into considerations. This method is simple and inexpensive. However it needs different setting for every change in the number of teeth for a given pitch and accuracy is limited by the least count of instrument. Since the wear during use is concentred on the two jaws, the caliper has to be calibrated at regular intervals to maintain the accuracy of measurement. Where w- chordel thickness or width d- chordel addendum Directly the value of w can be found out the formula. w- Nm sin (90/N) Where N-total no of teeth of the given gear m- Module (which is given or determined) Once this value is known then directly we can find the value of chordel addendum with the help of gear tooth vernier caliper (by setting the value of w in the caliper). The formula to find out theoretical chordel addendum is D= Nm /2 {1+2/N-COS (90/N)} PROCIDURE: When two measuring tip surfaces are in contact with each other, check for zero error. Count the number of teeth on gear wheel. The chordel thickness or width of the gear is calculated by using the formula for w. module ‘m’ is to be obtained either by design specification or by trial and error. Bear in mind that module will be usually a whole integer 3 to 10 or at most 0.5 more than a whole number .To arrive at correct ‘m’ first approximately measure w at about the pitch circle and calculate ‘m’ using the formula for w .now round off the value for ‘m’ and recalculate ‘w’ with this new ‘m’. The value of chordel thickness is set on caliper (on horizontal beam) and chordel addendum is measured by using gear tooth vernier (on vertical beam). Thus the chordal addenda of several are measured and their average is taken as the actual value of the chordel addendum for the gear along with the σ for the variation of the average. If any error in the instrument is found then it is added to the obtained value accordingly. The measured value is compared with the calculated value . if the difference is within limits the chordel addendum is accepted . Where thickness correction has been indicated in the design this should be considered when calculating ‘m’ by using the actual value of ‘w’.
10263_290720161._USE_OF_GEAR_TOOTH_VERNIER_CALIPER_-_Copy.docx