The effect of tooth geometry on power hacksaw blade performance.

Published work concerning the influence of tooth geometry on hacksaw blade performance has been reviewed. By testing standard and modified hacksaw blades the author has shown that, contrary to previous belief, pitch is not a parameter which affects blade performance. Furthermore experimental evidence is presented to show that gullet size and shape significantly affect blade performance. The author proposes that restriction of chip flow by the gullet causes very inefficient metal removal. This is supported by examination of hacksaw chips, and a theoretical model has been developed to show how rapidly cutting forces increase when the chip is restricted from flowing. Two testing procedures have been developed to examine chip formation in the gullet. The first procedure employs video equipment to show chip formation and cutting forces simultaneously on one VDU, during cutting with single hacksaw teeth. This test is of limited use due to the slow cutting speeds employed. The second procedure, also using single teeth but cutting at realistic speeds, was capable of testing any tooth/gullet geometry cutting any material. The test results confirmed that restriction of chip flow by the gullet produces inefficient cutting. It has been shown that a particular tooth/gullet geometry can only cut efficiently over a limited range of feeds and workpiece lengths. The author has developed a method for accurately predicting sawing rates from the single tooth data gathered. The information gathered from the single tooth tests has enabled the author to isolate the most important aspects of tooth geometry affecting blade performance, and as a result, a new tooth design has been developed which performs better than the standard tooth.