<p style="text-align: center;"><img src="/ueditor/php/upload/image/20260320/1773969024159518.png" title="1773969024159518.png" alt="1.png"/></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 12px;">The wear of the pinion and gear will increase the backlash in a used unit. If the backlash in the new set is an amount of X, then before replacing a worn or damaged member, the backlash of the gearset should be measured on the outside of the ring gear as shown in Figure 1 (Ref. 1). If it is not possible to measure backlash due to the damage, then the backlash after replacing the damaged member should be adjusted to the maximum of the defined backlash range.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 12px;">Adjusting the backlash at the time of replacing one member reduces the risk of root interference due to the wear step (see Figure 2) and small flank form changes on the member that is not replaced.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 12px;">If there is a severe wear step between flanks and root fillet transitions on the member, which is not replaced, then the likelihood of an interference problem still exists. A severe wear step, as shown in Figure 2, can be detected visually or with a drawing pin.</span></p><p style="text-align: justify;"><span style="font-family: arial, helvetica, sans-serif; font-size: 12px;">To account for a severe wear step in the root of the undamaged member, the replacement gear must be topland chamfered to prevent interference between the topland corner of the replacement part and the wear step between the flank and root on the teeth of the new member. Topland chamfering is not a widely used standard practice for the case of single-member replacements. The consequence of not applying the service backlash and the topland chamfering is, in many cases, a repeated failure of the unit in question and a costly repeated repair. Topland chamfers, as shown on a pinion (top) and a gear (bottom) in Figure 3, should only have a width of 10 percent of the whole depth of the teeth and an angle that is about 30 degrees to the flank profile at the tip of the teeth. Curved tip roundings are even better than straight chamfers and are recommended if the provision of machining these is available. Rounded top-land corners have advantages over straight chamfers in the case of replacing damaged and worn gears.</span></p><p><br/></p>