SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING Metal removal rates are high since no reciprocation of hob or workpiece is required and so cutting speeds of 40 m/min can be used for conventional hobs and up to 150 m/ min for carbide hobs. Typically with a100 carbide硬质合金 mm diameter hob the rotation speed will be 100 pm and so a twenty tooth workpiece roughing粗加工 will rotate at 5 rpm. Each revolution of the workpiece will correspond to0.75 mm feedcoarse大的,粗的 so the hob will advance through the workpiece at about 4 mm per minute. For car production roughing multiple start hobs can be used with coarse feeds of 3 mm per revolution so that 100 rpm on the cutter,a two-Start hob and a 20 tooth gear will give a feed rate of 30mm/minuteSCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING Metal removal rates are high since no reciprocation of hob or workpiece is required and so cutting speeds 0f 40 m/min can be used for conventional hobs and up to 150 m/min for carbide hobs. Typically with a 100 mm diameter hob the rotation speed will be 100 rpm and so a twenty tooth workpiece will rotate at 5 rpm. Each revolution of the workpiece will correspond to 0.75 mm feed so the hob will advance through the workpiece at about 4 mm per minute. For car production roughing multiple start hobs can be used with coarse feeds of 3 mm per revolution so that 100 rpm on the cutter, a two-start hob and a 20 tooth gear will give a feed rate of 30mm/minute. carbide 硬质合金 roughing 粗加工 coarse 大的，粗的