b'To enhance micromachining capabilities, low-speed machines can use spindle speeders.By Larry Adams machine. For example, in addition to pro-ducing and selling its line of VRT spindle M icroscale parts and features pres- speeders, Bryan Machine Service operates ent many challenges when ma- a machine shop. Sitting amid a variety of chining, not least of which are thehigher-tech equipment are two 50-taper, high spindle speeds required to reach ac- 7,000-rpm machines. One job required ceptable cutting speeds and cut rathermachining runners on a large plate, as well than rub workpieces or break tools. A lotas microfeatures.of shops have robust, accurate equipmentWith the spindle speeder, Bryan said,that has served them well through thewe can put on a18 "- (3.18 mm) or a116 "-dia. years but lacks adequate spindle speed. (1.59 mm) tool on that great big machine Many machines are built for torque,and run it at 30,000 rpm.not speed. A solution might be a special-ized micromachine or a premium machineNeed for Speedwith a high-speed spindle, but a spindleFaster spindle speeds can help impart speeder is another option. fine surface finishes and reduce burrs, Spindle speeders amplify speeds forchatter marks and other cosmetic blem-many jobs that need small-diameter tools,ishes. Carbide cutting tools also require often less than 6 mm (0.24"). Speeders mul- higher spindle speeds for best results.tiply spindle speeds by several times whileThe trick is to run at the right surface feet maintaining the torque of a machine. per minute, which also can be expressed The biggest problem with (using) smallin surface meters per minute. Essentially, tools is that the shop cant run them fastthe faster a spindle turns or the larger the enough, said Steve Bryan, owner of Bryandiameter of a tool is, the higher thesfm is Machine Service Inc., Huntington, Indiana.based on the formula in which sfm equals Spindle speeders can take an older ma- (rpm times tool diameter) divided by 3.82. chine and increase that up to 15,000 toFor instance, a 0.5"-dia. (12.7 mm) endmill 40,000 rpm. The older machines have arunning at 1,146 rpm achieves a cutting new life. speed of 150 sfm (45.72 m/min.) while a Spindle speeders are suitable for myriad0.05" (1.27 mm) tool must run at 11,459 rpm shank types, including small tapers that areto cut at 150 sfm, and a 0.005" (0.127 mm) lightweight and precisely produced for bal- tool needs an 114,592-rpm spindle speed ance and reduced total indicator runout. to reach 150 sfm.Because higher-end spindle speedersBut those numbers are just the start. Dif-are compatible with automatic tool chang- ferent materials cut best at specific speeds, ers, it is easy to do multiple setups on oneand each tool supplier suggests cutting The MO spindle speeder for micromachining applications can increase spindle speeds to 35,000 rpm.44MAY 2020 Micromachining.indd 44 4/16/20 6:03 PM'