Ingersoll Rand revamps die grinder series Ingersoll Rand now delivers the world's first professional cordless die grinders with the release of the Series GS25 and GR25 die grinders. The 14.4-volt, 0.35 horsepower die grinders come in both straight and right angle configurations, each producing a maximum free speed of 27,500 rpm and 20,000 rpm respectively. A dual ball bearing design increases tool reliability, ensuring longer runtimes for increased productivity.