HDG18-9RS. 1/4" Die Grinder .9 HP 18,000 RPM Rear Exhaust Safety Lever. Our Best Performing Die Grinders! High-power, lightweight and efficient tool designed for use in high-production applications. Great for grinding, deburring and polishing. Elite Series. HDG22-6FS. 1/4" Die Grinder .6 HP 22,000 RPM Front Exhaust Safety Lever.