Bosch 1-9/16 In. Spline Combination Rotary Hammer. The new spline combination rotary hammer from Bosch provides maximum productivity in all day drilling and chiseling applications. Equipped with 6.1 ft/lbs of impact energy (E.P.T.A.). The new RH540S provides up to 39% more impact energy versus the previous model for best in class performance. The new RH540S also provides variable speed. This delivers better bit control during application start-up.