DIY Knowledge

Spline shanks


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For a positive interlocking connection between the drill chuck and the drill bit shank, medium and large rotary hammers require a large-surface tool fitting. Hexagonal shanks were in use for a number of years, but they tended to wear out rather quickly. The spline shank drive developed by BOSCH lasts considerably longer.

The ends of large spline shanks have straight grooves whereas small spline shanks have twisted grooves. The spline shank profile provides a much larger surface for power transmission than conventional shanks which leads to a considerable increase of both efficiency ratio and service life. Medium-weight rotary hammers use the small spline shank, heavy-duty rotary hammers of more than 6 kg use the large spline shank. SDS-max is the result of the advanced development of the large spline shank.