These clamping screws are used with PTPD block pull clamps. Block pull clamps provide very quick and secure fastening and are ideal for 5-axis machining. They consist of a clamp base used with these clamping screws. Block pull clamps mount under a workpiece, which allows the surface that will be machined to be fully open for the cutting tool. In addition to tightening with a wrench, this clamp can be operated with nut runner for automation and impact wrench for lower workload. Made from 4135 steel, quenched and tempered, with a black oxide finish.