Machinist's clamp

Clamp apparatus comprising a step clamp having a forward end for holding a workpiece and a rear end having means for affixing said step clamp to a forward vertical face of a step block, and separate means for longitudinally and vertically adjusting said forward end of said step clamp to provide for securing and releasing said workpiece to and from a work surface, wherein said means for affixing said step clamp to said step block comprises a generally "U"-shaped holder assembly having a "U"-bend, said holder assembly affixed to the rear end of said step clamp which enables said holder and step clamp to be removeably attachable to said step block, said holder having thumbscrew means threadingly inserted through the "U"-bend, said thumbscrew means having a thumb adjustment external to the "U"-bend and having a resilient endpiece affixed internal to the "U"-bend adjacent a rear vertical face of said step block, whereby, when said step clamp is adjusted to a desired height on said step block and said thumbscrew assembly is advanced such that said resilient endpiece thereof is forced into tight holding contact with the rear vertical face of said step block and said rear end of said step clamp is affixed to said forward vertical face of said step block, and whereby a rigid combination of step clamp, step block and holder is provided, such that, when a workpiece is removed from said apparatus, the step clamp does not fall away from the step block, thereby avoiding unnecessary time delays in re-setup.