Bar Clamp with Die-Formed Notches: Hargrave, 1927

A cabinetmaker's bar clamp has a screw-adjusted jaw at one end of a bar and a sliding jaw held by a pawl in teeth along the bar. Teeth cut into the bar's edge weaken it, cannot be spaced closely, and wear until the pawl slips. John M. Hargrave of Cincinnati patented the fix in 1927, US 1,638,848: use an I-section bar and press a row of depressions into the side of its web with dies. Each depression has an abrupt, deep shoulder for the pawl and a sloping face away from it. Nothing is cut away, the corrugations stiffen the bar, the notches can be close together, and pressing them is cheaper than cutting.