In the case of clamping products, a clear distinction must be made between exerting forces and holding capacities. Here are the essential features.
Manually operated clamps present a series of variables to determine actual exerting force. These variables are:
The “holding capacity” of Destaco toggle clamps has been determined by actual tests. It is defined as the maximum amount of force which may be applied to the work holding bar, in the closed position, without creating permanent deformation of the clamp components. This maximum force is measured at a point closest to the base and diminishes as the spindle approaches the end of the bar. The ratings for holding capacity are maximum and should not be exceeded. These values include a safety factor.
The table below depicts holding capacity (HC) and clamping force (EF) data for a typical manual clamp. The clamping force (EF) is expressed as a ratio of the force that is applied to the clamp handle (AF). In this example, either 10:1 or 5.3:1 depending upon position of the clamping point on the clamp arm. That is, at position X1, the maximum clamping force (EF) that can be generated is 10 times the force that is applied to the clamp handle.
AF = 90 ÷ 10 = 9N [40lbf.]
EF = 5 · 5,3 = 26,5N [120lbf.]
The holding capacity (HC) ratings shown in the table are in relation to the pivot point of the clamping arm. This is useful in estimating the holding capacity at an intermediate clamping point along the arm, or at a point beyond the length of the standard clamping arm.
Xc = 40mm + X = 40mm + 40,5mm = 80.5mm
M = X1 HC1 = 49,5mm x 4450N = 220275 N mm
HC = M ÷ Xc = 220275 ÷ 80,5 = 2736N [615lbf.]
Xc = 25+X2 = 25 + 99,5 = 124,5mm
M = X2 HC2 = 99,5mm 2090mm = 207955 N mm
HC = M ÷ Xc = 207955 ÷ 124,5 = 1670N [375lbf.]