frame 15 and housing 17 slot 26 is not more than a few inches wide however because frame 15 does not move far with respect to housing 17 before coming to equilibrium again due to the tightening of the vise described below as frame 15 moves in a clockwise manner the end of first yoke arm 18 moves upwardly in frictional sliding contact with the slightly convex exterior surface 23 of the wedge shaped flange 21 of first vise jaw 14 as hydraulic cylinder 20 maintains upward pressure on yoke 16 and yoke arms 18 the slight clockwise rotation of frame 15 causes wedge shaped flange 21 of first vise jaw 14 to rotate downwardly with respect to the end of first yoke arm 18 the increasing thickness of metal between pipe 10 and the end of first yoke arm 18 caused by the outward flaring of wedge shaped flange 21 of first vise jaw 14 causes a greater wedging force to be exerted on pipe 10 than was exerted on pipe 10 before frame 15 rotated in response to the rotational force transmitted to it from pipe 10 because yoke 16 transmits the force exerted by hydraulic cylinder 20 to the remaining yoke arm 18 denoted second yoke arm as well as to the first yoke arm 18 second yoke arm 18 also experiences an upward force.