Abstract: An elongated pump rod or sinkerbar for use in a pump rod string for a downhole reciprocating well pump is provided with an elongated sleeve of high density or ultra high density polyethylene over a major portion of the length of the sinkerbar to minimize wear on the sinkerbar and a well tubing string as a consequence of deflection of the sinkerbar into engagement width the tubing string and to minimize frictional drag on the pump actuating mechanism as a result of such engagement. The polyethylene sleeve may be assembled over the sinkerbar by apparatus including an elongated hydraulic actuator which may be configured to push a sinkerbar into the sleeve while the sleeve is held stationary within a support tube, or by holding the sinkerbar stationary on a support and pulling the sleeve over the sinkerbar and from a continuous length of tubing from which the sleeve is formed.

Abstract: A new and improved sinker bar has a substantial portion of its body square in cross section which increases rigidity and decreases wall to wall contact downhole in the production of fluids utilizing a sucker rod string. In addition, when the bars are used with a certain percentage of sucker rods, a greater efficiency and thus reduction of friction is accomplished in production of the fluids downhole.