to the description of the standoff elements 2 and 3 above the flow channels defined by the grooves 22 and 32 respectively are also open at both ends in the preferred embodiment because the standoff elements are capable of withstanding the relatively high impact loads that result from contact with the wellbore wall they are able to keep the agitator 1 which is of a smaller outer diameter than that of the standoff elements 2 and 3 from having any contact with the wall of the wellbore because of this separation of duties the agitator 1 design and construction have no need for the same level of strength and durability that the standoff elements 2 and 3 must have freed of the burden of having to withstand high loads the design of the agitator 1 can be surgically suited to its sole purpose which is to mobilize the cuttings that build up on the low side of the wellbore so that the cuttings can be swept into the flowstream of the mud and carried up to the surface leaving behind a cleaner wellbore that presents less drag on the drill string specifically the blades 11 of the agitator 1 as compared to the blades of the standoff elements 2 and 3 have a sharper pitch in the curvature of the blade are more densely arranged and thus there are more of them and have a more aggressive profile described below the pitch of the helical curves of the blades 11 is essentially the ratio of the circumferential displacement of the blade relative to the axial displacement of the blade across a given axial length of the agitator 1 just as pitch is defined for.