as an abutment against which shoulder 28 of the insert is placed to accurately position the insert in the groove and provide repeatability of accurately positioning replacement inserts the insert is held in position in one of the grooves 72 by means of a clamp 74 which is secured to end portion 68 by means of a fastener such as a machine screw 76 passing through an aperture 78 in clamp 74 and into a threaded hole 80 formed in end portion 68 clamp 74 as it is tightened against planar surface 70 and end portion 68 by machine screw 74 causes the insert to self orient by rotating its body 12 to cause the substantially planar portion 18 to align horizontally with the bottom surface of the clamp inserts 10 40 50 secured in toolholder 60 are particularly useful for grooving and turning of a workpiece the body of toolholder 90 is similarly configured as compared to body 62 of toolholder 60 and the same reference numbers and description as for holder 60 and in fig1 and 13 are utilized for identical configuration elements for toolholder 90 and in fig2 and 14 toolholder 90 differs from toolholder 60 in the configuration of its distal end portion 92 end portion 92 also has a planar surface 94 but a single insert receiving groove 96 is provided transversely to the axis of body 62 adjacent the distal end 98 of end portion 92 further as shown in fig1 two threaded.