in a range of about 0 u00b0 to about 70 u00b0 when a radial load l is applied to outside roller 1602 it is believed that protrusion 1612 applies a radial load r and an axial load a to pipe end 1616 the axial load tends to push the pipe material toward protrusion 1610 this action produces a higher groove edge wall 1614 than typical with a conventional outside roller e g an outside roller without a protrusion 1612 groove edge wall 1614 is formed with a substantially vertical face 225 which intersects an adjacent arcuate portion 1630 having a tangent at an intersection angle d to the vertical face 1625 it is believed that protrusion 1612 with chamfered surface 1613 tends to minimize intersection angle d which helps to minimize shearing of the groove wall a small intersection angle d provides a steeper groove edge wall 1614 this is advantageous because it improves the attachment of the pipe to the coupling increasing the pressure rating of the joint and the ability of the joint to resist bending the radial load r applied to pipe 1608 by protrusion 1612 also acts to resist flaring of pipe end 1616 tending to keep pipe end 1616.