webbed material to provide the necessary camming action with balanced stress across its width or it may be used in tandem to eliminate mobius twist of the material such a bi helical plane surface can be produced by casting forming machining or by extrusion a bi helical plane surface can be machined using a programable machine center or by using special machine attachments such attachments must make it possible to rotate and translate the material relative to the cutter or vice versa at such a rate as would define the camming angle in addition the cutter axis must be capable of adjustment to an angle equivalent to the helix angle or its complement relative to the material axis of rotation it has been determined that standard production equipment is not well suited for manufacture of a bi helical plane but a rotating table can be installed on a milling machine to generate such a camming plane since a mills axis are perpendicular a camming plane parallel to the helical axes will be produced additional modification of the millhead angle will then be required to manufacture the bi helical surface a standard lathe generates a helix at right angles to the axis of rotation when.