Method and apparatus for forming intermittent chips while machining holes with a rotating tool

A method for generating intermittent chips when machining a hole in a stationary workpiece on a machine with a rotating tool having one or more cutting edges, comprising the steps of:

• (I) rotating the tool about an axis of rotation coinciding with the centerline of a machined surface to be produced;
• (II) causing the tool to achieve strictly determined and controlled positions along its feed advance path in response to the tool angular positions when cutting, so that
• (a) a tool nose path described on the machined surface of the workpiece is wavy and has a constant wave amplitude A and wave length .lambda., said wave amplitude A and wave length .lambda. being capable of adjustment,
• (b) a distance p between neutral lines of any two consecutive tool nose path coils, produced by a given tool nose, is constant but adjustable, said distance p being capable of adjustment, and
• (c) a phase .phi. is produced between waves of any two consecutive tool nose path coils produced by a given tool nose, that is equal to 2.pi.[N-I(N)], where N is a selected number of waves of said wavy tool nose path per circumference of the machine surface of said hole and I(N) is the integer part of said N;
• (III) controlling said wave amplitude A according to the inequality ##EQU3## where p is said constant distance, N is said selected number of waves, and n is the number of major cutting edges in the tool, whereby the undeformed chip thickness varies periodically and reduces to zero in each period of its variation, thereby generating intermittent chips, or causing in some materials chip breakage when said amplitude is slightly less than that resulting from said inequality;
• and
• (IV) adjusting said amplitude A and said phase .phi. in any combination to achieve a desired surface finish and tool life.