Planetary milling machine

A milling cutter for cutting helical threads on a stationary worksurface, comprising in combination:

• a housing supporting a threaded lead nut transversely disposed relative to its longitudinal axis, a guide member axially disposed in threaded engagement with said lead nut and a hanger member pivotally connected to the guide member for free rotation about said axis and jointly longitudinally displaceable with the guide member therealong,
• first rotational means for turning the guide member relative to the lead nut,
• second rotational means for turning the hanger member independent of the connected guide member, whereby an offcenter point of the hanger member is movable in a helical path upon concurrent axial displacement,
• a generally radially disposed drive spindle extending from the hanger member and distally carrying a rotary milling cutter which is thus movable in a planetary path relative to said longitudinal axis, and
• drive coupling means adapted to operate each of said rotational means concurrently at speeds adapted to produce a selected pitch of the helical path and of the resultant thread cut therealong.

In combination with a planetary milling machine such as adapted to overlie a work surface within the bore of a fixed workpiece and having means for selective extension of a support structure carrying a generally radially directed cutter movable toward and away from functional cutter-engagement with such bore, the improvement wherein

• said extension means comprise a support for said cutter, guide means for selectively moving the support in a direction transverse to said bore, walls forming a longitudinal channel extending along an edge of said support in said transverse direction, a threaded nut and a positioning screw threadedly traversing said nut, both of which are located in said channel, one secured to said support and the other secured to said milling machine, whereby selective rotation of said screw effects transverse movement of said support and cutter,
• remote operating means for jointly retracting and extending the threaded nut and positioning screw lengthwise along said channel, whereby the support and cutter may be moved jointly toward and away from said worksurface, and
• remote operable brake means for anchoring said support at a selected radial position corresponding to desired work-location of the threaded nut, whereby the support and cutter may be preset for a required bore-contacting position when separated from the workpiece and then be retracted from the preset position for axial insertion and withdrawal of the milling machine from the mouth of the bore, and alternately extended to work-contact position after being placed within the bore.

A guidance and operating assembly for imparting correlated axial and rotational movement to a carried support structure which is displaceable along a longutudinal axis of the assembly, whereby an offcenter point of such structure may be moved in a helical path of selected pitch, said assembly comprising in combination:

• a tubular housing supporting a threaded lead nut transversely disposed along the longitudinal axis thereof,
• first and second tubular sleeves spaced from each other and from said lead nut along said axis, each sleeve being disposed for independent rotation in a respective annular guideway of said housing,
• a guide member disposed in threaded engagement with said lead nut and having spline means which dispose it in longitudinal sliding engagement with said first sleeve, whereby the guide member may be driven by rotation of the first sleeve and simultaneously moved axially by its engagement with the lead nut,
• a hanger member distally carrying a longitudinally disposed support structure and having spline means in longitudinally displaceable engagement with said second sleeve, whereby the hanger member is simultaneously rotatable in unison with and by rotation of the second sleeve, the hanger member being attached proximately to said guide member by axial pivot means preventing its longitudinal separation therefrom, whereby the rotatable hanger member is also moved longitudinally by axial movement of the guide member,
• and drive means adapted to rotate each of said tubular sleeves concurrently at selected speeds and thus apply their resultant velocity ratio to the hanger member so as to move said offcenter point of the carried support structure in a helical path having a pitch dependent upon said ratio.