Rotary machining tool and method of its manufacture

A method of manufacturing a rotary machining tool which comprises:

• a. placing pin receiving apertures in a generally disk-shaped tool body at a plurality of spaced apart locations around a circle concentrically located adjacent to and lying within the peripheral edge of the tool body;
• b. forming a plurality of cutter element retaining sockets around the tool body peripheral edge by pinning an inverted generally U-shaped clevis means to the periphery of the tool body at each aperture, each clevis means having a basal portion extending outwardly from the tool body periphery to define a generally tangential tapered cutter element retaining socket between the clevis upper portion and the tool body peripheral edge;
• c. buttressing the clevis means against the tool body to ensure against rearward rotation of the clevis means when the tool is subjected to operating stresses;
• d. providing replaceable cutter element means having head and elongated tapered shank portions;
• and
• e. wedging the tapered shank portion of a cutter element means into each cutter element retaining socket thereby forcing the clevis means radially outward against the attaching pin to tightly lock the assembly until the cutter element means is driven out for sharpening or replacement.

An insertible cutter element for a rotary machining tool which comprises:

• a head portion having at least one cutting edge;
• and
• a shank portion extending rearwardly from the head portion for insertion into a retaining means on a rotary machining tool, said shank portion having lower, side and upper surfaces,
• said lower surface being essentially planar in configuration,
• said upper surface being sufficiently rearwardly tapered with respect to the lower surface, when seen in side profile, to form a self-releasing taper, and
• said side surfaces being rearwardly tapered in reference to each other, as seen in top profile, to form a self-locking taper.

A clevis for attaching a removable cutter element to a generally circular tool body, said cutter element being of the type having a head with at least one cutting edge and a shank extending rearwardly from the head and said tool body having spaced peripheral notches or gullets and marginally adjacent apertures for attachment of the clevis, which comprises:

• a. two mirror image side portions spaced apart for snugly stradding the circumferential edge of the tool body, said side portions having upper and lower ends and leading and trailing edges, both side portions being transversely apertured along a common axis for receiving a pin for attachment to the tool body;
• b. a transverse upper member bridging the upper ends of the side portions to form a structure of inverted, generally U-shaped transverse cross section,
• said upper member having an inside surface with a longitudinal centerline forming an angle with the projected leading edges of the side portions falling between about 70.degree.-90.degree.,
• said upper member and the upper part of the side portions forming three sides of a socket defining upper portion of the clevis for retaining the shank of the cutter element;
• and
• c. a reinforcing buttress strap bridging in part the leading edges of the side portions, the upper ends of the side portions remaining unbridged to form the entrance of the cutter element retaining socket,
• the edges of the buttress strap adjoining the side portions being chamfered so as to create an outside face portion on the buttress strap that does not exceed in width the spacing between the side portions,
• the apertures in the side portions being located so that the socket defining upper portion of the clevis will extend beyond the periphery of the tool body when the clevis is installed and the circumferential edge of the tool body will form a fourth side of the retaining socket for receiving the shank of a cutter element, and said buttress strap will bear against the gullet or notch in the periphery of the tool body to resist rearward rotation during use of the tool.