Broaching apparatus and methods

A slot-completing broaching insert for performing a cutting operation with respect to sides of a roughed-out slot in a workpiece, comprising:

• a base portion adapted to be mounted in a tool holder, and
• a cutter portion projecting from said base portion in a direction transversely relative to a forward direction of cutting, said cutter portion including:
• a chip face facing in the forward direction of cutting, said chip face being bordered by an end edge and a pair of side cutting edges, said side cutting edges extending from said end edge toward said base portion along opposite sides of said chip face and being spaced from a center plane of said insert which passes through said base portion and said chip face, each of said side cutting edges including a scalloped region defined by a portion of said side cutting edge disposed forwardly relative to immediately adjacent portions thereof, in order to minimize the shock when said cutting edge engages a workpiece.

A broaching method for forming a slot in a workpiece comprising the steps of effecting relative linear movement between said workpiece and a broaching insert in a direction of cutting, with a face of said workpiece oriented obliquely relative to said direction of cutting, such that a pair of side cutting edges of said broaching insert contact said workpiece simultaneously, said broaching insert comprising a slot completing insert which widens and shapes a previously formed slot in said workpiece, said side cutting edges being scalloped whereby at least one portion of each said side cutting edge engages said workpiece face in advance of immediately adjacent portions of said cutting edge in order to minimize shock.

A broaching method for cutting a slot in a workpiece, comprising the steps of effecting relative linear movement between said workpiece and a slotter type of broaching insert in a direction of cutting to cause a cutting edge of said slotter insert to engage a face of said workpiece such that a center portion of said cutting edge contacts said workpeice ahead of opposing side portions of said cutting edge.

A method of broaching wherein a broaching insert is passed linearly through a workpiece from a front face to a rear face thereof to form a slot extending completely through said workpiece, the method including the step of gradually releasing a compressive load on said insert when said insert exits said workpiece by passing said insert sequentially through a plurality of back-up disks disposed at said rear face of said workpiece, said back-up disks being of less hardness than said workpiece and of sequentially reduced hardness relative to each other, whereby the compressive loading on said insert upon exiting said workpiece is gradually relieved as said insert sequentially passes through said back-up disks.

A slot-completing broaching insert for performing a cutting operation with respect to sides of a roughed-out slot in a workpiece, comprising;

• a base portion adapted to be mounted in a tool holder, and
• a cutter portion projecting from said base portion in a direction transversely relative to a forward direction of cutting, said cutter portion including a chip face facing in the forward direction of cutting, said chip face being bordered by an end edge and a pair of side cutting edges, said side cutting edges extending from said end edge toward said base portion along opposite sides of said chip face and being spaced from a center plane of said insert which passes through said base portion and said chip face, one of said side cutting edges disposed forwardly relative to the other of said side cutting edges, said chip face being divided in half by a forwardly projecting center flange lying in said center plane.

A slot-completing broaching insert for performing a cutting operation with respect to sides of a roughed-out slot in a workpiece, comprising:

• a base portion adapted to be mounted in a tool holder, and
• a cutter portion projecting from said base portion in a direction transversely relative to a forward direction of cutting, said cutter portion including a chip face facing in the forward direction of cutting, said chip face being bordered by an end edge and a pair of side cutting edges, said side cutting edges extending from said end edge toward said base portion along opposite sides of said chip face and being spaced from a center plane of said insert which passes through said base portion and said chip face, one of said side cutting edges disposed forwardly relative to the other of said side cutting edges, said side cutting edges defining a generally fir-tree shape.