Two-stage broaching of engine block bearings

A plural stage method of broaching a series of axially aligned bores, said method comprising in a first stage:

• providing a first elongated broach having a plurality of axially spaced, circumferentially extending cutting teeth and a plurality of arcuately spaced, longitudinally extending grooves which cross the cutting teeth and divide the cutting teeth into arcuate segments,
• providing a plurality of broach guides each having a plurality of ribs arranged in the same arcuately spaced relation as said grooves about an axis coinciding with the aligned axes of the bores,
• advancing said first broach through said bores and said guides with said ribs slidably received in said grooves to guide said broach and said cutting teeth segments broaching arcuately spaced sectors of said bores but leaving unbroached ridges therebetween,
• said method further comprising in a second stage:
• providing a second elongated broach having a plurality of axially spaced cutting teeth,
• and advancing said second broach through said bores to broach the ridges left in said first stage.

Apparatus for broaching a series of axially aligned and spaced bores comprising:

• a first elongated broach for broaching in an initial operation, said first broach having a plurality of axially spaced, circumferentially extending cutting teeth and a plurality of arcuately spaced, longitudinally extending grooves which cross the cutting teeth and divide the cutting teeth into arcuate segments,
• guide means for said first broach, said guide means comprising a plurality of guides, each guide having a plurality of ribs arranged in the same arcuately spaced relation as said grooves about an axis coinciding with the aligned axes of said bores,
• means for advancing said first broach through said bores with said ribs slidably received in said grooves to guide said first broach and said cutting segments broaching arcuately spaced sectors of said bores but leaving unbroached ridges therebetween,
• a second elongated broach for broaching in a subsequent operation,
• and means for advancing said second broach through said bores to broach the ridges left by the first broach.

A plural stage method of broaching a series of axially aligned bores, said method comprising in a first stage:

• providing a first elongated broach having a plurality of axially spaced, circumferentially extending cutting teeth, each cutting tooth being divided into arcuate segments with spaces between said segments, the arcuate segments of each cutting tooth being longitudinally aligned with the arcuate segments of the other cutting teeth,
• advancing said first broach through said bores and with said cutting teeth segments broaching arcuately spaced sectors of said bores but leaving unbroached ridges therebetween,
• said method further comprising in a second stage:
• providing a second elongated broach having a plurality of axially spaced cutting teeth,
• and advancing said second broach through said bores to broach the ridges left on said first stage, said second broach being provided with pilot means to guide on the arcuately spaced sectors of said bores which were broached in the first broaching stage.

A plural stage method of broaching a series of axially aligned bores, said method comprising in a first stage:

• providing a first elongated broach having a plurality of axially spaced, circumferentially extending cutting teeth, each cutting tooth being divided into arcuate segments with spaces between said segments, the arcuate segments of each cutting tooth being longitudinally aligned with the arcuate segments of the other cutting teeth,
• advancing said first broach through said bores and with said cutting teeth segments broaching arcuately spaced sectors of said bores but leaving unbroached ridges therebetween,
• said method further comprising in a second stage:
• providing a second elongated broach having a plurality of axially spaced cutting teeth,
• and advancing said second broach through said bores to broach the ridges left on said first stage,
• said second broach having a plurality of axially spaced pilot teeth to guide on the arcuately spaced sectors of said bores which were broached in the first broaching stage, said pilot teeth having reliefs to clear said ridges,
• and cutting teeth on said second broach dimensioned to clear said arcuately spaced sectors of said bores and to broach said ridges.

In apparatus for cutting a series of axially aligned and spaced bores wherein in a first stage arcuate sectors of said bores are removed leaving ridges therebetween after which said ridges are removed in a second stage, said apparatus comprising:

• an elongated broach for removing said ridges in the second stage,
• said broach having pilot means for piloting on the arcuate sectors of said bores removed in the first stage,
• said pilot means comprising a plurality of pilot teeth for piloting on the arcuate sectors,
• said pilot teeth having reliefs for clearing said ridges,
• and said broach having first cutting teeth dimensioned to clear said arcuate sectors and to broach said ridges.