Hole cutter

Claim 2

A rotary hole cutter having a generally cylindrical annular wall provided with a plurality of axially extending cutting teeth spaced around the lower end thereof, the axial extent of said cutting teeth being substantially less than the axial extent of said wall, said cutting teeth having a generally radially extending cutting edge at the lower end thereof defined by the intersection of a front rake face and a bottom back off face, the rake angle of said front rake face being greater adjacent the radially inner end of said cutting edge than adjacent the radially outer end of said cutting edge.

Claim 3

A rotary hole cutter as called for in claim 1 wherein said cutting edge is defined by two generally straight portions comprising a radially inner portion which inclines downwardly and radially outwardly and a radially outer portion which inclines downwardly and radially inwardly.

Claim 4

A rotary hole cutter as called for in claim 1 wherein the rake angle of said front rake face adjacent the radially inner end of the cutting edge is at least about 20* and the rake angle of said front rake face adjacent the radially outer end of the cutting edge is not more than about 10*.

Claim 5

A rotary hole cutter as called for in claim 1 wherein said front rake face is defined by two radially spaced portions, the radially inner face portion having a generally uniform rake angle and the radially outer face portion having a generally uniform lesser rake angle.

Claim 6

A rotary hole cutter as called for in claim 4 wherein the rake angle of said radially inner face portion is at least about 20* and the rake angle of said radially outer face portion is not more than about 10*.

Claim 7

A rotary hole cutter as called for in claim 4 wherein the radial extent of the portion of the cutting edge having the greater rake angle is greater than the radial extent of the portion of the cutting edge having the lesser rake angle.

Claim 8

A rotary hole cutter as called for in claim 4 wherein said face portion having a greater rake angle has a radial extent adjacent the cutting edge of at least about 60 percent of the width of the tooth in a radial direction.

Claim 9

A rotary hole cutter as called for in claim 1 wherein said cutting edges are radially inclined so that the radially inner ends of the cutting edges are disposed in a plane above the radially outeR ends of said cutting edges.

Claim 10

A rotary hole cutter as called for in claim 4 wherein said cutting edges comprise two portions inclined radially in opposite directions and intersecting at a crest located intermediate the radially opposite ends of the cutting edges.

Claim 11

A rotary hole cutter as called for in claim 4 wherein at least some of said cutting edges comprise two radially adjacent portions which are radially inclined in opposite directions and which intersect in a crest which forms a lowermost portion of said cutting edges, said face portion of lesser rake angle extending radially inwardly beyond said crest.

Claim 12

A rotary hole cutter as called for in claim 10 wherein said face portion of lesser rake angle intersects said bottom back off face with an included angle of at least about 60* and said face portion of greater rake angle intersects said bottom back off face with an included angle of at least 40*.

Claim 13

A rotary hole cutter as called for in claim 11 wherein said back off face comprises two portions which are radially inclined in opposite directions and intersect along a line which is aligned circumferentially with said crest.

Claim 14

A rotary hole cutter as called for in claim 1 wherein the cutting edges when viewed in plan extend along lines which intersect the tangent at the outer periphery of the teeth at an angle of not greater than 90* on the forward side of each tooth.

Claim 15

A rotary hole cutter as called for in claim 13 wherein said sidewall is formed between successive teeth with an upwardly and radially outwardly extending gullet.

Claim 16

A rotary hole cutter as called for in claim 14 wherein said sidewall has a radially thickened lower edge in which said teeth are formed, said gullet extending from within said thickened edge upwardly into the portion of said wall above said thickened lower edge.

Claim 17

A rotary hole cutter as called for in claim 1 wherein said sidewall has a plurality of upwardly extending gullets around the outer face thereof, one gullet between each pair of successive teeth, said gullets inclining outwardly in an upward direction from the inner periphery of the wall of the cutter.

Claim 18

A rotary hole cutter as called for in claim 16 wherein each of said gullets inclines outwardly relative to the plane of said wall at an angle of not more than about 70*.

Claim 19

A rotary hole cutter as called for in claim 16 wherein each gullet is of progressively wider cross section in a radially outward direction.

Claim 20

A rotary hole cutter having a generally cylindrical annular wall provided with a plurality of axially extending cutting teeth spaced around the lower end thereof, the axial extent of said cutting teeth being substantially less than the axial extent of said wall, said wall having an upwardly extending gullet on the outer side thereof between successive teeth, the successive teeth having a clearance space therebetween and said gullets opening at their lower ends into said clearance spaces, said gullets extending upwardly beyond said teeth and being inclined radially outwardly in an upward direction from adjacent the inner periphery of said wall, said gullets also being inclined circumferentially rearwardly relative to the axis of the cutter, each of said teeth having a generally radially extending cutting edge at the lower end thereof, each of said cutting edges when viewed in plan extending along a line which intersects the tangent line at the outer periphery of the tooth at an angle less than 90* on the forward side of said tooth, the radially innermost portion of each cutting edge being inclined downwardly in a radially outward direction and the radially outermost portion of each cutting edge inclining downward in a radially inward direction.

Claim 21

A rotary hole cutter having a generally cylindrical annular wall provided with a plurality of axially extending cutting teeth spaced around the lower end thereof, the axial extent of said cutting teeth being substantially less than the axial extent of said wall, said wall having an upwardly extending gullet on the outer side thereof between successive teeth, the successive teeth having a clearance space therebetween and said gullets opening at their lower ends into said clearance spaces, said gullets extending upwardly beyond said teeth and being inclined radially outwardly in an upward direction from adjacent the inner periphery of said wall, said gullets also being inclined circumferentially rearwardly relative to the axis of the cutter, each of said teeth having a generally radially extending cutting edge at the lower end thereof, each of said cutting edges when viewed in plan extending along a line which intersects the tangent line at the outer periphery of the tooth at an angle less than 90* on the forward side of said tooth, the radially innermost portion of each cutting edge being inclined downwardly in a radially outward direction and the radially outermost portion of each cutting edge inclining downward in a radially inward direction.

Claim 22

A rotary hole cutter as called for in claim 19 wherein said wall comprises a radially thickened edge, said teeth being formed in said thickened edge with their radially outer ends extending outwardly beyond the pOrtion of the wall above said thickened edge and said gullets extending upwardly beyond said thickened edge.

Claim 23

A rotary hole cutter as called for in claim 20 wherein said teeth extend radially outwardly beyond the portion of the wall above said thickened edge a distance equal to at least about 25 percent of the tooth width.

Claim 24

A rotary hole cutter as called for in claim 20 wherein the outer surface portion of the wall above said thickened edge inclines radially inwardly in an upward direction.

Claim 25

A rotary hole cutter as called for in claim 20 wherein said teeth are progressively thinner in an upward direction and are progressively thinner in a direction from the forward to the trailing edges thereof.

Claim 26

A rotary hole cutter having a generally cylindrical annular wall provided with a plurality of axially extending cutting teeth spaced around the lower end thereof, the axial extent of said cutting teeth being substantially less than the axial extent of said wall, said teeth being divided into a plurality of successive groups, the successive teeth in one group corresponding in configuration with the successive teeth in the other groups, the teeth in each group having a generally radially extending cutting edge defined by the intersection of a front rake face and a bottom back off face, the cutting edges of each tooth comprising two radially adjacent portions which are radially inclined relative to one another and intersect at a crest so that each tooth is adapted to cut a generally V-shaped groove, the crests of the teeth in each group being staggered progressively radially and progressively upwardly so that the crest of the lead tooth in each group is located radially outermost and lowermost.

Claim 27

A rotary hole cutter having a generally cylindrical annular wall provided with a plurality of axially extending cutting teeth spaced around the lower end thereof, the axial extent of said cutting teeth being substantially less than the axial extent of said wall, said teeth being divided into a plurality of successive groups, the successive teeth in one group corresponding in configuration with the successive teeth in the other groups, the teeth in each group having a generally radially extending cutting edge defined by the intersection of a front rake face and a bottom back off face, the cutting edges of each tooth comprising two radially adjacent portions which are radially inclined relative to one another and intersect at a crest so that each tooth is adapted to cut a generally V-shaped groove, the crests of the teeth in each group being staggered progressively radially and progressively upwardly so that the crest of the lead tooth in each group is located radially outermost and lowermost.

Claim 28

A rotary hole cutter as called for in claim 24 wherein said front rake face of the lead tooth in each group comprises two radially adjacent portions, the radially innermost face portion having a rake angle greater than the radially outermost face portion, said face portion of lesser rake extending radially inwardly beyond the crest of said lead tooth.

Claim 29

A rotary hole cutter as called for in claim 25 wherein the radially outer ends of all the cutting edges are spaced from the axis of the tool the same radial distance and the radially inner ends of all the cutting edges are spaced from the axis of the tool the same radial distance.

Claim 30

A rotary hole cutter as called for in claim 26 wherein the radially outer ends of all the teeth lie in substantially the same horizontal plane and the radially inner ends of all the teeth lie in substantially the same horizontal plane.

Claim 31

A rotary hole cutter as called for in claim 24 wherein said annular wall has a radially thickened lower edge, said teeth being formed in said thickened edge, the radially inner portion of each cutting edge inclining downwardly and radially outwardly and said wall having around the outer periphery thereof an upwardly and radially outwardly inclined gullet between successive teeth, said gullets terminating at their upper ends in the portion of said wall above said thickened lower edge.

Claim 32

A rotary hole cutter as called for in claim 19 wherein the radially inner and outer portions of each cutting edge intersect in a crest which forms the lowermost portion of each cutting edge, the included angle between said cutting edge portions being at least 120*.