Cutter of a boring head, hub for the cutter and method of manufacturing such a hub

A hub for a cutter of a boring head, said cutter being rotatably mounted, via a shaft of the cutter, in a saddle secured to the boring head, said hub, comprising:

• a roller bearing means,
• at least one outer race for a set of tapered rollers of the roller bearing means,
• said outer race being integral with the hub,
• said outer race having an axial extension at a certain angle relative to a longitudinal center axis of the shaft, said angle being so oriented that an axially inner portion of said outer race is located more closely to the longitudinal center axis of the shaft than an axially outer portion of said outer race.

A method of manufacturing a hub for a cutter of a boring head, said cutter being rotabably mounted, via a shaft of the cutter, in a saddle secured to the boring head, said hub being rotatable relative to the shaft via a roller bearing means, comprising the steps of:

• creating a blank of the hub by suitable machining,
• machining portions of the hub that are to be hardened to an almost finished shape while portions of the hub that are not to be hardened are left with an additional layer of a few millimeters,
• subjecting the blank to carburizing,
• again machining the blank to remove the additional layer,
• heat-treating the blank in order to harden the portions having the almost finished shaped, and
• subjecting the outer races to further surface treatment in order to comply with tolerances.

A method of manufacturing a hub for a cutter of a boring head, said cutter being rotatably mounted, via a shaft of the cutter, in a saddle secured to the boring head, said hub being rotatable relative to the shaft via a roller bearing means, comprising the steps of:

• creating a blank of the hub by suitable machining,
• machining the hub to an almost finished shape,
• applying a layer that prevents carburization to portions of the hub that are not to be hardened,
• subjecting the blank to carburizing,
• heat-treating the blank in order to harden the portions that are not having a layer to protect against carburization, and
• subjecting the outer races to further surface treatment in order to comply with tolerances.

A hub for a cutter of a boring head, said cutter being rotatably mounted, via a shaft of the cutter, in a saddle secured to the boring head, said hub, comprising:

• a hub body,
• roller bearing means,
• at least one outer race for a set of tapered rollers of the roller bearing means,
• carrying means for carrying a cutter on an outer circumferential surface of the hub body,
• said outer race being integral with the hub body,
• said outer race having an axial extension at a certain angle relative to a longitudinal center axis of the shaft, said angle being so oriented that an axially inner portion of said outer race is located more closely to the longitudinal center axis of the shaft than an axially outer portion of said outer race.