Rock bit insert
Patent 4869329 Issued on September 26, 1989. Estimated Expiration Date: 
August 31, 2008. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
August 31, 2008. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 2687875 2731710 3581835 Earth boring tool with improved inserts Method for extending the life of a cutting tool Patent #: 4674365 InventorsAssigneeApplicationNo. 07/239162 filed on 08/31/1988US Classes:175/57, PROCESSES175/426, Insert76/108.2Rock drillExaminersPrimary: Neuder, William P.Attorney, Agent or FirmInternational ClassesB22F 3/24 (20060101)B23P 15/28 (20060101) E21B 10/46 (20060101) E21B 10/52 (20060101) E21B 10/56 (20060101) AbstractA new and improved tungsten carbide insert for rock bits is disclosed, in which the inserts are subject to extended vibratory tumbling in order to increase their fracture toughness. More specifically the vibratory finishing or tumbling of the inserts has been increased from a typical time of 30-60 minutes to time periods of at least 90 minutes and preferably a minimum of 225 minutes. A marked improvement in toughness is obtained by this process because the size and distribution of surface flaws of the inserts were greatly reduced, and because the surface hardness of the inserts was increased, thereby resulting in an increase in the stress required to cause fracture, and a consequent increase in resistance to breakage.Other References
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