Title: Longitudinal axis roller drill bit with gage inserts protection

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Abstract: A Zublin type rotary drill bit is disclosed having a main body rotating about a main axis. The bit body includes a journl pin extending downwardly therefrom, with the journal pin forming a second axis disposed at an angle with respect to the main axis. The journal pin has a cutter rotatively mounted thereon, with the cutter having a spherical outer surface which has a plurality of inner rows of tungsten carbide mounted thereon. The gage row of the cutter is also formed on the spherical outer surface and defines a plane intersecting the intersection of the main and second axes. The cutter gage row is formed by a plurality of inserts having synthetic diamond cutting surfaces, which are facing downwardly toward the apex of the cutter, in order to scrape the sides of the bore hole during the downwardly traveling portion of the gage insert travel cycle. The cutter also has a heel portion which is located adjacent the backside of the gage inserts for protecting the inserts during the upwardly traveling portion of the gage insert travel cycle.


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