ping jaws closed, and The accompanying figures represent anim- the pointing rollers moved the extreme length provement in Expansible Bits, for which a of their vibration, leaving the point of the patent was granted to Clinton L. Adancourt, spike formed. Similar letters refer to like of Troy, N. Y.,… … give the point. These dies resting above and The nature of this improvement consists in below against the disks of the pointing roll- making expansible bits for boring conical ers, form, as it were, grooves for the rollers holes any given distance into the material, to work in, against the sides of…
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