Abstract: A well jar is characterized by inner and outer telescoped members held from relative displacement by a latching member having an extending portion thereon. Imposition of an axially directed triggering force exceeding a predetermined magnitude is transmitted against the biasing force of a resilient member through a force transmitting arrangement to a latch release member provided with an opening therein sized to receive the extending portion of the latching member. The release member rotates in a predetermined angular direction to come into registry with the opening therein to receive the extending portion of the latching member as the latching member displaces radially outwardly to release the inner member. Upon release, the inner member responds to the axially directed force to drive impact surfaces disposed on the inner and outer members into an impact-producing engagement.

Abstract: A rotary drill bit for drilling earthen formations is provided with a plurality of discrete cutting teeth disposed on the lower face of the bit body and arranged in circumferentially spaced, generally radially extending rows. Each of the teeth has a large diamond (or a diamond-like material) set in its leading face at its peak and may have the balance of its leading face as well as its sides provided with smaller flush mounted diamonds. Alternatively, the teeth can be provided with a synthetic diamond or a sintered diamond facing which can extend to the peaks thereof. Fluid courses extend from a central passage in the bit along the leading faces of the teeth so as to discharge fluid against these leading faces and wash the cuttings away therefrom into the valleys between adjacent ones of the teeth.