Abstract: The invention relates to a novel tubular fitting member formed of a deformable material, such as steel, which may be combined with a helically wrapped wire screen to produce a mechanical seal of a gap formed adjacent the cut-off end portion of the screen when the screen is cut off perpendicular to its supports. Such cutting produces a loose, tapered wire tail which is normally broken off, thereby producing an open gap in the screen which is wider than the width of the slot between the wire wraps. The tubular fitting member has a groove formed in its outer surface closely adjacent to the screen end of the fitting. The groove defines the inner wall of a deformable flange which may be selectively forced toward the screen to close any gap formed adjacent its end during the cut-off operation.

Abstract: Abrasion cutting elements of a rotary drill bit are operatively connected to the bit body structure by means for yieldably supporting the abrasion cutting elements and for forcing them into a continuous drag mode of cutting contact with the earth formation. The drill bit may also employ compression or indentor cutting elements operatively attached in fixed operative positions. The yieldably supporting and force applying means may be hydraulically controlled by drilling fluid pressure and the cutting force applied on the abrasion cutting elements can be established independently of the axial cutting force transferred from the drill string and drill bit to the indentor cutting elements. Optimum performance of both the abrasion and indentor types of cutting elements is secured. The abrasion cutting elements are preferably retained for contacting and cutting the gage corner material.

Abstract: Abnormal drilling conditions are detected by monitoring mud volume of the mud system or rate of change of the mud volume. In one embodiment, makeup mud is automatically added to the system as solids are removed from the mud. Abnormal conditions are indicated by when the rate of makeup mud addition differs from the rate of solids removal. The mud system is maintained at a substantially constant volume by means of tanks specially constructed to provide a small mud/air interface.