Abstract: A pressure or temperature gauge includes a Bourdon tube which is coupled via a shaft to transmit rotation to a stylus carried by the shaft which makes a record on a cylindrical chart which moves axially of the shaft at a constant rate. The shaft is divided into two sections which are joined together by a flexible coupling; the upper section of the shaft is mounted for angular displacement about its longitudinal axis by the thrust bearing. One section has an integrally formed axial extension which is received in a recess in the facing end portion of the other shaft section. This construction of the stylus shaft allows the angular motion produced by the coiling and uncoiling of the Bourdon type generally through an angle less than 360.degree. to be faithfully transmitted without any axial motion of the shaft which would give rise to erroneous recording of pressure or temperature readings in relation to time.

Abstract: A centralizing device for use down-well in maintaining an operational tool in a location accurately centralized in relation to the axis of the bore-hole irrespective of the angular orientation of the device and associated tool. The device comprises a shaft and at least three two-armed linkages angularly biased at their common axes towards the wall of the bore-hole by arrays of springs acting through slide blocks on the shaft. Axial movement of the blocks is limited by a central collar secured to the shaft.