GB190812922A - A Micrometer for use with Surface Gauge. - Google Patents

Abstract

12,922. Comyn, D. A. June 17. Gauges.-A device attached to the bar of a surface gauge for measuring variations in height consists of a circular box of magnalium in which slides a rod e carrying a pulley p. Around the pulley a silk thread is led, one end of which is attached to the tensioning - spring f and passes a number of times round the pointer spindle b, the middle turn being jammed in sawcuts in a washer c secured to the spindle. The other end of the thread is attached to a shed on a lever g which can be adjusted so as to alter the direction of the latter end of the thread and therefore the value of the movement of the rod in turns of the pointer spindle, this adjustment enabling a standard movement such as the tenth of an inch of the rod to be made equal to a complete turn of the pointer. The dial scale has a hundred divisions, and the rotatable cover glass has a mark i of black paper attached to it. A pin on the rod works in a guide h to prevent the rod from turning, and a nut is provided on the screwed end to facilitate setting to zero. In a modification, the rod may have a pair of pulleys around which and an additional fixed pulley the thread passes giving greater sensibility. The tensioning-spring f has a narrow looped end to take a knot in the thread and is coiled round and secured to the split plug q which is set to adjust the tension by means of a screwdriver. An eyelet and clamping-screw are fitted to the hinged cover for attachment to the bar of a scribing-block.