GB1105214A - Improvements in or relating to measuring instruments - Google Patents

Abstract

1,105,214. Determining dimensions. A. G. WELLUM. Jan. 31, 1967 [Feb. 11, 1966], No. 6150/66. Heading G1M. A measuring instrument comprises a support member 14 on which is mounted a displaceable element 17 arranged for reciprocating movement in a predetermined direction in relation to the support member, against the action of flat springs 18, 19 biasing it to a predetermined rest position in relation to the support member, the displaceable element 17 being provided with first and second jaws 25, 28 one of which 25 is mounted on a micrometer 23 carried by the displaceable element for adjustment in the said predetermined direction of movement of the element, the spacing between the jaws being adjusted by the micrometer so that rotation of a cutting tool under tub mounted between the jaws will result in the displacement of the element 17 first in one sense and then in the opposite sense, and a gauge 30 co-operating with the displaceable element to provide an indication of the displacement of the element 17 to each side of its rest position. In operation an appropriate spindle extension 28 is fitted on an adapter 27 and the spacing between the spindle extension 28 and the micrometer spindle 25 is made less than the limiting diameter of the hole to be bored by 0.002 of an inch. The diameter of the cutting circle of the tool is checked by bringing it into position such that the cutting tool just touches the spindle extension. The tool is then rotated by hand in a reverse direction to its cutting direction so that the spindle 28 is first deflected in one sense with the displaceable element 17 and then the micrometer spindle in the opposite sense together with the displaceable element. The position of the casing 14 on the base-plate 12 is adjusted to give an equal deflection on the gauge 30 on either side of the zero and provided this deflection is 0.001 inch the cutting circle is correct.