Bearing for the barrel screw of a sextant

摘要

To improve the angular measuring accuracy in a sextant, a two-point bearing for the bearing block (6) of the barrel screw (5, 9, 10) is proposed which is made possible by the fact that the outside free end of the index lever (4) is constructed to be U-shaped encircling the bearing block (6) so that two bearing surfaces are available for the bearing block (6). A bearing without clearance is ensured by V-ways (161, 162) in the bearing block (6) which are engaged by steel balls (151, 152) which are adjustable by means of holding and adjustment screws (171, 172). The result is that the barrel screw is spatially fixed without clearance in three planes and the reproducible measuring accuracy can be improved to an angle of