Compressor 1 delivers compressed air through water-type air-pressure stabilizer 2 and restrictor a into measuring chamber 3 which is connected to measuring head 4. This head has measuring nozzle 5 on whose carefully lapped end face work 6 rests with its surface whose roughness is to be checked. The work is held against the nozzle by the spindle of vertical comparator 7. The spindle has a spherical tip. The measuring head and the comparator spindle are strictly coaxial and are mounted on a common stand. The pressure in chamber 3, measured by water-column manometer 8, is an indication of the size of the surface irregularities. The manometer scale is graduated according to standard specimens.
$3713$SHP,M$