Apparatus and method of measuring surface roughness

An apparatus for measuring the finish of the interior surface of a fastener hole comprising:

• a case;
• a probe containing a stylus and transducer therein to convert vertical motions of said stylus as it traverses surface irregularities into electrical signals by said transducer, said probe mounted to a carriage means slidably mounted within said case;
• a pilot adapted to removably fit upon said case, said pilot containing a cylindrical extension thereupon with a diameter substantially equal to that of a fastener hole and adapted to fit within said hole, said extension containing a hole therein to encompass said stylus and probe such that when said extension is inserted into said fastener hole said stylus and probe pass through said hole and contact the interior portion of said fastener hole;
• reciprocating means contained within said case, said means secured at one end to said carriage and at the other end to said case, said reciprocating means adapted to slidably move said carriage means within said case;
• means for determining the position of said carriage means as said carriage means slidably moves within said case;
• means for electronically presetting the position of said carriage;
• means for electronically comparing the position of said carriage means with a plurality of selectable carriage positions, said means causing said carriage means to slidably reverse its direction of travel when said carriage means reaches said positions;
• and
• means for displaying said electrical signals produced by said stylus and said transducer.