Scribing apparatus and method

6) A method of marking a line on a surface of a workpiece at a selected distance from a datum edge of the workpiece, the method comprising the steps of:

• attaching a scribe retaining apparatus for sliding motion along a ruling blade of a geometrical instrument that comprises the ruling blade and a stock having a guide surface adapted to be brought into abutting contact with the datum edge;
• holding the stock of the geometrical instrument against the datum edge at an angle selected so that a first, flat, portion of a bottom of the scribe retaining apparatus abuts the surface of the workpiece, whereby a working tip of a scribe retained in the scribe retaining apparatus is held adjacent to, but out of contact with, the surface of the workpiece;
• sliding the scribe retaining apparatus axially along the ruling blade until the working tip of the scribe is at the selected distance from the datum edge of the workpiece;
• locking the scribe retaining apparatus to the ruling blade;
• rotating the stock of the geometrical instrument about an axis of the blade to bring a second portion of the bottom of the scribe retaining apparatus into contact with the surface of the workpiece, and to thereby bring the working tip of the scribe into operative marking contact with the workpiece;
• and
• sliding the stock of the geometrical instrument along the datum edge to mark the line at the selected distance therefrom.

10) An apparatus for guiding a scribe along a straight line at a selected distance from a datum edge of a workpiece, the apparatus comprising, in combination:

• a geometrical instrument comprising a ruling blade and a stock, the stock having a guide face perpendicular to the ruling blade;
• and
• a scribe retaining apparatus attached to the ruling blade for motion therealong, the scribe retaining apparatus comprising a locking device for locking the scribe retaining apparatus to the ruling blade at a position selected so that a working tip of the scribe is at the selected distance from the datum edge;
• wherein the scribe retaining apparatus further comprises two flat bottom surface portions meeting along a separation line that is perpendicular to the guide face of the geometrical instrument when the scribe retaining apparatus is attached to the ruling blade, a first of the flat bottom portions disposed parallel to the ruling blade and the second of the two flat bottom portions slanted with respect to the ruling blade.