A drafting machine for use with a drafting table having a drawing surface, which comprises:
- a protractor head adapted to be movably mounted on a drafting table such as to permit horizontal and vertical movement of the protractor head along the drawing surface of the drafting table;
- an elongated first mounting means rotatably mounted on the protractor head and having an elongated first reference scale, the longitudinal axis of the first reference scale being parallel to the longitudinal axis of the first mounting bar;
- an elongated second mounting means slidably mounted on the first mounting means with the longitudinal axis of the second mounting means being perpendicular to the longitudinal axis of the first mounting means, the second mounting means having an elongated second reference scale, the longitudinal axis of the second reference scale being parallel to the longitudinal axis of the second mounting means;
- first and second elongated straight edges, said first straight edge being slidably mounted with respect to the second mounting means and the second straight edge, the longitudinal axis of the first straight edge being parallel to the first mounting means and being perpendicular to the longitudinal axis of the second mounting means and to the second straight edge, the first straight edge being alignable with the reference scale of the second mounting means;
- said second straight edge being mounted on the second mounting means so as to be slidably mounted with respect to the first mounting means, the longitudinal axis of the second straight edge being perpendicular to the longitudinal axis of the first mounting means, the second straight edge being alignable with the first reference scale;
- top, bottom, and center rails, each having a respective rack therealong;
- first mounting means for mounting the top and bottom rails on the drafting table in parallel spaced relation;
- second mounting means for mounting the center rail on the top and bottom rails for movement therealong with the center rail perpendicular to the top and bottom rails;
- a carriage guided along the center rail and carrying said protractor head;
- first adjusting means on the carriage normally arranged to operate with the rack on the center rail for finely adjusting and setting the position of the carriage lengthwise of the center rail;
- second adjusting means on the center rail normally arranged to operate with the racks on the top and bottom rails simultaneously for finely adjusting and setting the position of the center rail lengthwise of the top and bottom rails;
- first and second deactivating means for selectively deactivating said first and second adjusting means, respectively;
- and
- first and second biasing means opposing deactivation by said deactivating means, said center rail being adapted to be moved freely along the top and bottom rails when the second adjusting means is deactivated, and said carriage being adapted to be moved freely along the center rail when the first adjusting means is deactivated.