This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
A common 6-in. mill file can be converted into a very useful tool for an amateur draftsman. Grind the end of the file as shown in the sketch and use it for prying out thumbtacks that are driven in too tightly. Grind the base of the tang into a knife blade for sharpening pencils, shaving chalk, opening envelopes, etc. Shape, by careful grinding, the part A for cutting and trimming sheets. Grind one edge of the file round and polish it for smoothing and burnishing purposes. Grind a sharp point on the tang for per- forating sheets. A piece of rubber stuck on the tang end answers the double purpose of a protector and eraser. The file part is used for finishing points on pencils.
Ill: A Tool Made of a File Combining Several Tools Which are Used by a Draftsman