This section is from the book "Machine Shop Work", by Frederick W. Turner, Oscar E. Perrigo, Howard P. Fairfield. Also available from Amazon: Machine shop work.
Chipping is a term applied to the removal of metal with the cold chisel and hammer. The degree of accuracy required varies. The piece is held in a vise, and the method of working is to grasp the chisel firmly with the left hand, holding the cutting edge to the work and striking the head of the chisel with the hammer, keeping the eyes on the edge of the chisel to watch the progress of the work, Fig. 47. The lower side, or bevel of the chisel, is the guiding surface and is held at a very slight angle with the finished portion of the work, the cutting edge only touching. Raising or lowering the shank of the chisel increases or decreases the inclination of the guiding bevel and causes the chisel to take a heavier or lighter cut. If the hand is carried too low, the chisel will run out before the end of the cut; while if the hand is raised too high, the progress will be slow, owing to the resistance offered by the metal to separation. The depth of the cut taken with a cold chisel should never be more than an eighth of an inch.
Fig. 47. Bench Chipping.
When chipping wrought iron or steel, a piece of waste saturated with oil should be kept on the bench and the edge of the chisel frequently thrust into it. This lubricates the surfaces in contact and preserves the cutting edge of the chisel. While lines are used as guides in chipping operations, it is never advisable to bring the surfaces too near them with the chisel; sufficient stock must be left so that the surfaces may be finished with a file. This is especially to be observed in chipping keyways with a cape chisel; an ample margin for filing should be left both on the sides and on the bottom.