Excerpt from The Sparrett Book for Machinists Apprentices
Laying out work preliminary to machining is transferring blue-print instructions on to the metal. While the blue-print gives dimensions accurately, without any great precision in the drawing itself, lines laid out on the metal are to be worked to and must therefore be accurate. No one can consider himself a skilled machinist unless he can lay out his own work and, when called upon, lay out work for the less experienced.
To become skilled in laying out should be the aim of every apprentice. Possessing this skill gives more opportunity to show ability than the running of a machine. It is a qualification one must have for advanced positions such as toolmaker, foreman, or superintendent.
But laying out requires some knowledge of mathematics, some skill at mechanical drawing, and an acquaintance with machinists' fine tools and shop operations. Attention to details and extreme care are of utmost importance. Increased labor cost, as well as material wasted because of errors in laying out, are the penalties of mistakes.
The apprentice, then, should lose no opportunity to make himself capable of laying out work. Close observation of pieces laid out by skilled machinists is one way of becoming acquainted with the art. The fortunate apprentice may also have opportunity to observe a skilled machinist while laying out various jobs.
The number of measuring and laying out tools or instruments now purchasable is very great and the apprentice must become familiar with practically all of them. He must know what he can accomplish with each so that he will instinctively select those best suited to the job in hand.
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