The principles of detail drawings having been thoroughly discussed in the preceding pages, the general system to be followed in preparing shop drawings for the workman's use will now be outlined and illustrated.
As previously stated, for a new machine, the original sketches will be supplied by the designer, and it is the duty of the detail draftsman to read and interpret them; or the designer may furnish a rough general layout to scale, from which the detail draftsman must pick out the details, scaling off the dimensions.
Oftentimes certain details of an existing machine have to be copied, in which case the sketches will have to be made by the detail draftsman himself, from the machine. Proficiency in the art of making sketches is a very valuable and necessary acquisition for any draftsman. Accuracy, completeness, clearness, and rapidity in making are the principal requirements for a good sketch.
The sketches should be made so clear, that even if they are laid aside for a long time they can be readily understood without depending at all upon memory. There is a strong tendency for the beginner to make his sketches hurriedly, thinking that when he comes to finish his drawing he can supply the details from memory. This is a bad plan and will lead to many mistakes. The sketches must be so clear and complete that anyone can read them who has never seen the machine. No attempt need be made to draw them to scale, but all dimensions, carefully measured from the machine, should be placed on the sketch.