Figure 1-6.Use of standard lines.

Bill of Material

Shipboard Blueprints

Blueprint Reading and Sketching - Intro to drafting and architecture practices
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number of the next larger assembly of which the smaller unit or assembly is a part. The USED ON column shows the model number or equivalent designation of the assembled units part. FINISH MARKS Finish marks (P) used on machine drawings show surfaces to be finished by machining (fig. 1-6). Machining provides a better surface appearance and a better fit with closely mated parts. Machined finishes are NOT the same as finishes of paint, enamel, grease, chromium plating, and similar coatings. NOTES AND SPECIFICATIONS Blueprints show all of the information about an object or part graphically. However, supervisors, contractors, manufacturers, and craftsmen need more information that is not adaptable to the graphic form of presentation. Such information is shown on the drawings as notes or as a set of specifications attached to the drawings. NOTES are placed on drawings to give additional information to clarify the object on the blueprint (fig. 1-2). Leader lines show the precise part notated. A SPECIFICATION is a statement or document containing a description such as the terms of a contract or details of an object or objects not shown on a blue print or drawing (fig. 1-2). Specifications describe items so they can be manufactured, assembled, and maintained according to their performance require- ments. They furnish enough information to show that the item conforms to the description and that it can be made without the need for research, development, design engineering, or other help from the preparing organization. Federal specifications cover the characteristics of material and supplies used jointly by the Navy and other government departments. LEGENDS AND SYMBOLS A legend, if used, is placed in the upper right corner of a blueprint below the revision block. The legend explains or defines a symbol or special mark placed on the blueprint. Figure 1-2 shows a legend for an electrical plan. THE MEANING OF LINES To read blueprints, you must understand the use of lines. The alphabet of lines is the common language of the technician and the engineer. In drawing an object, a draftsman arranges the different views in a certain way, and then uses different types of lines to convey information. Figure 1-6 shows the use of stan- dard lines in a simple drawing. Line characteristics Figure 1-6.—Use of standard lines. 1-7

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