APPENDIX I GLOSSARY When you enter a new occupation, you must learn the vocabulary of the trade in order to understand your fellow  workers  and  to  make  yourself  understood  by them.  Shipboard  life  requires  that  Navy  personnel  learn a relatively new vocabulary. The reasons for this need are many, but most of them boil down to convenience and safety. Under certain circumstances, a word or a few words mean an exact thing or a certain sequence of actions,  making  it  unnecessary  to  give  a  lot  of explanatory details. A great deal of the work of a technician  is  such  that  an  incorrectly  interpreted instruction   could   cause   confusion,   breakage   of machinery, or even loss of life.  Avoid this confusion and its attendant danger by learning the meaning of terms common to drafting. This glossary is not all-inclusive, but it does contain many terms that every craftsman should know. The terms given in this glossary may have more than one definition; only those definitions as related  to  drafting  are  given. ALIGNED  SECTION—A section view in which some internal features are revolved into or out of the plane of the view. ANALOG—The  processing  of  data  by  continuously variable  values. ANGLE—A figure formed by two lines or planes extending from, or diverging at, the same point. APPLICATION BLOCK—A part of a drawing of a subassembly showing the reference number for the drawing of the assembly or adjacent subassembly. ARC—A portion of the circumference of a circle. ARCHITECT’S SCALE—The   scale   used   when dimensions or measurements are to be expressed in feet  and  inches. AUXILIARY VIEW—An  additional  plane  of  an object, drawn as if viewed from a different location. It is used to show features not visible in the normal projections. AXIS—The center line running lengthwise through a screw. AXONOMETRIC   PROJECTION—A set of three or more views in which the object appears to be rotated at an angle, so that more than one side is seen BEND ALLOWANCE—An  additional  amount  of metal used in a bend in metal fabrication. BILL OF MATERIAL—A list of standard parts or raw materials  needed  to  fabricate  an  item. BISECT—To divide into two equal parts. BLOCK DIAGRAM—A diagram in which the major components of a piece of equipment or a system are represented   by   squares,   rectangles,   or   other geometric   figures,   and   the   normal   order   of progression of a signal or current flow is represented by lines. BLUEPRINTS —Copies of mechanical or other types of  technical  drawings.   Although  blueprints  used  to be blue, modem reproduction techniques now permit  printing  of  black-on-white  as  well  as  colors. BODY PLAN—An end view of a ship’s hull, composed of superimposed frame lines. BORDER  LINES—Darklines defining the inside edge of the margin on a drawing. BREAK LINES—Lines to reduce the graphic size of an  object,  generally  to  conserve  paper  space.  There are two types: the long, thin ruled line with freehand zigzag  and  the  short,  thick  wavy  freehand  line. BROKEN  OUT  SECTION—Similar to a half section; used when a partial view of an internal feature is sufficient. BUTTOCK  LINE—The    outline    of    a    vertical, longitudinal section of a ship’s hull. CABINET  DRAWING—A type of oblique drawing in which the angled receding lines are drawn to one-half  scale. CANTILEVER—A   horizontal   structural   member supported only by one end. CASTING—A metal object made by pouring melted metal into a mold CAVALIER   DRAWING—A form of oblique drawing in which the receding sides are drawn full scale, but at 45° to the orthographic front view. AI-1