CHAPTER 3
GENERAL DRAFTING PRACTICES
Overview
Introduction
Before 1955, Navy draftsmen were divided into six specialties: mechanical
(DMM), structural (DMS), electrical (DME), topographical (DMT),
lithographic (DML), and illustrative (DMI). Over the years, lithographic
draftsmen became Lithographer’s Mates (LI) and the draftsman rating
polarized into two distinct camps referred to as straight-line draftsmen and
illustrative draftsmen. Straight-line draftsmen formed the construction rating
Engineering Aid (EA) and artists formed the Illustrator Draftsman (DM) rating.
DMs maintain strong ties to their mechanical/mathematical foundations even
today. Because a good draftsman is rarely unemployed, you should learn the
fundamentals of drafting to improve your skills and marketability.
Objectives
The material in this chapter enables you to do the following:
Define standard drafting terminology.
Identify drafting standards and practices.
Follow the standard order of inking.
Identify common line conventions.
Differentiate between line resolutions.
Correctly dimension drawings with multiple parallel dimensions.
Dimension radii and other rounded surfaces.
Define tolerance and the differences between size, allowance, and fit.
Understand the basic hole and basic shaft theory.
Select regular and necessary views.
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