DEC STD 114

This document, DEC STANDARD 114, Section 0, Revision A, dated 7-Oct-82, outlines Digital Equipment Corporation's (DEC) requirements for engineering drawings, divided into two main sections:

1. Section 0: Industry Standards Adopted by Digital Engineering and Manufacturing Organizations

   • Purpose: To list and establish the specific industry standards adopted by Digital as the basis for its engineering drawing practices. This ensures consistent application across Digital's engineering and manufacturing organizations.
   • Content: It details Digital's policy to adopt and use existing industry standards, documenting any exceptions. Key adopted standards are listed, primarily ANSI (American National Standards Institute) standards covering various aspects of engineering drawings such as:
     • Multi and Sectional View Drawings (ANSI Y14.3)
     • Pictorial Drawings (ANSI Y14.4)
     • Dimensioning and Tolerancing (ANSI Y14.5)
     • Screw Thread Representation (ANSI Y14.6)
     • Gear, Forging, Welding, and Casting drawing standards.
   • Responsibility: Standards and Methods Control is responsible for the content and approval of changes, while project engineers ensure compliance.

2. Section 1: Dimensioning and Tolerancing on Engineering Drawings

   • Purpose: To present Digital's specific requirements and guidelines for representing dimensions and dimension tolerances on engineering drawings.
   • Content: This section provides detailed rules and practices for:
     • Units of Measure: Allows U.S. customary (inch), metric (millimeters), or dual (inch and metric) dimensioning, with dual preferred for customer-facing drawings.
     • Decimal Dimensioning: Preferred for all new product drawings, with specific rules for decimal place sensitivity based on tolerance, and how tolerances should be displayed.
     • Tolerancing: Digital uses two methods: "Number of Decimal Places Sensitive" and "Dimension Sensitive" (preferred for consistent design accuracy).
     • Fractional Dimensioning: Generally not allowed on new parts documentation due to conversion difficulties and legibility issues with microfilm. Existing fractional drawings must be converted to decimal upon revision.
     • Title Blocks: Standard Digital title blocks are used to specify general tolerances, with options for different decimal or dimension-sensitive formats.
     • Conversions: Provides explicit rules for converting inch dimensions to metric and fractions to decimal, including rounding guidelines.
     • Primary Standard: Digital primarily adopts ANSI Y14.5-1973 for dimensioning and tolerancing, supplemented by an internal guide.
     • Projection: Third angle projection is the standard throughout Digital.

In essence, DEC STANDARD 114 serves as Digital's comprehensive internal guide for creating and managing engineering drawings, standardizing practices based on recognized industry standards while also defining specific internal requirements for dimensioning, tolerancing, and documentation formats.