Working Drawings

1. Working Drawings • The complete set of standardized drawings specifying the manufacture and assembly of a product based on its design. - completely describe the parts, both visually and dimensionally - show the parts in assembly - identify all the parts - specify standard parts. • Main Parts: a) detail drawings of each nonstandard part. b) an assembly or subassembly drawing showing all the standard and nonstandard parts in a single drawing. c) a bill of materials (BOM). d) a title block.

2. Detail Drawing • a dimensioned, multiview drawing of a single part, describing the part’s shape, size, material, and finish, in sufficient detail for the part to be manufactured based on the drawing alone. • Show all necessary dimensioned views needed to make the part. • Indicate material and tolerances. • Indicate any finish treatments (plating, etc.) and requirements for surface-finish roughness. • Standard parts are not drawn as details because they are normally purchased, not manufactured, for design. • It is often preferred to show just one part per sheet so the same part drawing can be included in multiple assemblies without confusion. • When more than one detail is placed on a sheet, the spacing between details is carefully planned, including leaving sufficient room for dimensions and notes.

3. Assembly Drawings • shows how each part of a design is put together. • If the design depicted is only part of the total assembly, it is referred to as a subassembly. • Not usually dimensioned unless here are dimensions that are critical to maintain during assembly. • Hidden lines not usually needed. • Types: • Outline assembly gives a general graphic description of the exterior shape. (simple assemblies only) • Sectioned assembly gives a general graphic description of the interior shape by passing a cutting plane through all or part of the assembly. (for complicated assemblies) • Pictorial assembly gives a general graphic description of each part, and uses center lines to show how the parts are assembled. (3-D CAD model in pictorial view)

4. Pictorial Assembly

5. Sectioned Assembly • Different hatch patterns indicate which part is which in the assembly section. • The material for the part can be identified by different hatch patterns. • The hatch patterns run at different angles on different parts in the assembly

6. Thin Parts Filled In Black • Thin parts like the gasket shown here are too small to hatch. • Parts like these are filled in solidly with black.

7. Parts Lists (Bill of Materials) • For each part: show part name, item number, material, and quantity needed for the assembly. • For standard parts, include the catalog number, and the company part number. • Parts List may be on a separate document • Identifying Part on drawing • Leader lines with balloons, assigning each part a detail number, in sequential order and keyed to the list of parts in the parts list. • Part No. may be Placed Directly on Drawing

9. Title blocks • Used to record all the important information necessary for the working drawings. • The title block is normally located in the lower right corner of the drawing sheet. • Almost All Engineering Firms Have Some Standard/Default Elements That are Included in all Engineering Drawings • Title blocks should contain the following: • Name and address of the company or design activity. • Title of the drawing. • Drawing number. • Names and dates of the drafters, checker, issue date, contract number, etc. • Predominant drawing scale. • Drawing sheet size letter designation. • Actual or estimated weight of the item. • Sheet number, if there are multiple sheets

10. Drawing SCALES • Typical Scale Callout SCALE 1:16 Length On DRAWING Length in REAL WORLD • Example: Scale: 1:2000 20 mm in drawing  length In REAL WORLD = 40 km

11. Architect/CE Scale • Recall Scale Definition Size on DRAWING Size in REAL WORLD • Example - Given Scale: 2” = 5’-0”

12. 1st and 3rd Angle Projections • THIRD Angle Projection - customarily used in the US. The front view is below the top, and to the left of the right-side view. • FIRST Angle Projection – used in Europe; essentially projects the “shadow” of an object onto a screen behind it. The top view is below the front view and the right-side view is to the left of the front view. • The projection used in the drawing should be indicated in the title block.

13. FIRST Angle Proj THIRD Angle Proj Projection used in drawing is indicated in Title Block.

14. Threaded Fasteners • Fastening is a method of connecting or joining two or more parts together, using processes or devices. • Threaded Fasteners use cylindrical surfaces with mating helical cuts Helical Threads Have Three Main Applications - Used to HOLD parts together • Used to ADJUST the Position of parts with reference to one another • - Used to TRANSMIT Power

15. Thread Terminology

16. Common Tread forms

17. Unified (USA) Thread Series • The Unified System (UN) Adopted on 18-Nov-1948 by the USA, UK , & Canada • Made fasteners Interchangeable • The UN Designation (Spec) has Two Main Elements • The Major (outside) Diameter • Specified by Either • A size No. running from 0-12 (0.06-0.216 inches) • The Major Dia, in Fractional inches (¼-4 inches) • The Inverse Pitch in Threads per Inch

18. UN Thread Series – 6 Total • COARSE Series (UNC or NC) • For General Use Where Rapid Assembly is Required • Threads Engage, or “Start” Easily • FINE Series (UNF or NF) • For Applications Requiring Greater Strength or Where the Length of Engagement is Limited • Used Extensively in Aircraft and Automobile Manufacturing

19. UN Thread Series – cont • EXTRA FINE Series (UNEF or NEF) • For Highly Stressed Parts • 8N Series (8N) • A Substitute for Coarse-Thread Series for Diameters larger Than 1” • All diameters have 8 threads per inch. Often Used on bolts for high pressure pipe applications.

20. UN Thread Series – cont.2 • 12N Series (12 UN or 12N) • A Continuation of the Fine-Thread Series for Diameters Larger than 1.5” • All diameters have 12 thds/in. Used in boiler work and in Machine Construction. • 16N Series (16 UN or 16N) • A Continuation of the ExtraFine-Thread Series for Diameters Larger than 2” • All diameters have 16 thds/in. Used on adjusting collars and other applications where thread must have fine adjustment regardless of diameter.

21. Screw Fastener Specification • Defaults That Need NOT be Part of Callout • NC or NF implied by Diameter & TPI • Class → Default is 2A or 2B • Hand → Default is RIGHT

22. UN Thread Classes • Two Types of Classes • Refers to EXTERNAL Threads (Bolts & Screws) • Refers to INTERNAL Threads (Nuts & “Tapped” holes) • Class Descriptions • Provide Liberal Allowance for Ease of Assembly Even When Threads are Dirty or Slightly Damaged • Not Commonly Used

23. UN Thread Classes cont • Class Descriptions cont. • For Commercially Produced bolts, screws, nuts, and other threaded fasteners • By Far the Most Common • Used in Precision Assemblies where a Close Fit is Required to WithStand Stress & Vibration • Typical Use is Aircraft or other Hi-Vibration Applications

24. Metric Thread Specification • Note That Pitch is Stated Explicitly • Compares to Inverse Pitch (TPI) for Unified Specification

25. Detailed Thread Representation • Used when diameter of thread is 1” or larger on plotted or Hand drawing. • Use ONLY When It is Important to Show the Function of the Thread • Not Typical for Hand Drawings

26. Simplified & Schematic Forms • Imply depth of thread with hidden lines for simplified representation • Use alternating LONG THIN & SHORT THICK lines to represent ROOT & CREST lines in schematic representation • Spacing is SCHEMATIC; need not Match Actual Pitch

27. Representation Comparison • Detailed → very tedious to construct • Not commonly used on Engineering Drawings • Simplified → fast but potentially confusing • Hidden lines can be mistaken for Object Features • Schematic → best overall • Fast, yet clearly shows the threads