TECH 104 – Technical Graphics Communication Week 10: Working Drawings

TECH 104 – Technical Graphics Communication First, here’s what we talked about last time… Applying Tolerances Week 10: Working Drawings

Representing Tolerance Values TECH 104 – Technical Graphics Communication Representing Tolerance Values ∙ Tolerance is the total amount a dimension may vary and is the difference between the maximum and minimum limits. (A) Tolerance = .04 (B) Tolerance = .006 ∙ Tolerances are represented as Direct Limits (A) or as Tolerance Values (B). Week 10: Working Drawings

Important Terms of Toleranced Parts TECH 104 – Technical Graphics Communication Important Terms of Toleranced Parts A System is two or more mating parts. Nominal Size is used to describe the general size (usually in fractions). Basic Size – theoretical size used as a starting point for the application of tolerances (written in decimals). Week 10: Working Drawings

Important Terms of Toleranced Parts TECH 104 – Technical Graphics Communication Important Terms of Toleranced Parts Limits – the maximum and minimum sizes shown by the tolerance dimension. The large value on each part is the Upper Limit, the small value = Lower Limit. Actual Size is the measured size of the finished part after machining. Week 10: Working Drawings

Important Terms of Toleranced Parts TECH 104 – Technical Graphics Communication Important Terms of Toleranced Parts Allowance – the tightest fit between two mating parts. (The minimum clearance or maximum interference). Week 10: Working Drawings

Important Terms of Toleranced Parts TECH 104 – Technical Graphics Communication Important Terms of Toleranced Parts Maximum Material Condition (MMC) The condition of a part when it contains the greatest amount of material. Least Material Condition (LMC) The condition of a part when it contains he least amount of material possible. Week 10: Working Drawings

Important Terms of Toleranced Parts TECH 104 – Technical Graphics Communication Important Terms of Toleranced Parts Piece tolerance The difference between the upper and lower limits of a single part (.002 on the insert in this example, .004 on the slot.). System tolerance The sum of all the piece tolerances. For this example (.006) Week 10: Working Drawings

Fit Types: TECH 104 – Technical Graphics Communication A Clearance Fit occurs when two toleranced mating parts will always leave a space or clearance when assembled. An Interference Fit occurs when two toleranced mating parts will always interfere when assembled. Week 10: Working Drawings

Functional Dimensioning TECH 104 – Technical Graphics Communication Functional Dimensioning Functional Dimensioning begins with tolerancing the most important features. Then, the material around the holes is dimensioned (at a much looser tolerance). Functional features are those that come in contact with other parts, especially moving parts. Holes are usually functional features. Week 10: Working Drawings

Tolerance Stack-up AVOID THIS!!! TECH 104 – Technical Graphics Communication Occurs when dimensions are taken from opposite directions of separate parts to the same point of an assembly. Tolerance Stack-up Dimensioned from the left. Dimensioned from the right. AVOID THIS!!! Week 10: Working Drawings

Avoiding Tolerance Stack-up TECH 104 – Technical Graphics Communication Avoiding Tolerance Stack-up Better still, relate the two holes directly to each other, not to either side of the part. The result will be the best tolerance possible of ±0.005. Tolerance stack-up can be eliminated by careful consideration and placement of dimensions. (Dimension from same side). Week 10: Working Drawings

Today’s Lecture - Week 10: Working Drawings TECH 104 – Technical Graphics Communication Today’s Lecture - Week 10: Working Drawings Generally, a complete set of Working Drawings for an assembly includes: 1.) Detail Drawings of each non-standard part. 2.) An Assembly or Subassembly drawing showing all the standard parts in a single drawing. 3.) A Bill of Materials (BOM). 4. A Title Block.

A Detail Drawing of a Single Part Called a Lever

Assembly Drawing of a Piston & Rod containing 8 parts. An assembly drawing normally consists of the following: 1. All parts drawn in their operating position 2. A parts list or Bill of Materials (BOM) 3.Leader lines with balloons indicating all parts. 4. Machining and assembly instructions

Detail Drawing of the retainer ring used to fasten the rod to the piston.

Drawing Number Part Numbers Multiview Sectioned Assembly Drawing of a Spring Pack containing… Drawing Number Part Numbers

Pictorial Assemblies TECH 104 – Technical Graphics Communication Sectioned Assembly Pictorial Assemblies

Pictorial Assemblies TECH 104 – Technical Graphics Communication Technical Illustration (Exploded) Assembly

Title Blocks …contain... TECH 104 – Technical Graphics Communication Name & Address of Company Title of the Drawing Drawing Number Names and dates of drafters, checker, issue date , contract number, etc. E. Design Approval F. Additional Approval Block G. Drawing Scale H. Federal Supply Code for Manufacturers J. Drawing Sheet Size K. Actual or estimated weight L. Sheet Number

Parts Lists TECH 104 – Technical Graphics Communication The information normally included in a parts list is as follows: 1. Name of the part. 2. A detail number for the part in the assembly. 3. The part material, such as cast iron or bronze. 4. The number of times that part is used in the assembly. 5. The company assigned part number. 6. Other information, such as weight, stock size, etc.

Revision Blocks TECH 104 – Technical Graphics Communication Record any changes - Found in upper-right corner Revision Blocks

General tolerance note for inch and millimeter dimensions TECH 104 – Technical Graphics Communication General tolerance note for inch and millimeter dimensions

ANSI drawing sheets with “zones” located on the border.

TECH 104 – Technical Graphics Communication Tabular Drawings

Also in Today’s Lecture - Week 10: Fastening Devices Fastening is a method of connecting or joining two or more parts together, using devices or processes. Mechanical Fastening –Process that uses manufactured devices (Nuts and Bolts) Bonding – Using material (Glue, Welding) Forming – Using component shape itself (HVAC, Tupperware, Velcro)

Threaded Fasteners First Application of a screw thread was developed by Archimedes to lift water. 1800’s Joseph Whitworth – English Standard Screw Threads 1864 – US Screw Thread Standard 1946 – ISO Develops Metric Standard 1948 – US Develops Unified Standard

Standard Thread Notations: Form Chart Standard Thread Notations: Internal Threads External Threads

Specifying Tap Drill Size: TECH 104 – Technical Graphics Communication Specifying Tap Drill Size: A Tap is a tool used to make threads in holes. A Die is used to make external threads.

Thread Representation: TECH 104 – Technical Graphics Communication Thread Representation:

General Types of Fasteners: TECH 104 – Technical Graphics Communication General Types of Fasteners:

Finished vs. Unfinished Bolts: TECH 104 – Technical Graphics Communication Finished vs. Unfinished Bolts: The difference between a finished and Unfinished hex head bolt is a washer Under the head of the finished bolt.

TECH 104 – Technical Graphics Communication Nuts:

Cap Screws: TECH 104 – Technical Graphics Communication Notice the chamfer (Also found on bolts).

A ½” Hex Head Machine Screw is used on this week’s assembly drawing. TECH 104 – Technical Graphics Communication Machine Screws: Machine Screws are finished with flat bottoms instead of chamfered corners. A ½” Hex Head Machine Screw is used on this week’s assembly drawing.

TECH 104 – Technical Graphics Communication Set Screws:

Shoulder Screw: TECH 104 – Technical Graphics Communication Check Appendix 33 for the dimensions of the shoulder screw required for this week’s assembly drawing

TECH 104 – Technical Graphics Communication Retaining Rings:

TECH 104 – Technical Graphics Communication Lock Washers:

TECH 104 – Technical Graphics Communication Pin Types:

TECH 104 – Technical Graphics Communication Standard Key Types:

TECH 104 – Technical Graphics Communication Rivets:

TECH 104 – Technical Graphics Communication Rivets:

TECH 104 – Technical Graphics Communication Springs:

This Week’s Drawing TECH 104 – Technical Graphics Communication Create a complete set of Working Drawings

TECH 104 – Technical Graphics Communication Week 11: Pictorial Drawings