tech 104 – technical graphics communication week 10: working drawings
TRANSCRIPT
TECH 104 – Technical Graphics Communication
Week 10:
Working Drawings
TECH 104 – Technical Graphics Communication
Week 10: Working Drawings
First, here’s what we talked about last time…
Applying Tolerances
TECH 104 – Technical Graphics Communication
Week 10: Working Drawings
∙ Tolerances are represented as Direct Limits (A) or as Tolerance Values (B).
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
TECH 104 – Technical Graphics Communication
Week 10: Working Drawings
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 oftolerances (written in decimals).
TECH 104 – Technical Graphics Communication
Week 10: Working Drawings
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.
TECH 104 – Technical Graphics Communication
Week 10: Working Drawings
Important Terms of Toleranced Parts
Allowance – the tightest fitbetween two mating parts.
(The minimum clearance or maximum interference).
TECH 104 – Technical Graphics Communication
Week 10: Working Drawings
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.
TECH 104 – Technical Graphics Communication
Week 10: Working Drawings
Important Terms of Toleranced Parts
Piece toleranceThe 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)
TECH 104 – Technical Graphics Communication
Week 10: Working Drawings
Fit Types:
A Clearance Fit occurs when two toleranced mating parts willalways leave a space or clearance when assembled.
An Interference Fit occurs when two toleranced mating parts willalways interfere when assembled.
TECH 104 – Technical Graphics Communication
Week 10: Working Drawings
Functional Dimensioning
Functional features are those that come in contact with other parts,especially moving parts. Holes are usually functional features.
Functional Dimensioning begins with tolerancing the most important features.
Then, the material around the holes isdimensioned (at a much looser tolerance).
TECH 104 – Technical Graphics Communication
Week 10: Working Drawings
Tolerance Stack-upOccurs when dimensions are takenfrom opposite directions of separateparts to the same point of an assembly.
Dimensionedfrom the
left.
Dimensionedfrom theright.
AVOID THIS!!!
TECH 104 – Technical Graphics Communication
Week 10: Working Drawings
Tolerance stack-up canbe eliminated by carefulconsideration and placement of dimensions.(Dimension from same side).
Better still, relate the twoholes directly to each other,not to either side of the part.The result will be the besttolerance possible of ±0.005.
AvoidingToleranceStack-up
Today’s Lecture - Week 10:Working Drawings
TECH 104 – Technical Graphics Communication
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 SinglePart 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 position2. 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 AssemblyDrawing of a Spring Pack containing…
TECH 104 – Technical Graphics Communication
Pictorial Assemblies
Sectioned Assembly
TECH 104 – Technical Graphics Communication
Pictorial Assemblies
Technical Illustration (Exploded) Assembly
TECH 104 – Technical Graphics Communication
Title Blocks
A. Name & Address of CompanyB. Title of the DrawingC. Drawing NumberD. Names and dates of drafters,
checker, issue date ,contract number, etc.
E. Design ApprovalF. Additional Approval BlockG. Drawing Scale H. Federal Supply Code for
ManufacturersJ. Drawing Sheet SizeK. Actual or estimated weightL. Sheet Number
…contain...
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.
Parts Lists
TECH 104 – Technical Graphics Communication
Revision BlocksRecord any changes - Found in upper-right corner
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
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)
Also in Today’s Lecture - Week 10:
Fastening Devices
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:
Internal Threads
External Threads
Form Chart
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.
TECH 104 – Technical Graphics Communication
Thread Representation:
TECH 104 – Technical Graphics Communication
General Types of Fasteners:
TECH 104 – Technical Graphics Communication
Finished vs.Unfinished Bolts:
The difference between a finished andUnfinished hex head bolt is a washerUnder the head of the finished bolt.
TECH 104 – Technical Graphics Communication
Nuts:
TECH 104 – Technical Graphics Communication
Cap Screws:
Notice the chamfer (Also found on bolts).
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:
TECH 104 – Technical Graphics Communication
Shoulder Screw:
Check Appendix 33 for the dimensions of the shoulder screwrequired 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:
TECH 104 – TechnicalGraphics Communication
This
Week’s
DrawingCreate a complete setof Working Drawings
TECH 104 – Technical Graphics Communication
Week 11:
Pictorial Drawings