TECH 104 – Technical Graphics Communication

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# TECH 104 Technical Graphics Communication - PowerPoint PPT Presentation

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. TECH 104 – Technical Graphics Communication. Representing Tolerance Values.

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Week 10:

Working Drawings

### TECH 104 – Technical Graphics Communication

First, here’s what we talked about last time…

Applying Tolerances

Week 10: Working Drawings

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

A System is two or more mating parts.

TECH 104 – Technical Graphics Communication

Important Terms of Toleranced 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

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.

TECH 104 – Technical Graphics Communication

Important Terms of Toleranced Parts

Week 10: Working Drawings

Allowance – the tightest fit

between two mating parts.

TECH 104 – Technical Graphics Communication

Important Terms of Toleranced Parts

(The minimum clearance or maximum interference).

Week 10: Working Drawings

Maximum Material Condition (MMC)

The condition of a part when it contains

the greatest amount of material.

TECH 104 – Technical Graphics Communication

Important Terms of Toleranced Parts

Least Material Condition (LMC)

The condition of a part when it contains

he least amount of material possible.

Week 10: Working Drawings

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)

TECH 104 – Technical Graphics Communication

Important Terms of Toleranced Parts

Week 10: Working Drawings

TECH 104 – Technical Graphics Communication

Fit Types:

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 begins with tolerancing the most important features.

TECH 104 – Technical Graphics Communication

Functional Dimensioning

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

Dimensioned

from the

left.

Dimensioned

from the

right.

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

AVOID THIS!!!

Week 10: Working Drawings

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.

TECH 104 – Technical Graphics Communication

Avoiding

Tolerance

Stack-up

Tolerance stack-up can

be eliminated by careful

consideration and

placement of dimensions.

(Dimension from same side).

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.

Today’s Lecture - Week 10:

Working Drawings

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

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

Assembly Drawing of a Piston & Rod containing 8 parts.

Multiview Sectioned Assembly

Drawing of a Spring Pack containing…

Drawing Number

Part Numbers

Sectioned Assembly

TECH 104 – Technical Graphics Communication

Pictorial Assemblies

TECH 104 – Technical Graphics Communication

Technical Illustration (Exploded) Assembly

Pictorial Assemblies

TECH 104 – Technical Graphics Communication

…contain...

• Name & Address of Company
• Title of the Drawing
• Drawing Number
• Names and dates of drafters,
• checker, issue date ,
• contract number, etc.
• E. Design Approval
• G. Drawing Scale
• H. Federal Supply Code for
• Manufacturers
• J. Drawing Sheet Size
• K. Actual or estimated weight
• L. Sheet Number

Title Blocks

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

Record any changes -

Found in upper-right corner

Revision Blocks

TECH 104 – Technical Graphics Communication

General tolerance note for inch and millimeter dimensions

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)
• 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

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

The difference between a finished and

Unfinished hex head bolt is a washer

Under the head of the finished bolt.

Finished vs.

Unfinished Bolts:

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

Shoulder Screw:

Check Appendix 33 for the dimensions of the shoulder screw

required for this week’s assembly drawing

TECH 104 – TechnicalGraphics Communication

This

Week’s

Drawing

Create a complete set

of Working Drawings

### TECH 104 – Technical Graphics Communication

Week 11:

Pictorial Drawings