Welding General

7/28/2019 Welding General

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Engineering H191 - Drafting / CAD

Gateway Engineering Education Coalition Lect 22 P. 1Autumn Quarter

Fasteners and Welding

Lecture 22


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Whats Coming Up?

Today

Fasteners & Welding

Tuesday

Working Drawing Set

Wednesday

Measurements Lab

Thursday Quiz on Fasteners and Welding

Introduction to AutoDesk Inventor


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Fasteners and Welding

Objectives:

Understand importance of fasteners, learn how

to specify threaded fasteners and represent

them in drawings and learn about otherfastening methods.

Understand basics of welding symbols


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Topics For Today

Importance of fastening

Threaded fasteners

Non-threaded fasteners

Other machine elements

Adhesives

Welding


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Importance of Fastening

50% of production time for the average item is

spent on assembly/fastening.

Fasteners are critical to product performance and

reliability Choosing the proper fasteners is an important

part of product design


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Three Methods Commonly Used in

Fastening Mechanical Fastening

Bolts, screws, rivets, keys, pins

Paper clips, zippers, Velcro

Bonding

Welding, soldering, brazing, gluing

Forming

Sheet metal, plastic snaps parts


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Threaded Fasteners Terminology

External Threads


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Internal threads

Threads inside a hole

Made by drill & tap:

drill smooth hole

make threads with a tap


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Bolt - head on one end, threads on other end,

used with a nut

Stud - rod threaded at both ends

Cap screw - head on one end, threads on otherend, NOT used with a nut

Machine screw - similar to cap screw but smaller

Set screw - used to prevent 2 rotating parts from

moving separately


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Threaded Fasteners Specification

.5 - major diameter of .5 inches 28 - 28 threads per inch

UN - form Unified (i.e. shape of the thread)*

C - series (C means coarse), F (fine), EF (extra fine)

Example of a typical thread specification (in inches)

.5 - 28 UNC - 3 B

* There are several thread forms. UN is

common.


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3 - class of fit (3 is precise, 2 is normal, 1 is

loose fit)

B - internal thread (A is for external)

Continuation of example of a typical thread

specification (in inches)

.5 - 28 UNC - 3 B


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M - indicates thread form is metric

6 - major diameter in millimeters

1 - pitch in millimeters

4H5H - tolerance (capital letters for internal thread, lower case

for external thread)

Example of a typical metric thread specification

M6 x 1 - 4H5H



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Schematic2.

1.

EndView

Detailed

Representing External Threads

Options for representing external threads in a

drawing


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Representing Internal Threads

Options for representing internal threads

Schematic(in section)

Detailed(in section)

Unsectioned End View


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Non-Threaded Fasteners

Rivets

Pins

Keys

Retaining rings

Locking washers


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Other Machine Elements

Springs

Bushings

Bearings

(See references for more details)


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Adhesives

Used to join thin or dissimilar materials

Seal a joint as well as bond it

Can be used to coat threads and prevent

loosening


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Thermal Fastening

Soldering - solder (filler) melts but parts to be

joined remain at low temperature

Brazing - filler is melted, and parts to be joined

are heated but do not melt. Can be used to joindissimilar metals

Welding - parts to be joined and filler (if any) are

melted, pressed together and then cool. (See

Section 9.8 in BTG)


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Welding Symbol

Reference Line

Leader and arrow

Basic weld symbol (location & depth of weld)

Finish symbol

Weld symbol

Dimensions

Supplementary symbols Tail and specifications


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Welding Symbol

Leader

Reference Line

Tail


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Welding Symbol Example

Fillet Weld

Weld around

Arrow side

Opposite side

Specification Result


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Welding Symbol

Below reference line describes the ARROW side

of the weld

Above the line describes the OTHER side

Joint described by symbol (fillet, square)

Numbers by symbol indicate size

Circle at joint specifies weld around


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References

Threaded and Other Fasteners

BTG Chapter 9, Appendices A24 A42

Welding

BTG Appendix B.25


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Assignments

Dwg 43 FB-1D Fasteners

Answer questions about fasteners using thetables in the book.

Due Today Dwg 44 FD-3B Welding Symbology

Add notes to the Welding Symbols as neededto make them match the schematic

Due Tuesday Dwg 45 Working Drawing Set

A Handout will be provided in class

Welding General

Documents

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