Chapter 3 - Technical Drawings Flashcards
1
Q
How does the ability to read and interpret technical drawings benefit a millwright?
A
- they are needed to understand how a machine is crafted, assembled, and installed.
- allows isolation of a problem area before a system is dismantled
2
Q
List the types of technical drawings used in industry today.
A
- orthographic drawings
— first-angle
— third-angle - pictorial drawings
— isometric
— oblique - schematic diagrams
3
Q
In an orthographic drawing, what direction is the object viewed from in the front elevation and the plan view?
A
- front elevation, the object is viewed from the front
- plan view, the object is viewed from the top or bottom
4
Q
Most often, where do first-angle projection and third-angle projection originate?
A
- first-angle projection is used in Europe
- third-angle projections is used in North America
5
Q
Describe how first-angle projection differs from third-angle projection.
A
- first-angle
— viewing position > object > side elevation - third-angle
— viewing position > side elevation > object
6
Q
Name the views that are usually required in a third-angle orthographic projection drawing.
A
- top (plan)
- front (front elevation)
- side (side elevation)
- sometime auxiliary and sectional views are needed
7
Q
Which view is chosen to be the front view for a technical drawing?
A
- most objects do not have a natural front or side position.
- therefore, it is necessary to determine which side of the object provides the most information about its shape
- this side is used as the front view
8
Q
What are the merits and limitations of pictorial drawings?
A
Merits
- 3D renderings of an object showing height, length and width
- help viewer to visualize the true shape of an object
Limitations
- do not describe the shape of an object either exactly or completely
9
Q
Describe how isometric and oblique drawings are drawn.
A
Isometric
- all lines are drawn either vertically or at 30 degrees to the horizontal
- the lengths along the 30 degrees axes are drawn to full scale
Oblique
- on face is at right angle to the horizontal and the others are at an angle (usually 45 degrees) to the horizontal
- the receding dimensions along the 45 degrees axis are drawn to half scale
10
Q
How is line thickness defined by Canadian standards?
A
- Canadians standards define line thickness as THICK or THIN
- thick lines - twice as thick as thin lines
11
Q
Draw and describe
- construction lines
A
- thin lines used to lay out the various views of an object
- construction lines are eventually overpaid by the object lines
12
Q
Draw and describe
- object lines
A
- thick lines which indicate the visible outline of an object
13
Q
Draw and describe
- hidden lines
A
- show those surfaces and features of the object that are not seen in the chosen views
- they are thin, equally spaced, broken lines
14
Q
Draw and describe
- break lines
A
- used to shorten the view of long uniform sections
15
Q
Draw and describe
- section lines
A
- the parallel diagonal lines (hatch marks) that identify a sectional view of an object in a drawing
16
Q
Draw and describe
- centrelines
A
- drawn as thin, broken lines, with long and short lines spaced alternately
17
Q
Draw and describe
- cutting plane line
A
- offset cutting plane lines are usually if the broken type
- letters placed beside arrows key to the corresponding sectional view
18
Q
Draw and describe
- extension and dimension lines
A
- Extension lines
— thin lines which extend the object lines out to a convenient space for dimensioning
— these lines do not touch the object lines
— if extension lines cross arrowheads or dimension lines, a break in the extension line is permitted - Dimension lines
— thin lines which indicate the distance between the extension lines. They terminate with arrowheads which touch the extension lines.
— these lines give the objects measured dimensions; height, width and length
— where one or more dimension lines share an extension line, the dimension lines should run parallel to each other
19
Q
What are the two methods used to dimension objects?
A
- Aligned method
— all dimension figures except angular dimensions are written parallel to the dimension lines - Unidirectional dimensioning
— all figures are written parallel to the bottom of the drafting paper
20
Q
What two types of dimensions are found on technical drawings?
A
- Overall dimensions
— indicate overall length, width, or height of an object - Detail dimensions
— give size and location of any feature or detail which is not overall length, height or width
21
Q
State the rules for dimensioning technical drawings
A
- only one form of dimension is used on a single drawing; either aligned or unidirectional
- technical drawings are dimensioned so that the full-size dimensions are specified on he drawing regardless of scale
- in metric drawings, dimensions are shown in millimetres without their units (1100, not 1100mm)
- the position and size of angles are shown
- when metric values are less than one, a zero is shown before the decimal point (0.5, not .5)
- whenever possible, to avoid confusion, dimensions are placed close to features being shown and outside the objects outline
- dimensions of a feature are shown only once
- when space is limited, dimension figures are placed in one or the other way
— inside the dimension line with the arrowheads outside the extension lines
— with the figures and arrowheads outside the extension lines
22
Q
What are the overall dimensions of the object in figure 11?
A
-
23
Q
What is the hole size and the size and depth of the counter-bored hole in figure 13?
A
-
24
Q
Where are the holes located in the square plate in figure 14?
A
-
25
What is the diameter of the bolt pattern in figure 15?
-
26
What are the purposes of sectional view?
- used to show an aspect of the object which is otherwise too complicated to show with the conventional top, front, and side views
- show differences in materials
27
Describe the difference between full-section and half-section views.
Full section - use a cutting plane through the whole object giving the impression that the object has been cut in half
Half section - remove only a certain portion of the drawing. If a half section views gives all the information needed to understand the drawing, hen a full section drawing is not given
28
Which views are pictorial and which views are orthographic in figure 16?
-
29
Can section lines identify the material and object is made from?
- line patterns are used to indicate types of materials
| - also indicate solid portions of an object
30
How are offset sectional cutting planes indicated on the drawing in figure 18?
-
31
Where is the lower bolt hole located in the aligned sectional view in figure 19?
-
32
How are holes illustrated in a sectional view when the cutting plane line passes through them?
- blank dimensioned without line patterns
33
How is a removed sectional view identified? Figure 21
- sectional labelling
34
Describe how the broken-out sectional view in figure 22 helps in the understanding of the object.
- shows X-ray of interior dimensions
35
What are the reasons for using auxiliary views?
| Figure 23
- used to detail sloping (or inclining) surfaces which cannot be depicted in normally orthographic views
- clearly shows the shape of the object and gives its true dimensions
36
Which of the regular views is the front view in figure 23?
-
37
Why would and object have two or more auxiliary views?
- occasionally an object cannot be completely described in one auxiliary view, so an additional auxiliary view may be needed
38
What are the merits of the exploded view in figure 24?
- exploded views take a very complicated drawing and separates it along s common axis where possible
- the viewer sees exactly how a group of parts fit together
39
Is the exploded view orthographic or pictorial in figure 24?
-
40
Define tolerance.
- the total permissible/allowable variance of the basic size of a component
- tolerance limits are the maximum and minimum sizes that are allowable
- the tolerance is the difference between the max and min limits
41
What is the maximum and the minimum material size for the following?
- 28.00 +0 -0.06 mm
- 28.00mm
| - 27.94mm
42
What is the maximum and the minimum material size for the following?
- 33.00 +0.08 - 0 mm
- 33.00mm
| - 33.08mm
43
What is the maximum and the minimum material size for the following?
- 42.50 +- 0.5 mm
- 42.00mm
| - 43.00mm
44
What is the advantage of the direct method of indicating tolerance?
- shows both upper and lower limit together
- eliminates any calculations concerning maximum and minimum tolerances
- not the upper and lower limits are given, and the MMC is given in the upper position
45
Draw and ISO datum-feature symbol
- [A]-
46
What is the significance of a datum or reference point?
- when several tolerances are given in a sequence, a datum or reference point should be given
- all dimensions are referenced to this point
47
What is the maximum tolerable overall length of the part featured in figure 26?
-
48
Define clearance and interference fits.
- tolerances May be either clearance (positive), or interference (negative) fit
Clearance - one in which the machines pieces can be fitted by hand
Interference - requires heat, cold, or a combination of both to assemble the piece
49
Draw symbols to indicate the following:
| - part must be straight within 0.10mm
- — 0.10
50
Draw symbols to indicate the following:
| - shaft runout must be within 0.8 mm
-↗️🅰️🅱️0.8
51
State the primary measurements for surface texture
- micrometer (um) — a micrometer is one millionth of a metre (0.000 001 meters)
- micro-inch (uin) — a micro-inch is one millionth of an inch 0.000 001 inch)
52
What would be a typical application for a drilled hole with a finish between N8 and N7?
Table 1
- good for close fits
| - unsuitable for fast rotating members
53
List the information blocks used on technical drawings to relay information.
- zone numbers
- title block
- revision block
- materials list
- scale
54
What is the purpose of zone numbers and letters?
- refer to certain areas on the print in much the same fashion as coordinate numbers on a map
55
Where is the title block located on a technical drawing and what information does it contain?
- should always appear in the lower right-side of the printed
- contains information as the — drawing number, title or description of the part, the name of the firm that prepared the drawing, and the scale, as well as any other provisions made
56
Where is a revision block located and what information does it contain?
- may be placed either in the lower left- or upper right-hand sides of the print
- lists any and all revisions made to the drawing after the initial drafting of the print
57
What revision was made on Feb.24/96 by G. Burns to the drawing in figure 34?
-chamfer added
58
Where is the materials list located on the technical drawing and what does it contain?
- generally located just above the title block
- if there is no revision black in the upper right-hand, then the material list is placed here
- May also be called the item list
- all parts in a materials list are identified by their part or stock number
- provides for the number and size of each of part including all fasteners, such as bolts, washers and nuts
59
How long will the drawing of a part be if the part is 980mm long and it is drawn to a scale of 1:5?
- 5X smaller than actual size
| - 196mm
60
What information does a detail drawing contain?
- a description of the shape
- all necessary views and lines needed to describe the complete form of the object
- all dimensions and numerals including tolerances used to specify the object
- general notes, including such thing s ax the materials list, any heat treating, machining, and surface texture
61
Is the drawing first-angle or third-angle projection in figure 35?
-
62
What materials are the following items made of in figure 35?:
- #1 the hook?
- steel
63
What materials are the following items made of in figure 35?:
- #5 the bushing?
- bronze
64
What materials are the following items made of in figure 35?:
- #8 the locking pin?
- steel
65
What is the measurement between centres of the hook and the clevis pin in figure 35?
-
66
What size is the throat opening in the hook in figure 35?
-
67
What information does and assembly drawing contain?
- an assembly drawing shows the various pieces of a machine and the way they fit together as a complete unit
- used to show the correct working relationship of the mating pieces and their functions
68
What information does schematic diagrams communicate to the reader?
- facilitates he tracing of hydraulic, pneumatic, or electrical lines and components of each
- shows relationship between various parts of a system
- shows connections, functions and flows
69
What information is not communicated to the reader of schematic diagrams?
- does not show the actual size, shape, or location of the components or devices within the system
70
What is the pressure for the hydraulic system in figure 36?
-600 PSI
71
What information is communicated to the reader of pipe drawings?
- shows functions, connections, flow, and spatial location
72
Which views are the plan view, the elevation view and the side view in figure 39b?
-
73
Compare single-line to double-line pipe drawings.
- single line — abstract symbols
| - double line — pictorial schematic
74
What institutions publish symbols for welding, piping, surface texture, and electrical elements?
- ISO — international standards organization
- CSA — Canadian standards association
- ANSI — American national standards institute
