Mechanical Drawing - Paper 2 Flashcards
What type of line is shown in the image?
Continuous thick outline, dark pencil, 0,3-0,5
What type of line is shown in the image?
Continous medium line; medium pencil; 0,15
What type of line is shown in the image?
Continuous thin construction line, light pencil; 0,09
What type of line is shown in the image?
Hidden detail; medium pencil; 0,15
What type of line is shown in the image?
Centre line; medium pencil; 0,15
What type of line is shown in the image?
Cutting plane; medium chain with dark ends; 0,15 or 0,4
What type of line is shown in the image?
Short break or part section line; medium pencil; 0,15
How should mechanical drawings be presented?
In third-angle orthographic projection
What should be included on the drawing with engineering drawings?
It is common practice to include a projection symbol on the drawing.
Where should the projection symbol be placed on an engineering drawing?
The projection symbol should always be placed below the drawing.
What is the rule on linework for centrelines in circles?
The lines extend only a short distance beyond the feature.
What is the rule on linework for hidden detail lines?
The dashes are always slightly longer than the spaces.
What is the rule on linework for centre lines in rectangles?
The long lines always cut the profile of a feature.
What is the rule on linework for hidden detail lines in terms of outlines?
Hidden detail lines start and end in contact with outlines.
What is the rule on linework for centre lines when there are multiple views on one page?
Views are never joined by a centre line.
Should hidden detail lines meet at intersections?
Yes, hidden detail lines meet at intersections.
What are the surface texture of machined components made up of?
Hills and valleys.
How is the roughness of a surface measured?
By taking the average arithmetic deviation of the hills and valleys over a given length.
Why is the surface finish on load-bearing and high speed components very important?
To reduce friction for the correct functioning of the component.
What information is needed when a surface has to be machined to certain specifications?
The roughness, treatment and lay of the surface is needed.
What information does this symbol give you?
The roughness, treatment and lay the surface needs after machining.
What does the machining and surface texture symbol look like?
The basic symbol consists of 2 legs of unequal length inclined at 60 degrees to the horizontal.
When is a horizontal bar added to the longer of the two legs of the machining and texture symbol?
A horizontal bar is added if more than a removal of material is required.
What information needs to be added to the machining and surface texture symbol in order for it to have meaning?
Values defining the surface texture and production surface.
What information is added to the machining symbol in position a?
Roughness value or roughness grade number
What information is added to the machining symbol in position b?
Method: treatment or coating
What information is added to the machining symbol in position c?
Sample length
What information is added to the machining symbol in position d?
Direction of lay
What information is added to the machining symbol in position e?
Machining allowance
What information is added to the machining symbol in position f?
Other roughness value
What is the roughness value (a) given in?
Either in microns or shown by a grade number which represents the roughness value of the surface. Sometimes the value is displayed with an upper and a lower limit.
List 6 treatments of methods that could be listed as (b) on a machining symbol?
Chemical; honing; grinding; machining; lapping; plating; turning.
Why is value (c) needed on a machining symbol?
Sometimes it is necessary to specify a length over which the finish will be measured.
What is the direction of the lay?
The direction of the lay (d) is the direction of the predominant surface pattern, normally determined by the method used to produce the surface finish.
What direction of lay is indicated by this symbol?
Parallel to the plane
What direction of lay is indicated by this symbol?
Multi directional
What direction of lay is indicated by this symbol?
Circular pattern
What direction of lay is indicated by this symbol?
Crossed pattern
What direction of lay is indicated by this symbol?
Radial pattern
What direction of lay is indicated by this symbol?
Perpendicular to plane
How is machining allowance (e) expressed?
It is expressed in mm and is a degree of permissible variance over a specified distance.
How would a machinist read this symbol?
The indicated surface must be finished by machining to a roundness value of 0,8 microns, machined perpendicular to the plane of projection, with a machining allowance of 0,2mm. The roughness of the surface must be measured over a sample length of 4,5 mm.
What do the numbers in this symbol indicate?
The upper and lower roughness value.
Where should the machining symbol be placed on a drawing?
Both the symbol and the inscriptions should be orientated so that they can be read from either the bottom or the right-hand side of the drawing sheet.
How do you avoid the repetition of a symbol when the same machine process and values must be applied to all the surfaces of the component?
Only one symbol should be placed near the drawing
How do you avoid repetition of complicated symbols on a drawing?
Use a reference system that links all surfaces that require the same finish to a single symbol.
What is welding?
Welding is a process that joins metals together by fusing the surfaces of the parts into a single homogenous mass, and the bond can be regarded as permanent.
Which industries make use of welding?
Engineering and manufacturing industries.
How are welds specified on drawings?
A complex symbol describing the weld, its size and length with other processing and finishing information is used.
List 3 types of welding processes.
Gas welding
Arc welding
Resistance welding
Which factors determine which welding process should be used?
The thickness of the metal and the required strength of the join.
List 5 types of welded joints.
Corner joint; butt joint; T joint; lap joint; edge joint
What type of weld joint in shown in the image?
Corner joint
What type of weld joint in shown in the image?
Butt joint
What type of weld joint in shown in the image?
T joint
What type of weld joint in shown in the image?
Lap joint
What type of weld joint in shown in the image?
Edge joint
What does the basic welding symbol consist of?
It consists of an arrow which points at the join and a horizontal reference line. The weld symbol is added to the reference line showing that a weld is required along the joint at the arrow point.
Where should you place the welding symbol if you want the join welded on the same side as the arrow?
The symbol is place below the reference line.
Where should you place the welding symbol if you want the join welded on the opposite side as the arrow?
The symbol is place above the reference line.
List 5 types of welds.
Surface; fillet; groove; plug and slot; square; bead; bevel; single V; single J; single U.
What factors would determine which type of weld should be used on a join?
The relative placement of objects to each other; the required strength of the join; the thickness of the plates and the composition of the material.
What type of weld is shown in the image?
Fillet weld
What type of weld is shown in the image?
Square weld
What type of weld is shown in the image?
Bevel V weld
What type of weld is shown in the image?
Plug of slot weld
What type of weld is shown in the image?
Bead weld
What type of weld is represented by the sectional view and symbol shown in the image?
Square weld
What type of weld is represented by the sectional view and symbol shown in the image?
Bead weld
What type of weld is represented by the sectional view and symbol shown in the image?
Bevel weld
What type of weld is represented by the sectional view and symbol shown in the image?
Single V weld
What type of weld is represented by the sectional view and symbol shown in the image?
Single J weld
What type of weld is represented by the sectional view and symbol shown in the image?
Single U weld
What type of weld is represented by the sectional view and symbol shown in the image?
Plug or slot weld
What type of weld is represented by the sectional view and symbol shown in the image?
Fillet weld
How do you indicate that the weld must extend all the way around the join in a drawing?
It is indicated on the welding symbol by placing a circle on the join where the arrow line meets the reference line.
What is a field weld?
There are occasions when a join cannot be welded during the manufacturing process in the factory and has to be welded on site, or in the ‘field’.
How do you indicate that a weld needs to be made in the field instead of during manufacturing?
This is indicated on the welding symbol by placing a solid circle on the join where the arrow line meets the reference line.
What is the pitch of a weld?
The length and spacing of a weld.
How is the pitch of a weld measured?
It is always measured from the centre of one weld to the centre of the next weld.
Where do you indicate the pitch of a weld on a welding symbol?
On the reference line to the right of the welding symbol.
Study this image carefully so you know how to take the various measurements in the exam.
How long are the legs of a fillet weld usually?
The legs of a fillet weld are usually the same length.
Where should the length of the leg of a fillet weld be indicated on a drawing?
The dimension showing the length of the legs is indicated on the reference line, always to the left of the weld symbol.
What should you do when the length of the legs of a fillet weld need to be different form each other?
You indicate both of the leg lengths in brackets.
When do you add a tail to the end of the reference line on a welding symbol?
Only when a specified welding process needs to be carried out. If the tail is not needed it should be left off the symbol.
What does this resistance weld symbol indicate?
Spot resistance
What does this resistance weld symbol indicate?
Seam resistance
What does this resistance weld symbol indicate?
Flash or upset resistance
List three types of contour symbols.
Flush; concave; convex
What are contour symbols also known as?
Weld surface finishes.
Which type of contour symbols is shown in the image?
Flush contour
Which type of contour symbols is shown in the image?
Concave contour
Which type of contour symbols is shown in the image?
Convex contour
What should accompany the contour symbol?
The intended method of achieving the required finish.
How do you indicate the required method for achieving a finished surface on a contour symbol?
The designated letter is placed above the contour symbol.
Which finishing method is indicated by an M on a contour symbol?
M = Machine
Which finishing method is indicated by an F on a contour symbol?
F = Flame
Which finishing method is indicated by a C on a contour symbol?
C = Chisel
Which finishing method is indicated by a G on a contour symbol?
G = Grinder
Which finishing method is indicated by an R on a contour symbol?
R = Rolling
Which finishing method is indicated by an H on a contour symbol?
H = Hammer
What needs to be specified when a groove weld is used?
The angle of the groove needs to be specified.
How do you specify the angle of the groove on a drawing?
The angle of the groove is placed on top of the weld symbol.
When do you add the depth of penetration to a weld symbol?
When the weld does not go through the material but only penetrates the material.
Where do you indicate the depth of penetration on a weld symbol?
Just above the weld symbol
What information should a welding symbol contain?
It should only contain the information that is needed to complete that specific weld, all the other information should be left off.
What is the symbol in the image?
A complete welding symbol showing the position of all the information.
Which element of a weld symbol is indicated at arrow 1?
Finish symbol
Which element of a weld symbol is indicated at arrow 2?
Contour symbol
Which element of a weld symbol is indicated at arrow 3?
Groove angle; included angle of countersunk for plug welds
Which element of a weld symbol is indicated at arrow 4?
Root opening; depth of filling for plug and slot welds
Which element of a weld symbol is indicated at arrow 5?
Size or strength; for certain welds
Which element of a weld symbol is indicated at arrow 6?
Tail: may be omitted when reference is not used.
Which element of a weld symbol is indicated at arrow 7?
Welding process
Which element of a weld symbol is indicated at arrow 8?
Basic weld symbol
Which element of a weld symbol is indicated at arrow 9?
Number of spots or projection welds
Which element of a weld symbol is indicated at arrow 10?
Arrow side of weld
Which element of a weld symbol is indicated at arrow 11?
Arrow line
Which element of a weld symbol is indicated at arrow 12?
Field weld
Which element of a weld symbol is indicated at arrow 13?
Weld-all-round
Which element of a weld symbol is indicated at arrow 14?
Centre-to-centre spacing of weld
Which element of a weld symbol is indicated at arrow 15?
Length of weld
Which element of a weld symbol is indicated at arrow 16?
Reference line
Which element of a weld symbol is indicated at arrow 17?
Other side of weld
What is nominal size?
The designation which is used for identification purposes (dimension).
What is basic size?
The size from which limits of size are derived by the application of allowances and tolerances.
What is deviation?
The algebraic difference between the limits of size and the corresponding basic size.
What is a zero line?
This is the line of zero deviation and represents the basic size reflected on a drawing without a tolerance.
What are limits?
The maximum and minimum sizes as indicated by a tolerance dimension.
What is an allowance?
The minimum clearance space between the material of mating parts or the tightest permissible fit.
What are manufacturing errors?
Errors that occur during the manufacturing process.
List 3 kinds of manufacturing errors.
Error of size; error of form; error of position.
What is the purpose of a tolerance?
A tolerance is intended to allow for managed inaccuracy and is defined as the total amount of a specific dimension that is permitted to vary between a maximum and minimum limit, if the component or assembly is to function as planned.
Define the term ‘fit’.
Fit is the general term used to signify the range or tightness or looseness which may result from the application of a specific combination of allowances and tolerances in mating parts.
What factors does a particular fit depend on?
A particular fit will depend solely on the prescribed maximum and minimum limits of size of the two components which are assembled.
List the 3 main types of fit in engineering.
Clearance fit; interference fit; transition fit
What is a clearance fit?
This is a fit where the shaft is always smaller than the hole into which it fits.
Which applications are typical for a clearance fit?
Rotating shafts; fast and loose pulleys; bearings and similar components.
What is an interference fit?
This is a fit where the shaft is always bigger than the hole it fits into.
Which applications are typical for an interference fit?
Press-in bushes or sleeves, crank pins and shrunk on couplings.
What is a transition fit?
This is a fit which provides either a clearance or an interference, meaning the shaft may be bigger or smaller or the same size as the hole it fits into.
Which applications are typical for a transition fit?
Bushes; spigots; fasteners; pins; keys and components used for locating purposes.
How do you indicate tolerances on a drawing?
On a drawing, tolerances of size are indicated by the maximum and minimum permitted sizes, which are called the limits of size.
Why are tolerances important?
To ensure that an assembly of mating components will function correctly the designer must ensure that all the parts fit together in the required manner.
What does the ISO system of limits and fits provide?
It provides a comprehensive range of tolerances, limits and fits for engineering purposes as well as fundamental deviations for holes and shafts, by specifying the position of the tolerance zone.
What does the ISO system of limits and fits consist of?
The system consists of a set of letters and values associated with each designation.
What do the complete designation of the limits and size for a shaft or a hole consist of?
The appropriate letter indicating the fundamental deviation and a suffix number indicating the tolerance grade.
List two types of fit systems the ISO system provides.
Shaft-basis system
Hole-basis system
How does the shaft-basis system work?
The diameter of the shaft is used as a constant and the size of the hole varies to fit the shaft.
How does the hole-basis system work?
It requires that the hole remains constant while the size of the shaft is altered to fit the hole.
Which system is preferred? The shaft-basis system or the hole-basis system?
The hole-basis system is preferred because it is more economical.
What measurement is used for the nominal size?
mm - millimetres
What measurement are the upper and lower deviations of the nominal size expressed in?
Micrometers
Why must ISO values be expressed in mm on a drawing?
Because all dimensions are expressed in mm on engineering drawings.
What is shown in this image?
The image indicates a tolerance on linear dimension.
What does this image show?
The diagram shows a datum surface from which the dimensions for positioning a series of holes should be taken to avoid multiple errors.
What does the method of locating a hole from two surfaces at right angles to each other result in?
The centre of the hole could lie anywhere within a square tolerance zone due to the tolerance of each dimension.
What is shown in this image?
Two methods of constructing the chamfer on a hexagonal fastener.
What does this image show?
Calculating sizes using M
What is shown in this image?
A blind tapped hole
List 3 types of nuts.
Lock nut; castle nut; self-locking nut
What type of nut is shown in this image?
A lock nut
What type of nut is shown in this image?
A castel nut
What type of nut is shown in this image?
A self-locking nut
What is a cutting plane in mechanical drawing?
It is an imaginary plane that passes through an object at a given place.
How is a cutting plane indicated in mechanical drawing?
It’s indicated by a thickened line on either end. An arrow is placed on either thickened end of the line indicating the direction from which the cut surface is viewed.
List 2 types of sections.
Full-section; half-section
What is a full section?
When a cutting plane passes through a single component or an assembly as one continuous plane, the part of the object that prevents the observer from seeing the cut surface is removed. The entire surface that is left behind is then sectioned.
What is a half-section?
A half section requires that one half of the view is shown as an outside view while the other half is shown in section.
When can a component or an assembly be represented as a half-section?
When a component or an assembly is symmetrical the section can be presented as a half-section.
What rule applies when you are sectioning components that are too thin for hatching?
They may be filled in solid with a space left between adjacent parts.
When is a revolved section used?
It is used to show the true shape of a cross section on the view of a component.
What is a revolved section?
A section that is drawn by revolving the cutting plane in position to show the true shape of a cross-section.
What is a removed section used for?
To show the true shape of a cross section of a component.
Where do you place a removed section on a drawing?
The section may be placed near the view or connected to the view by the lines of symmetry through the cutting plane.
What type of section is shown in this image?
A revolving section
What type of section is shown in this image?
A removed section
What type of section is shown in this image?
An aligned section
What type of section is shown in this image?
An offset section
What is an aligned section?
In order to include angled elements in a sectioned view the cutting plane may be bent to pass through these features.
How is an aligned section created?
The cutting plane and the feature are first straightened or aligned, by rotating them into a single plane, before the feature is projected to the sectioned view.
What do you do to indicate the bent sections of the cutting plane on an aligned section drawing?
Wherever the cutting plane is bent, these parts of the plane are thickened.
When do you use an offset- section?
When cutting through irregular shaped objects it is often desirable to show the cutting plane passing through several features that do not lie in a straight line.
How is an offset section achieved?
This can be achieved by offsetting or bending the cutting plane. The offsets, or bends, in the cutting plane must be drawn at 90 degrees to each other and are not shown in the sectional view.
What type of section is shown in this image?
Succesive sections
What is the purpose of successive sections?
Successive sections show the true shape of a number of sections through a single component.
How should the sections be placed in successive sections?
The sections should be placed in line with the direction indicated by the arrows, but when space is limited, the sections may be placed as shown in the diagram.
What type of view is shown in this image?
An auxiliary view of a component.
When is an auxiliary view projected?
Components with an inclined part or face may have an auxiliary view projected to show the true shape of the inclined part, with the direction of view shown by an arrow.
Where should an auxiliary view be drawn?
Wherever possible, a view of an inclined face should be drawn in line with the direction of the arrow.
List the parts that are not sectioned when a cutting plane passes through them longitudinally.
Ribs and webs; nuts, bolts and thin washers; shafts, rods and spindles; keys, pins and cotters; rivets, spokes of wheels and similar parts.
What is a conventional representation?
Conventional representations are standardised drawings that are used to save time and space when a commonly occurring feature is being drawn.
In what form should conventional representations be represented?
In simplified or conventional form.
Where can you find the conventional form of commonly used objects?
The SANS 10111
Which feature is shown in this detailed representation?
An interrupted view
Which feature is shown in this detailed representation?
Repeated features
Which feature is shown in this detailed representation?
Holes on a linear pitch and circular pitch.
Which feature is shown in this detailed representation?
Square on a shaft
Which feature is shown in this detailed representation?
Knurling
Which feature is shown in this detailed representation?
Cylindrical helical compression spring.
Which feature is shown in this detailed representation?
Bearings
Which feature is shown in this conventional representation?
An interrupted view
Which feature is shown in this conventional representation?
Repeated features
Which feature is shown in this conventional representation?
Holes on a linear pitch and circular pitch.
Which feature is shown in this conventional representation?
Square on a shaft
Which feature is shown in this conventional representation?
Knurling
Which feature is shown in this conventional representation?
Cylindrical helical compression spring
Which feature is shown in this conventional representation?
Bearings
Which feature is shown in this detailed/conventional representation?
Partial view of symmetrical components.
Which feature is shown in this detailed/conventional representation?
Enlarged auxiliary partial view.
Name 2 types of dimensions.
Location dimensions and size dimensions.
What are location dimensions?
Location dimensions define the relationship of features to an object by specifying the relative positions of the various features to one another.
What are size dimensions?
Size dimensions are placed directly on a feature to identify size or may be connected to a feature in the form of a note.
What is a note?
A note is a type of dimension that identifies the zone of a feature with more than just a numerical specification.
Name two types of notes.
Local notes and general notes.
What are local notes?
Local notes are connected to specific features of a drawing.
What are general notes?
General notes are placed separate from views and relate to similar features on the entire drawing.
What is the problem with dimensions?
They take up a lot of space on a view and the difficulty with dimensioning is determining the space requirements before any drawing takes place or during the planning stage.
Where should the leaders be placed when establishing notes for holes?
The shoulder of the leader should be centred upon the beginning of the note when the note goes out to the right, and the end of the note when the note goes out to the left. The arrow on the leader must join with the centre of the hole being dimensioned.
What do aligned dimensions require?
That all the numbers, figures and notes be aligned with the dimension line, so that they may be read from the bottom or the right side of the drawing sheet.
What is datum dimensioning?
A common method of dimensioning machine parts whereby each feature is dimensioned from a common surface, axis or centre plane.
Are dimensions in datum dimensioning dependent?
No, they are independent so there is no tolerance buildup.
Which 3 dimensions require notes?
Counterbore; spot face and countersunk hole.
What is a counterbore?
A hole machined below the surface of a part and is used for concealing a bolt head or fastener.
What is a spotface?
A shallow or a raised machined surface used for seating a washer or fastener.
What is a countersunk hole?
A tapered hole machined into the surface of a part and is used to recess the head of a shaped fastener below the surface.
Give examples of dimensions that require an abbreviation or a combination of numbers to describe the feature fully.
A sphere, a chamfer and an angle
Does this image show correct or incorrect dimensions?
Correct dimensioning.
Does this image show correct or incorrect dimensioning?
Incorrect dimensioning
What does AF mean?
Across flats
What does ASSY mean?
Assembly.
What does CL mean?
Centre line.
What does CRS mean?
Centres.
What does CHAM mean?
Chamfer.
What does CSK mean?
Countersunk
What does CBORE mean?
Counterbore
What does ° mean?
Degree
What does ∅ mean?
Diameter
What does DRG mean?
Drawing
What does EQUI SP mean?
Equally spaced
What does INSUL mean?
Insulation
What does ISO mean?
International Organisation for Standardisation
What does LH mean?
Left hand
What does MCD mean?
Machined
What does MAX mean?
Maximum
What does M mean?
Metric thread
What does MIN mean?
Minimum
What does NTS mean?
Not To Scale
What does PCD mean?
Pitch circle diameter.
What does R mean?
Radius
What does RH mean?
Right hand
What does SPEC mean?
Specification
What does SPH mean?
Sphere
What does SFACE mean?
Spotface.
What does SI mean?
Systeme International
What does TOL mean?
Tolerance
What is an assembly drawing?
It is used to show how various components or parts that make up a product fit together and includes information such as dimensions and labels.
What is a detail drawing?
A drawing of a single component or part that is usually drawn to a larger scale and used for manufacturing purposes.
What information is included in a detail drawing?
Dimensions, labels, codes, standards, materials, treatment requirements, surface texture and tolerances.
