SPM Lukisan Kejuruteraan flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Perpendicular bisector construction

Set a compass wider than half the line, draw arcs from both endpoints above and below, then join the two arc intersections. The joining line is perpendicular to the segment and passes through its midpoint.

Dividing a line equally

Draw an auxiliary line at an angle from one endpoint, step off the required number of equal compass divisions, join the last division to the other endpoint, then draw parallel lines through each division.

Tangent from external point

Bisect the line from the external point to the circle centre, draw a semicircle on that line, and where it cuts the given circle are the two tangent points. Join them to the external point.

First-angle projection layout

The object lies between the observer and the plane. The view from above is placed below the front view, and the view from the left is placed on the right of the front view.

Third-angle projection layout

The plane lies between observer and object. The top view is placed above the front view and the right-side view to its right, matching the direction from which each view is taken.

Hidden line convention

Hidden edges are drawn as short dashes of equal length separated by gaps of about one third the dash length. Dashes should meet at corners and be omitted where they clutter the view.

Isometric axis angles

The three isometric axes are separated by 120 degrees: one vertical axis plus two receding axes at 30 degrees above the horizontal. Lengths along all three axes are drawn true size.

Isometric circle ellipse axes

A circle of diameter D on an isometric face becomes an ellipse with major axis about 1.22 D and minor axis about 0.71 D; the major axis is perpendicular to the cylinder axis.

Cabinet oblique scale

In cabinet oblique the receding axis is drawn at half scale (0.5) while the front face parallel to the picture plane stays true shape; cavalier oblique uses full scale on the receding axis.

Hatching in section views

Cut material is shown by thin continuous lines at 45 degrees, evenly spaced. Adjacent components in an assembly are hatched in opposite directions or with different spacing to separate them.

Parts not sectioned lengthwise

Shafts, bolts, nuts, rivets, pins, keys and ribs or webs cut along their length are drawn unsectioned. Sectioning them would falsely suggest solid material where there is none.

Half section purpose

A half section cuts a symmetrical object halfway, showing one half in section and the other half in outside view. It reveals internal and external form in a single view without hidden lines.

Extension line clearance

Extension lines begin about 1 mm from the outline and run 2-3 mm past the dimension line. They are thin continuous lines and must not touch the object outline or cross dimension lines.

Tolerance definition

Tolerance is the permitted difference between the maximum and minimum limits of size. It equals the upper deviation minus the lower deviation and is always a positive quantity.

Hole basis fit system

In the hole basis system the hole lower deviation is zero (H). The required clearance or interference is obtained by varying the shaft letter, for example H7/g6 for a sliding fit.

Surface roughness Ra

Ra is the arithmetic mean deviation of the assessed profile from its mean line, expressed in micrometres. It is written above the tick of the surface texture symbol.

Metric thread designation

An ISO metric thread is designated M followed by nominal diameter; coarse pitch is omitted, so M10 means 10 mm diameter with 1.5 mm coarse pitch, while M10 x 1.25 is fine.

Thread root line convention

The thread crest is a thick continuous line and the root a thin continuous line drawn at about 0.85 of the major diameter. In end view the root appears as a thin three-quarter circle.

Balloon and parts list

Each component in an assembly is identified by a leader line ending in a balloon carrying the item number. The parts list gives item, description, quantity and material for each number.

Gear module formula

The module m equals pitch circle diameter divided by number of teeth (m = d / z). Meshing gears must share the same module, and the addendum equals one module.

Model space versus paper space

Model space contains the geometry at full size. Paper space holds the sheet layout, title block and viewports, where each viewport is set to the required plot scale.

CAD block behaviour

A block is a named definition inserted by reference. Re-editing the definition updates all insertions at once, whereas an exploded insertion becomes independent geometry and loses the link.

Object snap purpose

Object snaps lock the cursor to exact geometric points such as endpoint, midpoint, centre, intersection, perpendicular and tangent, ensuring lines meet precisely instead of being placed by eye.

DXF file format

DXF is a tagged, text-based exchange format that carries geometry, layers and blocks between different CAD systems. It is widely used to transfer drawings for editing elsewhere.

A-series sheet sizes

A0 measures 841 x 1189 mm and has an area of one square metre. Each smaller size halves the previous longer side, giving A1 594 x 841 and A4 210 x 297 mm.

ISO 128 line groups

Thick continuous lines show visible outlines, thin continuous lines show dimensions and hatching, dashed lines show hidden edges, and chain lines show centre lines and cutting planes.

Title block content

The title block in the bottom right corner records drawing number, title, scale, projection symbol, material, date, drawn and checked by, and the current revision status.

Projection symbol reading

The truncated-cone symbol shows the side view of a cone. In first-angle projection the small circle appears on the left of the trapezium; in third-angle it appears on the right.

Drawing sheet filing margin

A filing margin of 20 mm is left on the left edge of the sheet for binding, with 10 mm margins on the other three edges for A4 to A0 sizes under ISO 5457.

Geometrical tolerance frame

The frame is a rectangle divided into cells holding the characteristic symbol, the tolerance value in millimetres, and the datum letter where a datum is required by the control.

Drawing revision control

A controlled drawing carries a revision block recording each change with description, date and initials. Superseded copies are withdrawn so only the current issue is used.

Drawing office cutting safety

Cut on a cutting mat with a steel rule and a sharp blade, guiding the blade away from the body and keeping fingers behind the rule. Sheathe blades when not in use.