MSCE Technical Drawing flashcards

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

A0 sheet area

One square metre, with sides in the ratio 1:√2 (841 × 1189 mm). Every smaller A size is obtained by halving the longer side.

T-square function

Slides along the drawing board's working edge to give horizontal reference lines; set squares are used against its blade to draw verticals and angles.

Pencil grades for drawing

H or 2H for construction and layout lines, HB or B for visible outlines and lettering, and 2B to 4B for freehand sketching.

Perpendicular bisector construction

From each end of the line, draw equal arcs of radius greater than half the line. The line joining the two intersections is perpendicular and bisects the original line.

Dividing a line equally

Draw an auxiliary line at any angle, step off n equal divisions with dividers, join the last division to the line end, and draw parallels to divide the line into n parts.

Tangent from external point

Bisect the line from the external point to the circle centre, draw a semicircle on it, and the intersections with the circle give the tangent points.

Ellipse focal property

For any point on an ellipse the sum of distances to the two foci is constant and equals the major axis. The focus offset from centre is √(a² − b²).

First-angle projection layout

The object lies between observer and plane, so the top view is placed below the front view and the left-side view is placed on the right.

Third-angle projection layout

The plane lies between observer and object, so the top view appears above the front view and the right-side view appears to the right.

Hidden detail line style

Short dashes of equal length, medium thickness. Dashes should meet at corners and not cross visible outlines; hidden lines are omitted where clarity suffers.

Shared view dimensions

Front and top views share width, front and side views share height, top and side views share depth. Views must align by projection.

Hatching angle convention

Section lines are thin continuous lines at 45° to the principal outlines. Adjacent parts in an assembly are hatched in opposite directions or at different spacings.

Parts not hatched in section

Shafts, bolts, nuts, rivets, pins, keys, webs and ribs cut longitudinally are left unhatched; so are standard parts such as bearings and gears cut lengthwise.

Half section

One quarter of the object is removed, showing half the view in section and half as an outside view. The dividing line is a centre line, not a visible edge.

Broken-out section

A local section bounded by a thin irregular freehand break line, used to expose a small internal feature without sectioning the whole part.

Isometric axis angles

The three axes are 120° apart, drawn at 30° above the horizontal on each side. Distances along the axes are drawn at full scale.

Isometric circle ellipse axes

A circle of diameter D appears as an ellipse with major axis 1.22 D and minor axis 0.71 D. The major axis is perpendicular to the cylinder axis.

Cabinet oblique projection

The front face is drawn true shape, the receding axis is at 45°, and depths are drawn at half scale to reduce distortion. Cavalier oblique uses full depth scale.

Perspective vanishing points

Lines parallel to a given direction converge at that direction's vanishing point on the horizon. One-point perspective has one such point, two-point perspective has two.

Extension line gap

Extension lines start about 1 mm from the object outline and extend about 2 mm beyond the dimension line. Dimension lines are thin continuous lines with arrowheads.

Baseline versus chain dimensioning

Baseline dimensioning measures every feature from a common datum and avoids tolerance stack-up. Chain dimensioning adds tolerances at each step and is less accurate.

Hole-basis fit system

The hole is H with lower deviation zero. Shaft letters a–h give clearance, j–n transition, and p–zc interference; H7/g6 is a close running fit.

Surface roughness Ra

The arithmetical mean deviation of the profile from the mean line, in micrometres. A number beside the check mark gives the maximum permitted Ra value.

Floor plan cut height

A horizontal section taken about 1.0 to 1.2 m above floor level, showing walls, openings, stairs, fittings and room labels at a typical scale of 1:100.

Building drawing scale selection

1:100 or 1:50 for plans and sections, 1:20 or 1:10 for construction details, and 1:200 or 1:500 for site plans.

Level symbol on drawings

A filled triangle with a value in metres relative to a datum, for example +0.450. Finished floor level is normally set as ±0.000.

Metric thread designation

M20 × 2.5 means nominal diameter 20 mm and pitch 2.5 mm. A coarse thread omits the pitch, written simply as M20.

Assembly drawing balloons

Parts are identified by leader lines ending in numbered balloon circles, cross-referenced to a parts list giving item, description, material and quantity.

Detail versus assembly drawing

A detail drawing gives full dimensions and tolerances for a single part. An assembly drawing gives overall, mating and functional dimensions only.

Technical lettering style

Single-stroke Gothic sans-serif capitals, vertical or sloped 15°. Notes are 2.5–3.5 mm high, subtitles 5–7 mm, and main titles 7–10 mm.

Freehand circle sketching

Draw light centre lines and a square, mark the four tangent points, then sketch arcs between them. Ellipses are sketched inside a parallelogram.

Model space versus paper space

Model space holds geometry at full size (1:1). Paper space layouts hold the title block and viewports set to the plotting scale.