MATSEC IM Engineering Drawing and Graphical Communication flashcards

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

First-angle projection symbol

A truncated cone drawn with two concentric circles on the left and its side elevation on the right. It indicates that views are placed behind the object, as used in ISO and European practice.

Scale 1:10

A reduction scale in which one unit on the drawing represents ten units on the object. A 50 mm drawn length therefore corresponds to a 500 mm real length.

Line precedence rule

When lines overlap, visible outlines are drawn first, then hidden outlines, then centre lines, then dimension and extension lines. This keeps the part shape readable on a busy drawing.

Perpendicular bisector construction

With a radius greater than half the line, strike equal arcs from both endpoints above and below. The straight line joining the two arc intersections is the perpendicular bisector.

Ellipse focal property

An ellipse is the locus of points whose distances to two foci sum to a constant equal to the major axis 2a. The minor semi-axis satisfies b squared equals a squared minus c squared.

Cycloid construction

A cycloid is traced by a point on a circle rolling along a straight line. Divide both the generating circle and the base line into the same number of equal parts before projecting.

Mitre line in orthographic views

A 45 degree line drawn from the intersection of the reference planes. It transfers depths from the plan to the side elevation, keeping the two views consistent.

Hidden detail line

A dashed thin line showing an edge that exists but cannot be seen in the current view. Dashes meet at corners and are omitted where they would clutter the drawing.

Choosing the front view

Select the viewing direction that shows the most characteristic shape with the fewest hidden features, and place the longest dimension horizontally. Other views follow from this choice.

Isometric scale factor

True lengths are 0.816 times the lengths drawn along the isometric axes, because the axes are equally inclined to the projection plane. Isometric drawing often ignores this and uses full scale.

Isometric circle ellipse axes

A circle on an isometric face becomes an ellipse with major axis 1.22 times the diameter and minor axis 0.71 times the diameter. The major axis lies perpendicular to the face normal.

Cabinet oblique projection

The front face is drawn true shape and size, while receding edges are drawn at an angle, usually 45 degrees, at half scale. This reduces distortion compared with cavalier projection.

Dimension line placement

Thin continuous lines with arrowheads at each end, placed outside the outline where space allows. Numerals sit above the line and read from the bottom or right edge.

Hole basis H

In ISO limits and fits, uppercase H denotes a hole whose lower deviation is zero. The shaft letter and grade then determine the clearance or interference of the fit.

Geometric tolerance frame

A rectangle divided into compartments holding the characteristic symbol, the tolerance value in millimetres, and datum letters. A leader connects the frame to the controlled feature.

Surface texture Ra symbol

A tick symbol carrying the Ra value in micrometres. A circle inside the tick means material removal is not permitted; a bar across it means removal is required.

Hatching in section views

Thin continuous lines at 45 degrees to the principal outlines, evenly spaced, showing cut material. Adjacent parts in an assembly use different angles or spacings for contrast.

Parts not sectioned longitudinally

Shafts, bolts, nuts, rivets, keys, pins and similar standard components are left unsectioned when the cutting plane passes along their axis, so their outline remains clear.

Auxiliary view purpose

A view projected on a plane parallel to an inclined face, so that face appears true shape and size. Depths are transferred from the view in which the face appears as an edge.

Cone development sector angle

For a right cone, the pattern is a sector of radius equal to the slant height. Its angle is 360 degrees multiplied by base diameter divided by twice the slant height.

Metric thread designation

M20 x 2.5 means a metric thread of 20 mm nominal diameter and 2.5 mm pitch. A coarse thread omits the pitch, and LH indicates a left-hand thread.

Bearing bore number rule

The last two digits of a rolling bearing basic number give the bore in units of 5 mm. A 6205 bearing therefore has a bore of 25 mm.

Gear module formula

Module equals pitch circle diameter divided by the number of teeth. Addendum equals the module, dedendum equals 1.25 times the module, and outside diameter equals module times teeth plus two.

Assembly drawing contents

All components shown in position with item numbers, a parts list giving description, quantity and material, overall dimensions, and a title block. Detail drawings carry individual part dimensions.

Fillet weld symbol

A right triangle placed on the reference line, with the leg size written before the symbol. Symbols above the line apply to the arrow side, below to the other side.

Pie chart sector angle

The angle for a category equals 360 degrees multiplied by the category value divided by the total. All sectors together must complete the full circle of 360 degrees.

Histogram versus bar chart

A histogram shows the frequency distribution of continuous data with adjacent bars on a measured axis. A bar chart compares separate categories and leaves gaps between bars.

Graph axis labelling

Each axis carries the quantity and its unit, for example Time / s, with equal scale increments and a stated step. The independent variable is placed on the horizontal axis.

Flow chart decision symbol

A diamond indicates a decision point with two or more exits, each labelled with a condition. Ovals mark start and stop, rectangles mark processes, parallelograms mark input or output.

Broken-out section

A local section bounded by a freehand break line, used to expose an internal feature without sectioning the whole object. It suits small details on large parts.

Chain thin line use

Chain thin lines mark centre lines, axes of symmetry, pitch circles and cutting plane traces. They extend slightly beyond the feature and are not used for visible outlines.

True length by rotation

An inclined line appears true length when rotated parallel to a reference plane in one view. Alternatively, construct a right triangle using plan length and height difference.

Exploded pictorial view

A pictorial drawing with components separated along their assembly axes, linked by thin chain lines. Item numbers connect each part to the accompanying parts list.