Projections commonly used


The standard method of representing a three­dimensional object in two-dimensional form, i. e. as a scale drawing on one plane, is by ortho - graphic projection in which related views give the various aspects, viz.:

Plan Representation of the object on the horizontal plane, i. e. looking down.

Front and side elevations Representation of the object on the vertical plane, i. e. level with the eyes.

Section The object cut through either on the horizontal or the vertical plane to show details which would not be visible in simple outlines of plan and elevation. Vertical sections are usually included in a side elevation projected from the front elevation, and horizontal sections included in the plan, although if the object is complex several such sectional drawings may be necessary.

All these drawings are to a convenient scale, but full - or half-size details are necessary for free-hand curves where a compass radius cannot be stated, or where the particular detail calls for amplification.

They can be projected from either the first dihedral angle (first angle drawings) or the third dihedral angle (third angle drawings), and 331:1 gives a typical layout using the first angle and drawn to a scale of 1/8 (11/2 in to the foot) or to metric scale. The details given show, at 331:lB, the front elevation of a simple wooden plinth with a circular recess on the face for an inlaid metal plaque; 331:1 A is the plan of the plinth showing a stepped housing for a statuette; and 331:lC a vertical side section on the centre-line XY (331:1 A). Full-size details of the stepped housing and the circular recess are shown in 331:lD and 331:lE and no further information should be necessary. Where the drawings are of complex objects, however, it may be necessary to add a three-dimensional project for clarification.

First-angle projection

Where a horizontal plane intersects a vertical plane (VP) dihedral angles are formed, of which both the first and third angles are used in orthographic projection. Where the first

dihedral angle is used (332:1) the object is placed between the observer and the vertical plane (332:2), thus the front elevation is seen first (the arrow points the direction), the side elevation is projected from it by folding back the side vertical plane on the vertical trace (VT), and placing it alongside the front elevation. The horizontal plane is then folded down on the horizontal trace (HT) XY, known as the XY line, and therefore appears below the front elevation.

Third-angle projection

This method is becoming increasingly popular, although it hardly matters which method is adopted provided the drawing is quite clear as to what it is intended to represent. In third angle projection the object is placed behind the vertical plane (332:3), the plan is seen first, the front elevation below it, and the side elevation projected alongside the front elevation.

Добавить комментарий



Where no previous records are available the proprietor must assess his own capabilities and those of his employees. Common joinery items are usually in softwood of fairly large dimensions, with …

Costs of man-hours

The total cost of man-hours at the rates paid, plus overtime rates where applicable, plus health insurance, pensions, paid holidays, etc. have to be considered. Here again these may be …

Appendix: Costing and estimating

Costing is the pricing of completed work taking into account not only all the direct expenses— materials, wages and insurances, fuel and power, machining costs, workshop expenses, etc.—but also a …

Как с нами связаться:

тел./факс +38 05235  77193 Бухгалтерия
+38 050 512 11 94 — гл. инженер-менеджер (продажи всего оборудования)

+38 050 457 13 30 — Рашид - продажи новинок
Схема проезда к производственному офису:
Схема проезда к МСД

Партнеры МСД

Контакты для заказов шлакоблочного оборудования:

+38 096 992 9559 Инна (вайбер, вацап, телеграм)
Эл. почта:

За услуги или товары возможен прием платежей Онпай: Платежи ОнПай