Projection Of Planes

Created By:- Viraj shah

Basic tools For EG

PensTraditional and typical pens used for technical drawing

are pencils and technical pens.Pencils in use are usually mechanical pencils with a standard lead

thickness. General line widths are 0.18 mm, 0.25 mm, 0.5 mm and0.7 mm. Hardness varies usually from HB to 2H. Softer lead gives a bettercontrast, but harder lead gives more accurate track.

Drawing boardThe drawing board is an essential tool. Paper will be attached and

kept straight and still, so that the drawing can be done with accuracy.Generally, different kind of assistance rulers are used in drawing. Thedrawing board is usually mounted to a floor pedestal in which the boardturns to a different position, and also its height can be adjustable. Smallerdrawing boards are produced for table-top use. In the 18th and 19thcenturies, drawing paper was dampened and then its edges glued to thedrawing board. After drying the paper would be flat and smooth. Thecompleted drawing was cut free. Paper could also be secured to thedrawing board with pins. More recent practice is to use self-adhesive tapeto secure paper to the board.

•T-squareA T-square is a straightedge which uses the edge of the drawing board as a

support. It is used with the drafting board to draw horizontal lines and to align otherdrawing instruments. Wood, metal, or plastic triangles with 30 and 60 degree anglesor with two 45 degree angles are used to speed drawing of lines at these commonlyused angles. Also in use are a continuously adjustable 0-90 degrees protractor. Analternative to the T-square is the parallel bar which is permanently attached to thedrawing board. It has a set of cables and pulleys to allow it to be positioned anywhereon the drawing surface while stil remaining parallel to the bottom of the board. Thedrafting machine replaces the T-square and triangles.

•Drafting machineA drafting machine is a device which is mounted to the drawing board. It has

rulers whose angles can be precisely adjusted with a controlling mechanism. There are two main types of apparatus: an arm-type parallelogram apparatus based on a hinged arm; and a track-type apparatus which moves on a rail mounted to the top of the drawing board. The accuracy of the arm type apparatus is better in the middle of the board, decreasing towards the edges, whereas a track machine has a constant accuracy over the whole board. The drawing head of a track-type drafting machine slides on bearings in a vertical rail, which in turn is moved along a horizontal, top-mounted rail. Both apparatus types have an adjustable drawing-head with rules attached to a protractor scale so that the angle of the rules may be adjusted.

RulersRulers used in technical drawing are usually made of polystyrene. Rulers come in

two types according to the design of their edge. Straight edge can be used with lead and felt pens, whereas when technical pen is used the edge must be grooved to prevent the spread of the ink.

An architect's scaleArchitect's scale is a scaled, three-edged ruler which has six different scales

marked to its sides. A typical combination for buildings details is 1:20, 1:50, 1:100, 1:25, 1:75 and 1:125. There are their own rulers for zoning work as well as for inch units. Today scale rulers are made of plastic, formerly of hardwood. A pocket-sized version is also available, with scales printed on flexible plastic stripes.

View of a drafting table: the old way of producing architectural and engineering drawings. On the top of the board is a paraller ruler

CompassThe compass is used for drawing circles or arc segments of circles. One form has

two straight legs joined by a hinge; one leg has a sharp pivot point and the other has a holder for a technical pen or pencil. Another form, the beam compass, has the pivot point and pen holder joined by a bar, useful when drawing very large radius arcs. Often a circle template is used instead of a compass when predefined circle sizes are required.

INTRODUCTION

A plane is a two dimensional object having length and breadth only. Its thickness is always neglected;

various shapes of plane figures are considered such as square, rectangle, circle, pentagon, hexagon, etc.

PROJECTION OF PLANES

Some of the planar projection are illustrated here

A Plane is a two dimensional entity having only lengthand breadth with negligible thickness which isconsidered as zero.TYPES OF PLANESPlanes may be divided as two main types. They are

(I) Perpendicular Planes(II) Oblique Planes.Perpendicular Planes

Planes which are perpendicular to any one of theprincipal planes of projection are called asperpendicular planes. These planes may be inclined orparallel to the other principal plane.

Various positions of perpendicular planes(a) Planes perpendicular to V.P. And Parallel to H.P.

Consider a plane perpendicular to V.P. And Parallel to H.P. The top view reveals the true shape of the plane

the front view is a line parallel to xy line.

(b) Planes perpendicular to H.P. And Parallel to V.P.Consider a plane perpendicular to H.P. And Parallel to V.P.

The front view shows the exact shape and size of the plane.The top view is a line parallel to xy line

(c) Plane perpendicular to both H.P. And V.P.Consider a plane in space which is perpendicular to

both the H.P & V.P.Both the front view and top view of the plane appear

as a straight lines on a single projector.

(d) Plane perpendicular to V.P. And inclined to H.P.

Consider a plane perpendicular to V.P. And inclined at an angle to the H.P. The top view is shorter than its ture size.

The front view is a line inclined at an angle to xy line .

(e) Plane perpendicular to H.P. And inclined to V.P.Consider a plane perpendicular to the H.P. And inclined at

an angle to the V.P. The front view is shorter than its true size.

The top view is a line inclined at an angle to xy line.

(f) Surface of the plane kept inclined to HP and VP or OBLIQUE PLANE Consider the plane to be inclined to both the surfaces that is the Horizontal plane and the Vertical plane

Example

A plate having a shape of an isosceles triangle has base 50mm and altitude 70mm. It is so placed that in the front view it seen as an equilateral triangle of 50mm side and one side is inclined at 45 deg to xy .

SOLUTIONFront view is seen as an equilateral triangle of 50mm side and one side is inclined at 45 deg to xyisosceles triangle has base 50mm and altitude 70mm.

Projections of Planes Peculiar problem wherein plane surface is inclined to both the planes Draw the side view and rotate the side view to get the true inclinations with VP and HP as well as the top view.

Don’t forget to denote the points with appropriate notations

Thank you