3Instrument Drawing Drawing Boards The left edge and right edge of a drawing board has a true straight edge.For right-handed people, the left-hand edge of the board is called the working edge because the T-square head slides against it.For left-handed people, the right-hand edge of the board is called the working edge because the T-square head slides against it.T-SquaresThe T-square is made of a long strip called the blade, fastened at right angles to a shorter piece called the head.
4Instrument DrawingThe drawing paper should be placed close to the working edge of the board to reduce any error resulting from the bending of the blade of the T-square.The paper should also be placed close enough to the upper edge of the board to permit space at the bottom of the sheet for using theT-square.Drafting tape is used to fasten the drawing paper to the drawing board.
5Instrument Drawing Drawing Pencils High-quality drawing pencils should be used in technical drawing, never ordinary writing pencils.Many makes of mechanical pencils are available together with refill leads in all grades. Choose a mechanical pencil that feels comfortable in your hand.
6Instrument Drawing Drawing Leads The first consideration in the selection of a grade of lead is the type of line work required. For light construction lines and guide lines for lettering use a hard lead. For all other line work, the lines should be BLACK. The lead chosen should be soft enough to produce jet black lines but hard enough not to smudge.HARDMEDIUMSOFT9H 8H 7H 6H 5H 4H3H 2H H F HB B2B 3B 4B 5B 6B 7BHard leads are used where extreme accuracy is required. Generally these leads are used for construction lines.Medium leads are used for general purpose line work in technical drawing.Soft leads are used for various kinds of art work. These leads are too soft to be useful in mechanical drafting.
7Instrument Drawing Drawing Lead Applications TASK LEAD GRADE LINE WEIGHTCONSTRUCTION LINES3H, 4H, 6HTHIN, LIGHTVISIBLE OBJECT LINESH, F, HBTHICK, DARKHIDDEN LINES2H, HTHIN, DARKCENTER LINESDIMENSION LINESEXTENSION LINESLEADER LINESCUTTING PLANE LINESPHANTOM LINESLETTERING
8Instrument Drawing Drawing Horizontal and Vertical Lines To draw a horizontal line, press the head of the T-square against the working edge of the board with your left hand. Lean the pencil in the direction of the line at an angle of approximately 60º and draw the line from left to right. While drawing the line, rotate the pencil to distribute the wear uniformly on the lead to maintain a symmetrical point.To draw a vertical line, press the head of the T-square against the working edge of the board with your left hand and place a triangle against the blade of the T-square. Lean the pencil in the direction of the line at an angle of approximately 60º and draw the line upward, rotating the pencil to distribute the wear uniformly on the lead to maintain a symmetrical point.
9Instrument Drawing Triangles Most inclined lines are drawn at standard angles using the 45º x 45º triangle and the 30º x 60º triangle.In addition to drawing angles of 90º, 45º, 30º, and 60º, triangles can be combined to draw angles of 15º increments.
10Instrument Drawing Scales Scales are instruments used in making technical drawings full size or at a given reduction or enlargement.Types of scales include metric scales, engineers’ scales, decimal scales, mechanical engineers’ scales, and architects’ scales.Scales are usually made of plastic or boxwood and are either triangular of flat in shape.
11Instrument Drawing Giant Bow Sets Giant bow sets contain various combinations of instruments.Giant Bow CompassThe giant (large) bow compass has a center wheel and can be adjusted simply by opening or closing the legs of the compass while turning the center wheel.
12Instrument Drawing Using a Giant Bow Compass Set off the required radius on one of the center lines.Place the needle point at the exact intersection of the center lines.Adjust the compass to the required radiusLean the compass in the direction that you are going to draw the circle. Draw the circle in a clockwise direction while rotating the handle between the thumb and forefinger.
13Instrument Drawing Sharpening the compass lead A properly sharpened compass point is formed by rubbing the lead on the sandpaper pad.A properly sharpened compass point consists of a single elliptical face.A properly adjusted compassThe needlepoint extends about halfway into the paper when the lead touches the paper.
14Instrument Drawing Pencil Drawing Techniques A quality drawing is characterized by crisp black line work and lettering.All finished pencil lines should be very dark. Construction lines should be made very light so that they need not be erased when the drawing is completed.Contrast in pencil lines should vary in the widths of the lines. Visible object lines should contrast strongly with the thin lines of the drawing..
15Lettering Technique Lettering Techniques Most engineering lettering is single-stroke Gothic font. Lettering is drawn freehand and are drawn within light horizontal guidelines. Typically lettering is 1/8” high.All lettering uses upper case letters. Lower case letters are rarely used in technical drawings.There are three aspects of good lettering: proportions and forms of the letters, composition and spacing, and practice.There are six fundamental drawing strokes and their directions in basic lettering. Horizontal strokes are drawn from left to right, vertical strokes are drawn from top to bottom, and curved strokes are drawn downward..