Instrument Drawing and Lettering Techniques

Instrument Drawing Objectives in Drawing Accuracy Speed Legibility Neatness Typical Drawing Equipment

Instrument 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-Squares The T-square is made of a long strip called the blade, fastened at right angles to a shorter piece called the head.

Instrument Drawing The 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 the T-square. Drafting tape is used to fasten the drawing paper to the drawing board.

Instrument 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.

Instrument 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. HARD MEDIUM SOFT 9H 8H 7H 6H 5H 4H 3H 2H H F HB B 2B 3B 4B 5B 6B 7B Hard 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.

Instrument Drawing Drawing Lead Applications TASK LEAD GRADE LINE WEIGHT CONSTRUCTION LINES 3H, 4H, 6H THIN, LIGHT VISIBLE OBJECT LINES H, F, HB THICK, DARK HIDDEN LINES 2H, H THIN, DARK CENTER LINES DIMENSION LINES EXTENSION LINES LEADER LINES CUTTING PLANE LINES PHANTOM LINES LETTERING

Instrument 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.

Instrument 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.

Instrument 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.

Instrument Drawing Giant Bow Sets Giant bow sets contain various combinations of instruments. Giant Bow Compass The 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.

Instrument 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 radius Lean 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.

Instrument 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 compass The needlepoint extends about halfway into the paper when the lead touches the paper.

Instrument 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. .

Lettering Technique Lettering Techniques Most engineering lettering is single-stroke Gothic font. Lettering is drawn freehand and are drawn within light horizontal guidelines. 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. .