LAYOUTS AND LETTERING C H A P T E R T WO

OBJECTIVES 1. Identify six types of technical drawings based on the projection system they use. 2. Identify the line patterns used in technical drawings and describe how they are used. 3. Read and measure with the architects’ scale, engineers’ scale, and metric scale. 4. Identify standard drawing media and sheet sizes. 5. Add lettering to a sketch. 6. Fill in a standard title block

PROJECTIONS Behind every 2D drawing of an object is a space relationship involving the object and three “imagined” things: 1. The observer’s eye, or station point 2. The plane of projection 3. The projectors (also called visual rays or lines of sight). Perspective Projection Parallel Projection

Types of Projections There are two main types of projection: perspective and parallel. These are broken down into subtypes, as shown below:

Drawing Vocabulary A B C A B C Drawing Lines Lettering Measurement Systems Scale Title Blocks A B C A B C mm Inch Title Block

ALPHABET OF LINES Thick and Thin Drawing Lines Freehand line technique Line styles

FREEHAND LINES The main difference between an instrument or CAD drawing and a freehand sketch is in the appearance of the lines. A good freehand line is not expected to be precisely straight or exactly uniform, as is a CAD or instrument-drawn line. Freehand lines show freedom and variety. Freehand construction lines are very light, rough lines. All other lines should be dark and clean.

MEASUREMENT SYSTEMS U.S. Customary Units The Metric System Dual-Dimensioned

DRAWING SCALE Drawing scale is the reduction or enlargement of the drawn object relative to the real object Reduced and Enlarged Scale. Many drawings must be shown at reduced scale for the object to fit on the paper.

SPECIFYING THE SCALE ON A DRAWING For a part that is shown on the paper at half its actual size, the scale is listed in one of these three ways: SCALE: 1:2 SCALE: 1/2 SCALE: .5 Architectural drawings list the scale based on the number of fractions of an inch on the drawing that represent one foot on the actual object. Example: List the predominant drawing scale in the title block. (Courtesy of Dynojet Research, Inc.) SCALE: 1/8" 1'

SCALES Scales are measuring tools used to quickly enlarge or reduce Drawing measurements. Types of Scales

METRIC SCALES Full Size 1:1 scale The triangular scales have one full-size scale and five reduced-size scales, all fully divided. Using these scales, a drawing can be made full size, enlarged sized, or reduced sized. Half Size 1:2 scale

ENGINEERS’ SCALES An engineers’ scale (also called a civil engineers’ scales) is a decimal scale graduated in units of 1 inch divided into 10, 20, 30, 40, 50, and 60 parts. Because the engineers’ scale divides inches into decimal units, it is convenient in machine drawing to set off inch dimensions expressed in decimals.

MECHANICAL ENGINEERS’ SCALES Mechanical engineers’ scales are divided into units representing inches to full size, half size, quarter size, or eighth size. To draw an object to a scale of half size, for example, use the mechanical engineers’ scale marked half size, which is graduated so that ever ½” represents 1". In other words, the half-size scale is simply a full-size scale compressed to half size. Triangular combination scales are available that include full- and half-size mechanical engineers’ scales, several architects’ scales, and an engineers’ scale all on one stick.

Architects’ Scale The architects’ scale is intended primarily for drawings of buildings, piping systems, and other large structures that must be drawn to a reduced scale to fit on a sheet of paper. AutoCAD software users sometimes become confused using architectural units. When selecting architectural units and entering lengths, keep in mind that a value of 1 is one inch, not one foot.

LETTERING Lettered text is often necessary to completely describe an object or to provide detailed specifications. Lettering should be legible, be easy to create, and use styles acceptable for traditional drawing and CAD drawing. Engineering drawings use single-stroke sans serif letters because they are highly legible and quick to draw. Sans serif means without serifs, or spurs

An Example of Lettering and Titles Using CAD LETTERING STANDARDS Most hand-drawn notes use lettering about 3 mm (1/8") high. CAD notes are set using the keyboard and sized to be in the range of 3 mm (1/8") tall according to the plotted size of the drawing. An Example of Lettering and Titles Using CAD CAD drawings typically use a Gothic lettering style but often use a Roman style for titles. When adding lettering to a CAD drawing, a good rule of thumb is not to use more than two fonts within the same drawing.

Vertical Capital Letters and Numerals The proportions of vertical capital letters and numbers are shown

Vertical Lowercase Letters Lowercase letters are rarely used in engineering sketches except for lettering large volumes of notes. Vertical lowercase letters are used on map drawings, but very seldom on machine drawings. When large and small capitals are combined, the small capitals should be three fifths to two thirds the height of the large capitals.

Inclined Capital Letters and Numerals Inclined (italic) capital letters and numerals, are similar to vertical characters, except for the slope. The slope of the letters is about 68° from the horizontal.

FRACTIONS Do’s & Don’t Never let numerals touch the fraction bar. • Center the denominator under the numerator. • Avoid using an inclined fraction bar, except when lettering in a narrow space, as in a parts list. • Make the fraction bar slightly longer than the widest part of the fraction.

USING GUIDELINES Use extremely light horizontal guidelines to keep letter height uniform… Do not use vertical guidelines to space the distance from one letter to the next within a word or sentence. For even freehand letters: • Use 1/8" gridded paper for drawing to make lettering easy. • Use a scale and set off a series of spaces, making both the letters and the spaces between lines of letters 1/8" high. • Use a guideline template like the Berol Rapidesign 925 • For whole numbers and fractions, draw five equally spaced guidelines.

SPACING OF LETTERS AND WORDS Spacing between Letters Uniform spacing between letters is done by eye. Contrary to what might seem logical, putting equal distances from letter to letter causes them to appear unequally spaced. Spacing between Words Space letters closely within words to make each word a compact unit, but space words well enough apart to clearly separate them from adjacent words. Spacing between Rows Be sure to leave space between rows of lettering, usually equal to the letter height.

LETTERING FOR TITLES In most cases, the title and related information are lettered in title boxes or title strips When lettering by hand, arrange the title symmetrically about an imaginary centerline

DRAWING PENCILS High-quality drawing pencils help produce good quality technical sketches and drawings. Hard The hard leads in this group (left) are used where extreme accuracy is required, as on graphical computations and charts and diagrams. The softer leads in this group (right) are sometimes used for line work on engineering drawings, but their use is limited because the lines are apt to be too light. Medium These grades are for general-purpose work in technical drawing. The softer grades (right) are used for technical sketching, lettering, arrowheads, and other freehand work on mechanical drawings. The harder leads (left) are used for line work on machine drawings and architectural drawings. The H and 2H leads are widely used on pencil tracings for reproduction. Soft These leads are too soft to be useful in mechanical drafting. They tend to produce smudged, rough lines that are hard to erase, and the lead must be sharpened continually. These grades are used for artwork of various kinds, and for full-size details in architectural drawing.

Style of Pencil You might be surprised how much your drawings benefit from finding a style of pencil that suits your use. Soft pencils, such as HB or F, are mainly used in freehand sketching. Choose a pencil that: • Is soft enough to produce clear black lines, but hard enough not to smudge too easily. • Is not so soft that the point breaks easily. • Feels comfortable in your hand. • Grips the lead without slipping.

THE COMPUTER AS A DRAFTING TOOL Most people who create technical drawings use CAD. The advantages include accuracy, speed, and the ability to present spatial and visual information in a variety of ways. Even the most skilled CAD users need to also be skilled in freehand sketching, to quickly get ideas down on paper. One benefit of CAD is the ability to draw perfectly straight uniform lines and other geometric elements. Making changes to a CAD drawing takes about a tenth the time that it takes to edit a drawing by hand.

SKETCHING AND DRAWING MEDIA Many choices of media (paper and other) are available for particular sketching or drawing purposes. Whether you are sketching or are plotting a drawing from a CAD workstation, choose the type of sheet and size that suits your needs. Small notebooks or sketch pads are useful when working at a site or when it is necessary to quickly record information. Graph paper can be helpful in making neat sketches Sketch on Graph Paper

STANDARD SHEETS There are ANSI/ASME standards for international and U.S. sheet sizes. Note that drawing sheet size is given as height width. Most standard sheets use what is called a “landscape” orientation. * May also be used as a vertical sheet size at 11" tall by 8.5" wide.

Typical Sheet Sizes and Borders Margins and Borders Zones

Title Block The title block is located in the lower right corner of the format. Standard areas in the title block provide the information as shown below.

PLANNING YOUR DRAWING OR SKETCH When laying out a drawing sheet, you will need to consider: • the size and scale of the object you will show • the sheet size • the measurement system (units) for the drawing • the space necessary for standard notes and title block. The object you are drawing is the “star” of the sketch. Keep the object near the center of the sheet. It should be boldly drawn, using thick visible lines. Make it large enough to fill most of the sheet and so that details show clearly