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Transcript of Drawing Instruments
Orthographic projection is a fundamental drafting technique. It is a means of representing the height, width, and depth of a three-dimensional object on paper. Three orthographic views are used in a multiview drawing to fully describe an object. However, additional views, such as an auxiliary view, may be required.
Three Principal Views
The three principal orthographic views in mechanical drafting are the top, front, and right side views. In architectural drafting, the views are basically the same with minor exceptions. The names are also slightly different.
Architectural Drafting Equipment
An Architectural drafter uses equipment that is designed for specific purposes. Using this equipment requires skill and understanding. Traditional drafting equipment, such as triangles, scales, compasses, etc., can be used to manually produce architectural drawings. A computer-aided drafting and design (CADD) system can also be used to produce a drawing on a computer, which is then plotted on paper.
Views and Elevations
The front view of an object in mechanical drawing is the same as the front elevation in architectural drawing. Note that the word"view" is changed to "elevation."
Architectural drafters ordinarily draw an elevation of all sides of the structure rather than just the front and right side, as is the practice in mechanical drafting.
After studying this chapter, you will be able to:
Define the three principal views in orthographic projection
List and explain the use of architectural drafting equipment.
Explain the difference between size and scale
Reproduce the standard alphabet of lines
Demonstrate an acceptable architectural lettering style
Identify the basic components of a CADD workstation
The floor plan is a section view taken about halfway up the wall
The top view of a house is called the plan view. There may be a roof plan, floor plan, foundation plan, and so on, developed from the basic plan view. The plan view of the floor plan in the most important view in architectural drafting.
These elevations are called the front elevation, right side elevation, left side elevation, and rear elevation. Some complex structures require more than four elevations to provide a complete description.
There are two principal types of pencils used in manual drafting - a common wood pencil and a mechanical pencil. Either type of pencil will give the desired results if keep sharp and used properly. The mechanical pencil allows the drafter to change the hardness of lead at will.
Most drafters prefer to use an eraser that is not attached to the pencil. Select an eraser that will remove all traces of lead without destroying the surface of the paper or leaving colored marks. Some pink erasers will leave a pinkish color that detracts from the appearance of the finished drawing. Plastic erasers are preferred by many drafters for this reason. Electric erasers can be used to quickly erase large areas or multiple changes.
Erasing shields are made of metal or plastic and are usually thin to provide for accurate erasing. The shield allows lines to be erased with removing surrounding lines. Always use the the erasing shield when there is a possibility of touching another line that you wish to save.
most architectural drawings are finished on some type of tracing paper, vellum, or drafting film. This allows for easy duplication of the drawings using traditional diazo machines. Preliminary drawings are sometimes made on opaque drawing paper and then later traced for reproduction.
Presentation plans are often completed on illustration board or some other special type medium designed for the particular artistic technique used in the presentation. As a general rule, the type of medium selected will depend on the intended use for which the drawing is being prepared and the presentation technique used.
Traditional drawing boards are made in standard sizes of 12" x 18", 18" x 24", 24" x 36", and 30" x 42". Most boards are white pine or basswood, or plywood with a vinyl cover. For those who still draft manually, drafting tables that have drawing-board tops are used most often. These tables are usually larger and have a drafting machine or straightedge permanently attached.
The t-square is a traditional manual drafting instrument. It is manufactured from wood, metal, plastic, or a combination of these materials. The t-square slides laong one edge of the drafting board and is used to draw horizontal lines. It also provides an edge against which triangles are placed to draw vertical and inclined lines. A t-square is used when a drafting machine is not available.
Triangles are used for drawing lines that are not horizontal. The 45 and the 30/60 degree triangles are the common triangles used in drafting work. Adjustable triangles are also available that take the common triangles place.
Protractors are used for measuring angles. They are produced in semicircular and circular styles. They are available in metal or plastic.
Scales used in drawing are primarily the architect's scale, engineer's scale and combination scale.
The architect's scale is usually divided into 3/32", 3/16", 1/8", 1/4", 1/2", 3/8", 3/4", 1", 1-1/2",and 3" to a foot. In addition, one edge is divided into 16 parts to the inch.
The engineer's scale is divided into 10, 20, 30, 40, 50, and 60 parts to the inch.
The combination scale is just what the name implies - a combination of the architect's and engineer's scales. It is divided into 1/8", 1/4", 1/2", 3/8", 3/4", amd 1" to the foot and 50 and 16 parts to the inch. Decimal measurements can be made using the 50 scale.
The most significant difference in these scales is that the divisions on the architect's scale are based on twelve units to the foot while the divisions on the architect's scale are based on twelve units to the foot while the divisions on the engineer's scale are based on ten units to the inch. The combination scale is designed to bridge the gap and provicedboth features.
How to Use a Scale
The use of words "size" and "scale" should be clarified. In drafting terminology, one may say the drawing is "half size." This means exactly what it says. The drawing is one half as large as the real object. If an object is 30 x 40. You would draw the object at 1/2 scale, 15 x 20. Most residential floors plans are drawn at 1/4 scale, where1/4" on the drawing equals 1'-0" on the house.
Study the 1/4 scale and notice the last 1/4" of the scale on the right-hand side. It is divided into twoe parts that represent the 12 inches of one foot. Be careful not to confuse the 1/4 scale with the 1/8 scale that appears on the same face, but starts from the opposite end. The 1/4 scale has longer lines denoting each foot.
The dividers are used to divide a line into proportional parts, provide a quick way to measure a length. Divider points are shaped like needles. They must be kept sharp to be useful.
The compass is used to draw circles, arcs, or radii. Some have center adjusting wheels and others have side adjusting wheels. Large arcs may be drawn using a beam compass.
Tjhe lead in the compass should be adjusted to the proper length, which is slightly shorter than the center point. Some practice is needed to draw sharp, smooth arcs. Hold the compass between your thumb and forefinger.
Guidelines are used to help neatly letter a drawing. Lettering guides are used to draw these guidelines. A common lettering guide is the Ames Lettering Guide.
Irregular curves are used to draw curved lines that cannot be drawn with a compass. When using an irregular curve, line up at least four points and draw the line through three. This procedure produces a smooth line.
The case instruments may include dividers, compass, lining pens, pencil pointers, spare parts, small screwdriver, and various other instruments.
Lettering devices are used when uniformity of letters is essential. Many styles and sizes of letters are available. Lettering in ink or pencil is possible with this type of lettering device.
Technical pens are used to ink a drawing. Pen points are interchangeable and range in size from 000 (very fine) to 8 (about 1/16" wide).
Templates serve as a guide in drawing special lines or symbols. The cutouts represent standard symbols and can be traced to form the symbol on the drawing. A wide variety of templates can be purchased in various scales to suit the requirements of most any drawing.
Grids are available in a wide variety of sizes and forms and have many uses in architectural drafting. Some grids are designed to be used under a sheet of tracing paper while others are designed to draw directly on it.
Square grids are useful in sketching idea plans and in modular construction drawings. Another type of grid used in architectural drawing is the perspective grid. These grids are quite useful and usually serve as underlays.
Freehand sketching is a method of making a drawing without the use of instruments. Most designers use sketches to "think through" an idea before an instrument or CADD drawing is made. It is also a useful technique for sharing ideas when an idea is still fluid and developing.
When sketching, hold the pencil with a grip firm enough to control the strokes. Your arm and hand should have a free and easy movement. The point of the pencil should extend approximately 1-1/2" beyond your fingertips. Use your third and fourth fingers to steady your hand.
As you sketch, rotate the pencil slightly between strokes to retain the point longer. Initial lines should be sharp and light, not fuzzy. When sketching straight lines, your eye should be on the point where the line will end. Use a series of short strokes to reach that point. When all the lines are sketched, go back and darken the lines. When darkening lines, your eye should be on the tip of the lead.
Strive for neatness and good technique when sketching, but do not expect a freehand sketch to look like an instrument drawing. Good freehand sketches have a character all their own.
Sketching Horizontal Lines
Horizontal lines are sketched with a movement that keeps the forearm approximately perpendicular to the line being sketched. Four steps are essential in sketching horizontal lines. First, locate the end points of the line. Next, position your arm for a trial movement. The, sketch a series of short, light lines. Finally, darken the line in one continuous motion.
Sketching Vertical lines
Vertical lines are sketched from top to bottom using the same short strokes in series as for horizontal lines. When making the strokes, position your arm comfortable at about 15 degrees to the vertical line. You may find it easier to sketch vertical or horizontal lines if the paper is rotated at a slight angle. A finger and wrist movement or pulling arm movement are best for sketching vertical lines.
Sketching Inclined Lines and Angles
All straight lines that are not horizontal or vertical are called inclined lines. To sketch inclined lines, sketch between two points or at a designated angle. Use the same strokes and techniques as for sketching horizontal or vertical lines.
Angles can be estimated accurately by first sketching a right angle (90 degrees), then subdividing it to get the desired angle.
Sketching Circles and Arcs
There are several methods of sketching circles and arcs - center line method, enclosing square method, hand-pivot method, and free circle method. All are sufficiently accurate, so use the method be suited for the particular situation
Six Steps are used in the center line method of freehand sketching circles. These steps are:
locate center lines, use a scrap piece of paper with radius marked to locate several points on the circle,position arm for trial movement, sketch the circle in short sweeps, and darken the circle.
The following steps are necessary when sketching a circle by e enclosing square method. First, locate the center lines of the circle. Second, sketch a box with the sides the same length as the diameter of the circle. Next, sketch arcs where the center lines meet the box Finally, sketch the circle
The hand pivot method is a quick and easy method of sketching circles. First locate the center of the circle. Next, using your small finger as a picot and holding the pencil in the normal manner, rotate the paper360 degrees. Your small finer should remain stationary on the center of the circle as you rotate the paper.
The free-circle method of freehand sketching circles involves more skill in performance, but can be developed with practice. Wtiht this method, you do not use any "guides" to help you sketch. You sketch the circle using only your hand-to-eye coordination.
Occasionally, it is necessary to sketch an ellipse. The rectangular method of sketching an ellipse is similar to sketching a circle with the enclosing square method. First, locate the center lines of the ellipse. Then, draw a box with side lengths equal to the major (longest) and minor (shortest) diameters of the ellipse. Next, sketch arcs where the center lines meet the box. Finally, sketch the ellipse
Sketching Irregular Curves
An irregular curve may be sketched freehand by connecting a series of points ar intervals of 1/4 " to 1/2" along its path. Include at least three points in each stroke. "Lead out" of the previous curve into the next by overlapping strokes.
Proportion in Sketching
There is more to sketching than making straight or curved lines. Sketches must contain correct proportions. Proportion is the relation of one part to another, or to the whole object. You must keep the width, height, and depth of the object in your sketch in the same proportion to that of the object itself. It not, the sketch may convey an inaccurate description.
A most useful technique in estimating proportions is the unit method. This method involves establishing a relationship between distances on an object by breaking each distance into units. Compare the width to the height and select a unit that will fit each distance. Distances laid off on you sketch should be the same proportion, although the units may vary in size. This method is especially useful when making a sketch from a picture of the object.
Drafting and Design
Computer-aided drafting and design (CADD) systems, like all computer systems, consist of hardware and software components. The hardware components of a computer system include the physical devices. The software programs are used by the drafter to create drawings or other documents. The computer hardware and software of a CADD is introduced in the following sections and discussed in detail in Chapter 5.
The basic hardware in most CADD work stations includes the central processing unit (CPU), input devices, storage devices, and output devices. The CPU is the "bra" of the computer system. Input devices provide for data and information input to the computer. The keyboard is the standard input device, but a mouse and digitization table are very useful in CADD work. Hard drives are generally the main storage devices on a computer.Some form of hardcopy output device, usually a plotter, is needed to produce prints of drawings.
Computer software is the programming (commands) that tells the copmuter hardware which tasks to perform. CADD software directs the computer to perform drawing and design tasks selected by the drafter/designer to draw lines, shapes, or symbols. Hundreds of CADD software programs are currently available that range from very simple programs to extremely complex architectural engineering and construction (AEC) programs.
To make a hard copyup of CADD drawings on paper or film, a plotter or printer output device is required. Pen plotters produce high quality drawings using pens or pencils of various colors. Plotters are available in sizes to accommodate standard paper sizes up through E-size (36" X 48"). Laser and ink jet printers also produce good quality graphic reproductions. However, most laser printers are limited in size to 11" x 14", which is too small for architectural applications. Ink jet printers and plotters are available in all sizes and can produce drawings in color.
Lines Used in Architectural Drawing
Architectural drafters use a number of different line types to ehlp the reader clearly understand the drawing. Drawings are usually made for a customer or as a presentation. It is for the purpose of accurate communication that specific line type is used in a given situation. Once a drafter learns these lines and uses them properly, communicating with others will be in a more precise manner. The purpose of a drawing is to communicate ideas accurately and clearly.
Drafters refer to the collection of line types used in drafting as the Alphabet of Lines. Many of the same line types used in mechanical or technical drafting are also used in architectural work.
Border lines are very heavy lines and are used to form a boundary for the drawing. They assure the reader that no part of the drawing is missing and provide a "finished" appearance to the drawing.
Object lines show the outline of the main features of the object. T are important lines and therefore should be easily seen. On an architectural drawing, such things as interior and exterior walls, steps, driveways, patios, fireplaces, doors, and windows are represented by object lines. The width of an object.
Hidden lines represent an edge that is behind a visible surface in a given view. In a floor plan, hidden lines are also used to indicate features above the cutting plane, such as an archway or wall cabinets in a kitchen. Hidden lines are not as thick as object lines.
Center lines indicate the center of holes and symmetrical objects such as windows and doors. Center lines simplify dimensioning, but should not be used as extension lines.
Extension lines are used to denote the termination point of a dimension line. They extend from a portion of the object to the dimension lines. Extension lines are thin lines, but are not construction lines. Therefore, draw them sharp and clear.
Dimension lines are used to show size and location. They are usually placed outside of the object. However, it is sometimes proper to place them within the object if the area is large and not too cluttered with other lines. All dimension lines have a dimension figure halfway between the ends with some form of symbol, such as an arrowhead, at the two terminal ends.
Long and Short Break Lines
Break lines are used to show that all of the part is not drawn. An example where a break line might be found is across a paved driveway indicating that the drive is longer than shown on the plan.
When the break is two or three inches in length, a long break line is usually used. Short break lines are used where part of the object is shown broken away to reveal an underlying feature or part of the object lines are thin and straight; short break lines are heavy and drawn freehand.
Cutting-plane lines are heavy lines used to show where the object is to be sectioned. Ordinarily, cutting-plane lines are labeled with a letter at each end a flag at one end and a direction arrow at the other so that the section detail will be easily identified.
Section lines or crosshatch lines are used to show that the feature has been sectioned. General section lines are usually drawn at a 45 egree angle. However, there are specific patterns to represent various types of material.
Guidelines are used for hand lettering. They are drawn very light and are for the drafter's use. Guidelines will help improve the quality of lettering and are, therefore, well worth the time and effort required to draw them.
Construction lines are very light used in the process of constructing a drawing. They are to help the drafter and should not reproduce when a print is made. Draw your construction lines sharp and light.
Line Type Application
This shows most of the general line types applied in a floor plan
Architectural lettering is not the same as mechanical or technical lettering. An Architectural drawing leans toward the artistic by nature. The "pure" letters used in mechanical drawing do not fit traditional architectural styles. Architectural lettering has more of an artistic flair.
There is not one correct architectural lettering style. Many acceptable styles present a certain artistic flair. Architects often like to develop their own personal style that is unique.
The space between letters in a word is not constant.The ability to judge the space between letters must be carefully learned. Only practice will perfect this ability.Constant practice in lettering words helps develop the ability to space letters in a pleasing attractive manner.
Proper spacing between words is as important as the spacing between letters. Words must not appear to run together, nor should they be so far apart that part of the drawing area is wasted. A good rule to follow in spacing words is to allow approximately a letter-height distance between words.
There are no absolute rules concerning leering size. Generally, most information lettering in architectural drawing is 1/8" or 32" high. A technique that looks good and helps in the readability of lettering is to make the first letter of each word 1/8" high and the remainder of the word 3/32" high. This emphasizes the beginning of each word and tends to separate them.
This is a lot to learn and remember,
but you did it. Next, work in teams to finish the Chapter 4 review.