View stunning SlideShares in full-screen with the new iOS app!Introducing SlideShare for AndroidExplore all your favorite topics in the SlideShare appGet the SlideShare app to Save for Later — even offline
View stunning SlideShares in full-screen with the new Android app!View stunning SlideShares in full-screen with the new iOS app!
UNIT 2: “TECHNICAL DRAWING”1.- INTRODUCTION. A technical drawing is a form of graphic communication. This type of drawing is usedin the transformation of an idea into physical form. The process of creating a technicaldrawing is called drafting or technical drawing. A person who does drafting is known asa drafter. A technical drawing differs from a common drawing by how it is interpreted.A common drawing can hold many purposes and meanings, while a technical drawingis intended to concisely and clearly communicate all needed specifications of a createdobject or objects.Difference between technical drawing and artistic drawing: TECNHNICAL DRAWING ARTISTIC DRAWING The page is signed to become responsible The page is signed to become responsible of of the designed object. the artistic value from the picture. Paper sizes are standardized formats. Picture sizes are chosen by the painter. Rules are fulfilled. There are no rules. Technical drawings are only done in Painters usually use many colours. black. Only have one possible interpretation. Have many possible interpretations. Have measurements. Have no measurements.All of the above can be summarized by defining artistic design as "drawing done withthe intent or purpose to provoke emotions or feelings", and technical drawing as"drawing that aims to convey technical information about an object to manufacture."2.- DRAWING MATERIALS. The instruments of drawing are the tools we use to make technical drawings.The most important tools are:- PENCIL.It is a drawing instrument that consist of a cylinder of wood that contains a stick ofgraphite. According to the hardness of the graphite, the pencil can be classified by anumber or by numbers and letters. Look at the table:HARDNESSNUMBERS 0 1 2 3 4 5 6 7 8 9LETTERS 7B 6B 5B 4B 3B 2B B HB F H 2H 3H 4H 5H 6H 7H 8H Soft Middle Hard Extra-HardDrawing Pencils are a basic requirement of any graphics course. You need a number
39c739c737b6f7b6f5a6b5a6b396739673967396718631863186339671863396739675a6b39675a6b5a6b7b6f5a6b7b6f7b6f9c737b6f9c739c739c739c73bd77bd77bd77bd77de7bbd77de7bbd77de7bde7bde7bde7bde7bde7bde7bde7bde7bbd77de7bbd77bd77bd77bd779c73bd779c739c737b6f7b6f7b6f7b6f5a6b39673967734ee71cc61c0721c518c418e41ca314c418c418e51c061d0721e61ce61c071d492549258b2d49252821292109211863ff7f9c73bd77de7bbd77de7bde7bde7bde7bde7bde7bde7bff7fde7bde7bde7bff7fde7bde7bde7bde7bbd77de7bbd77de7b9c73bd779c737b6f5a6b39671863734e4a29a514a314c318a314c41cc418c518c418e51ce61cee39734ece398b2db456ff7fff7fff7fff7fde7bff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fff7fde7bff7fff7fff7fde7bff7fde7bde7bde7bff7fdd7bde7bbe77de7b7a6f14673367356b1467346b346b356b14671467146735671467356b1467356b356b356b1467566f356b356b1567356b1567356b356b366b3567356b1567366715673667156715671567356716677a6 Rapidograph by Rotring- TEMPLATES.Templates are special rulers which are used to draw symbols and do complicatedfigures.- THE GRADUATED RULER.A ruler is possibly one of the most important pieces of drawing equipment. Rulers areused to measure distances with lines..- SET SQUARESSet Squares are used to draw accurate angles. The most common are 45 and 60/30degrees.
A Set has an angle of 90 degrees and two 45 degree angles. It is used to make parallels,perpendiculars and draw angles.A Set Square has one 90 degree angle, one 30 degree angle, and one 60 degree angle).
- PROTRACTORA protractor is used to measure angles. A typical protractor is a semi-circular piece ofplastic with 180 degrees printed around its curve.3.- PAPER.Paper formats are the normalized sizes which we must use to do technical drawings.The normalized (or standardized) formats are: DIN A0, DIN A1, DIN A2, DIN A3,DIN A4, DIN A5 y DIN A6. The following rules are reflected in the following tables:a.- A format has twice size of the following format.b.- The length of a format is twice the width of the following format.c.- The width of a format is the same as the length of the following format.FORMAT LONG WIDEDIN A0 1188 840DIN A1 840 594DIN A2 594 420DIN A3 420 297DIN A4 297 210DIN A5 210 148DIN A6 148 105
4.- LABELLING.Labelling is the set of letters and numbers that accompany a technical or flat drawing.Labelling is standardized, in other words, the letters must be of fixed proportions, sothat no confusion can arise in the interpretation of the data. We only imitate this kind ofwriting as accurately as possible. It is used basically on two parts of the drawing, in thetitle box and the bounding.5.- STANDARDIZATION.Standardization is the set of rules or standards to follow when making a technicaldrawing or plan. Paper formats, the hardness of the graphite, production and placementof hearings or views, appropriate scales, the marking, labelling, line types, symbols, etc.All rules that exist are included in the drawing standards of each country, althoughdifferent rules have been unified to an international standard. Some rules of somecountries are U.N.E. (A Spanish standard), D.N.I. (German standard), U.N.I. (Italianstandard), I.S.O. (International standard).6.- TYPES OF LINES.The types of lines to be used in technical design is standardized, so each has a specificapplication. The types of lines that are used in industrial design and its applications arefollowing:Continuous thick:C Contours and edges are visible in views and perspectives. On the margins of drawing and painting or wall jack.Continuous thin: In auxiliary dimension lines and dimension.Freehand: In drawings and sketches.
Dashed: In contour and hidden edges.Dash-dot: . . . . . ... In lines of symmetry.7.- CROQUIS AND SKETCH. CROQUISSKETCHA sketch is a rapidly executed freehand drawing that is not intended to be a finishedwork, often consisting of a multitude of overlapping lines and there are no rules abouthow to sketch. The purpose of a sketch is to convey the best possible idea without goinginto details.A Croquis drawing is a quick and sketchy drawing with measurements (bounded) andproportioned. We usually use views.8.- STANDARD VIEWS.Technical drawing consists of representing objects which are three dimensional in thetwo dimensions on paper. To solve this problem, one of the tools used is viewpoint.We call a “View”, the shape of an object when viewed from a specific site, for example,the shape of the object from a certain position. As reflected in the next drawing, thereare six possible views that can be taken of any object.For a piece to be perfectly represented, we must follow these steps:1. Choose an elevation a view that offers further information about the shape of thepiece. This view is the main view. Any view can be chosen as elevation.
2. We can draw up to a total of six views, although if we draw the elevation, the left sideand the plant it is enough.3. The arrangement of the views is similar to the following figure:This is the image of an object in a box, with views of the object projected from thedirection of sight onto walls using first-angle projection. DThe views are positioned relative to each other according to either of two schemes:first-angle or third-angle projection. In each, the appearances of views may be thoughtof as being projected onto planes that form a 6-sided box around the objectThe name of the views:- View A: Elevation is an orthographic projection of a 3-dimensional object from theposition of a horizontal plane beside an object
- View B: Plan view or ground plan is defined as a vertical orthographic projection ofan object on a horizontal plane, like a map. It is viewed from below the elevation.- View C: Right side View. It is viewed from the left of the elevation.- View D: Left side View. It is viewed from the right of the elevation.- View E: Top view. It is viewed from over the elevation.- View F: Rear view. It is viewed from the right of the left side.* In the United States of America this is done in a contrary manner.8.1.- ELEVATION, GROUND PLAN (plan view), AND SIDE VIEW.When we draw an Orthographic view of the front of an object it is called anELEVATION.When we draw an Orthographic view of the top of an object it is called a GROUNDPLAN.When we draw an Orthographic view of the profile of an object it is called a SIDEVIEW.
• We draw a LEFT SIDE VIEW to the right of the elevation. • We draw a RIGTH SIDE VIEW on the left. Ground line9.- BOUNDING.An orthographic drawing is only complete when measurements, scale, and orthographicsymbols are added.To place dimensions on a multi-view drawing:Add measurements. Study the way these have been drawn on the front, side and planviews. It is very important to add measurements when drawing accurate orthographic orworking drawings. An orthographic drawing is usually the last drawing beforemanufacture and so dimensions must be clearly presented and understood. Dimensionscan also be applied to simple sketches and designs as they help anyone looking at thesedrawings to understand the overall size or scale. However, dimensions are usuallydrawn in a particular way and some examples are shown below:The dimension line has arrow heads and the dimension text is positioned above theline and is drawn using the current text style. (Continuous thin line).
The extension line is a line used to visually connect the ends of a dimension line to therelevant feature on the piece. Extension lines are solid and are drawn perpendicular tothe dimension line. (Continuous thin line). A leader line is a thin line with an arrow head that is often positioned at an angle and isused to tie a dimension to a feature, especially when there are space limitations.A Note is an additional instruction or general comment added to a blueprint. Notescontain information about the material, finish, tooling, tolerances, etc.A Center Line is a line used to define the center of a symmetrical part. Center linesconsist of alternating long and short dashes. chain thinThe main dimensioning rules are:1) The measurements are made in millimeters and focused on the dimension line and
never write the units. If at a dimensioned drawing is created with other units (cm, m) wewill post a note in the lower corner, near the title box.2) The benchmark figures (well labeled) are supported (without touching) the dimensionline, to read from the normal position of the plane (horizontal dimensions) and from theright (vertical dimensions).3) The arrows will be elongated and black, reaching the tip of the extension lines.4) Extension lines and dimension lines should not be cut.5) Extension lines protrude approximately 2 mm. from dimension lines.6) When we can, we will draw out the dimensions (text) of the piece.7) When a measurement is small, the arrows will be placed on the outside. If there aremany small measurements together, the arrows are replaced by dots.8) The dimensions must not be repeated, some measurements can be obtained by theaddition or subtraction of the others.9) To see if a piece is well bounded, we think about if we could build it.10) There are some symbols used in bounding to save us the trouble of drawing moreviews. The diameter sign "φ" represents a circular shape when it is not visible in theview. The same happens with other symbols like the square.“We can say that mastering the language of drawing, learning) the different types ofdrawings, achieving proficiency in the drawing of view), implementing the type ofline required i)each case, meeting the standards and bounding correctly, can only beachieved by practice. “So, all that we have learned about drawing will only be usefulif we practice by making drawings”.10. PERSPECTIVE.A second way to represent an object in three dimensions (height, width and depth) in the two dimensionsof the paper is known as perspective.To make these representations, technical drawing uses a system of three axes, indicating the threedirections in which the object will be drawn.To represent an object in three dimensions we use the isometric perspective or the cavalier perspective,although this course we will only study the cavalier perspective.10.1. CAVALIER PERSPECTIVE.This perspective has three axes. The X axis (width) and the Z (height) form a right angle, and the Y axis(D) form a 135 degree angle with both (X and Z).All edges that follow the direction of the height (Z axis) should be vertical and parallel.All edges that follow the direction of the width (X axis) are horizontal and parallel.
The same applies to the edges that follow the direction of the depth (Y axis).In the following figure we can see how the set squares are placed for drawing a figure in cavalierperspective more quickly and easily.When we draw the cavalier perspective of a piece we must take into account a very important rule, “thedimensions of the edges parallel to the axis Y (depth) are subject to a reduction coefficient K = 0.5”, ie,the edges should be drawn with (the) half of its actual measurement. If we do not reduce this axis (Y), theshape of the piece gives the feeling of having a size much larger than reality.For example: If the normal size is 25 mm. in depth (Y axis), we must reduce this axis (Y) before drawingit. The new measurement in Y is: 25 mm x K = 25 x 0,5 =12,5 mm.Fig. 1 (Normal size. Without reduction factor). Fig. 2 (With reduction factor)11. THE SHEET OF DRAWINGS OR PLANS.We have talked about the fact that in technical drawing we cannot use any type or size of paper. There arealso rules for the presentation of any technical drawings or, in other words, in developing a plan.In DIN A4, that will be our normal size drawing, we will draw a box with the following ranges:- On the left side 25 mm., in order to bind the paper if necessary.- At the top, bottom and on the right side 5 mm.At the bottom of the box we will draw another box divided into other boxes which we will call “title
box”. The role of the title box is to be able to place in the drawing, in an orderly manner, all theinformation related to it: who has drawn it, date, high school name, etc.(In your book you can find a title box drawn and bounded).DICTIONARY.For the development of our technical dictionary, you have to look for the meaning of these words, usingthis book first, in case you do not find them here, ask your family or look them up in a dictionary, butremember you have to write the definition with your own words. It’s not worth copying what it is writtenin your dictionary.Technical drawing - Set – DIN A4 - dashed line - thin continuous line – Title box - Standardization -Bounding - Sketch – Elevation.