drafting - page 3 2. DRAFTING Drafting was previously a set...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
page 3 2. DRAFTING • Drafting was previously a set of techniques (using compasses, angles, T-squares, etc.) for creat- ing drawings that could be understood and used in manufacturing. • More recently drafting is focusing less on techniques and more on conventions, because of CAD systems. • The conventions of drafting are very important because they allow us to define parts in a way that they will be understood by any engineer, machinist, technologist, etc. 2.1 CONVENTIONAL DRAFTING • The purpose of drafting is to present technical ideas in precise and concise forms. • A properly drafted drawing should be understood by any engineer. • A sample of a drafted drawing is given below.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
page 4 2.1.1 Manual Drafting • This is the use of drafting boards, pencils, pens, and a number of specialized tools for drafting. While this method is still very popular, the techniques used in manual drafting are quickly being displaced by CAD (Computer Aided Design) systems. • I will not cover some of the manual drawing topics list below, but more information on them appears in a large number of drafting books. - lettering - hand sketching - drawing ellipses - etc A A section A-A 2.50 0.25 Ø2.00 Ø1.62 1.750 Ø0.006 M Ø1.0005/0.9995 Ø0.25 2 Notes: 1. Break sharp edges to 0.01 max. Drill Ø0.985 ream to spec. 2 part: bushing date: etc. ...
Background image of page 2
page 5 2.1.2 Turning Three Dimensions Into Two (Multi View Drawings) • The problem with drafting is that the paper is flat, while the object drawn is not. • To get around this we can develop a number of views to work with. - Front View - Top View (Plan View) - Right Side View - Left Side View • This method of developing views is known as Orthographic projection • This method eliminates the perspective distortion in real vision, thus making it easier for techni- cal depiction. • In this method, object faces that are parallel to the viewing plane are shown as actual size, but objects that are not parallel are foreshortened. • The number of views used is a function of the geometry. For a simple object such as a washer, only one view is needed. A more complicated object, such as a piston, would require at least two views. 2.1.2.1 - The Glass Box • The views are developed as if a glass box was placed over the object. The view from each direc- tion was frozen, and when the box is unfolded, the resulting views are seen. • Imaging the case below of a small tetrahedron (a three pointed triangle),
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
page 6 • The drawings are layed out with certain conventions. The example above is continued below for illustration, In the figure extra construction lines are added to show how the drawings in the different views are related.Note that the top view is related to the side view using a 45° line. These properties are a result of the ‘glass box’ concept. The folding lines are often shown on drawings (they have two dashes and one long). Also note that in the figure shown below, the points in the top view will be the same distance from the folding line as they are in the side view.
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 07/20/2008 for the course MECH&AE 94 taught by Professor Jain during the Spring '08 term at UCLA.

Page1 / 44

drafting - page 3 2. DRAFTING Drafting was previously a set...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online