Drafting Objective 4.03 Explain the terms and procedures utilized in technical sketching

Drafting Drafting is the process of accurately representing three- dimensional objects and structures on a two-dimensional surface, usually paper. It is an accurate drawing process used for nearly every product or structure made today – large or small.

Drafting Goal To describe an object or structure so accurately that someone else that someone else can use the drawing to create it. Drafters use different types of drawings to achieve this goal.

Drawing Lines Object Lines Hidden Lines Center Lines Extension Lines Dimension Lines

Object Line The lines that outline the object and its major details must stand out. Solid Lines Darkest lines on all drawings

Hidden Lines Some details are hidden in one or more views They are shown but with lighter, dashed lines called hidden lines.

Center Lines Locates holes and arcs on a part. These lines pass through the center of the hole and are thus called center lines.

Extension Lines Indicate the points from which the measurements are taken. Between the extension lines are the dimension lines.

Dimension Lines These have arrows pointing to the extension lines that indicate the range of the dimension. The dimension and extension lines are the same weight as hidden Lines.

Sketching Three Types Rough Sketches Refined Sketches Detailed Sketches

Rough Sketches Rough Sketches – It suggests that the designs are incomplete and unrefined. The term “rough” is not used to describe the quality of the drawing. They often represent good sketching techniques.

Rough Sketch

Refined Sketches Refined Sketches- The 2nd step in developing a design solution. Developed by merging ideas from two or more rough sketches into a refined sketch. The new idea may not look anything like the original. The rough sketch and the refined sketch communicate shape and proportion. They do not communicate size.

Refined Sketches Two Or More Rough

Detailed Sketches Detailed Sketch- A detailed sketch communicates the information needed to build a model of the product or structure. Building requires three major types of information Size information Location information Geometry information.

Three Major Types of Information Size Information – Explains the overall dimensions of the object, or the size of the features of an object. Location Information – Gives the position of the features within the object. Geometry information- describes the geometric shape or relationship of features on the object.

Pictorial Sketches Pictorial Sketches – Three basic techniques are used to develop pictorial sketches Isometric Oblique Perspective

Oblique Sketches Oblique Sketches - The easiest pictorial sketches to produce. They show the front view as if a person was looking directly at it. The side and top extend back from the front view. They are shown with parallel lines that are generally drawn at 45 degrees to the front view. The two types of oblique drawings are cavalier and cabinet

Two Types of Oblique Sketches Cavalier Oblique drawing- causes the sides and top to look deeper than they are. To compensate for this appearance cabinet oblique drawings are often used. Cabinet Oblique Drawing- This type of drawing shortens the lines that project back from the front to one-half their original length.

Isometric Sketches Isometric Sketches – The second type of pictorial drawing used to produce refined sketches. The term isometric means equal measure. Isometric sketches get their names because the angles formed by the lines at the upper right corner are equal - each is 120 degrees. The object is showed as if it were viewed from the corner.

Perspective Sketches Perspective Sketches – show the object as the human eye or camera would see it. This realism is obtained by having parallel lines meet at a distant vantage point. Developing the perspective view is more difficult to draw than oblique or isometric views. However, perspectives are the most realistic of the three sketches.