School of Technology

TECH 13580 - Engineering Graphics I

 

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ISOMETRIC DRAWING

 

MAJOR CONCEPTS 

A. Isometric = "equal measure" because each included angle at isometric axis = 120 deg. 

B. Isometric drawing not same as isometric projection. Isometric drawing is some what of a shortcut. Isometric projection is a category within Axonometric also including dimetric and trimetric. Axonometric is a subset of orthographic along with multiview projection. 

C. Volume of object is 100% for isometric drawing, but approximately 80% for isometric projection. If desired, isometric scale can be created to compensate .

D. Steps in making an isometric drawing .  Note use of 30 degree angle of 30-60 triangle used to construct drawing.

 

SELECTED TOPICS

A. Isometric lines are lines on or parallel to isometric axis used to delineate normal surfaces and are drawn true length.

B. Non-isometric lines are lines not on or not parallel to the isometric axis, are used to delineate inclined and oblique surfaces, are not true length, and can only be drawn by locating end points which exist on isometric lines then draw connecting line. 

C. Box construction method most frequently used by "boxing in" object's total height, width, and depth then removing unnecessary portions or adding features to create desired object. Appropriate method when object has mostly normal surfaces. 

D. Offset construction method used when most of object has inclined or oblique surfaces. Locate points by movement in space relative to height, width, depth as common to Cartesian math of X,Y,& Z.

E. Isometric circles are elliptical and drawn with isometric ellipse template or by approximate four-center ellipse method. Be sure major axis is correct direction when hole is on top, right vertical, or left vertical surface. 

F. Hidden lines in isometric usually are not drawn.

G. Reverse isometric axis to reveal underside of object if desired. 

H. Isometric sectioning  Study & know.

I. Dimensioning in isometric respects isometric planes. 

J. Step-by-step procedures to draw an isometric