PRIN. OF DRAFTING AND SHOP DRAWINGS - OD1641 - LESSON 1/TASK 1
(4) Circles. Draw by marking the radius on each side of the center lines, then
sketch the circumference.
d. Procedure. A systematic order of application should be followed for both idea
sketches and sketches from objects. It is outlined as follows:
(1) Visualize Object. This is essential so that the mental image is definite and
clear and a good graphical description can be developed.
(2) Determine Views.
The views may or may not be the same as for a scale
drawing, depending upon the purpose of the sketch; e.g., a note in regard to the
thickness or shape of the section will often be used to save a view.
(3) Determine Size. A sketch should be in proportion to the sheet of paper. It
should be large enough to show all detail clearly, but allow plenty of room for
dimensions, notes, and specifications.
(4) Locate Center Lines.
Always locate the center lines first when beginning a
(5) Block in Main Outlines. Watch carefully the proportions of width to height
in this step. Select one edge as a unit from which to estimate the proportionate
lengths of the other edges.
(6) Complete Detail.
After the main outline is satisfactory, fill in the details
in correct proportion.
When the shape of the object has been
completely described, the dimension lines and arrowheads should be added.
measurements are taken until this step is completed.
Now the sketch is ready to have dimensions inserted on it.
These dimensions are obtained with a rule or a steel cable.
should be taken from finished surfaces.
(9) Titles and Notes. These should be inserted together with the date so that,
in the case of new inventions, it is possible to prove priority.