Oblique Projections, Continued
Oblique
drawing
practices
In general, begin an oblique projection by drawing a centerline (CL) skeleton
and building the drawing on these centerlines. Make sure to construct all
points of tangency, particularly when you are planning to ink in the drawing.
Circles, arcs,
and ellipses
Objects with surfaces parallel to the plane of projection that contain circles,
arcs, and ellipses project in true size and shape. Circles not parallel to the
plane. of projection project as ellipses. Circles, arcs, and ellipses have no
transferable linear measurements and this requires you to inscribe the circle,
arc, or ellipse in. an equilateral parallelogram or square. Draw perpendicular
bisectors to the four sides of the parallelogram to locate the centers of the
circle or arc. This method works best in cavalier drawings because the
receding axis is drawn full scale. An alternate method of drawing a circle in
an oblique cavalier projection is by the alternate four-center ellipse method.
To draw a circle in oblique projection by the four-center method, use this
table:
Step
1
2
Draw a vertical and horizontal centerline with the horizontal center
line receding from the plane of projection.
Construct a circle equal in diameter to the actual circle using as a
center the intersection of the vertical and horizontal centerlines.
3
The constructed circle will intersect each centerline at two points.
From the two points on one centerline, draw two perpendiculars to
the other centerline.
4
5
From the two points on the other centerline, draw two
perpendiculars to the first centerline.
From the intersection of the four perpendiculars, draw four circular
arcs.
6
Darken all outlines.
Action
Continued on next page
6-9
