(1) No matter what the tooth type of the external thread is, the projection of the thread crest circle is represented by a thick solid line; The projection of the root circle is represented by a thin solid line, and the chamfer or fillet part of the screw should also be drawn. When drawing, the small diameter can be approximately taken as dl≈0.85d d.

(2) The termination line of effective thread (thread termination line for short) is represented by thick solid line in the view; In the sectional view, the drawing method of the front view in Figure 9-8b (that is, the termination line only draws a short section of the height of the thread profile), and the sectional line must be drawn to the thick solid line representing the projection of the crest circle.

(3) In the projection plan view perpendicular to the thread axis (that is, the view projected as a circle), the thin solid line representing the bottom circle of the tooth is only drawn for about 3/4 turns (the position of about 1/4 turns is not specified), so the chamfer projection on the screw should not be drawn at this time. ?

Representation of internal thread

(1) No matter what the tooth type of the internal thread is, in the sectional view, the projection of the top circle of the thread is represented by a thick solid line, and the projection of the bottom circle is represented by a thin solid line. The thread termination line is indicated by a thick solid line. The section line should be drawn as a thick solid line, representing the projection of the top circle.

(2) In the view projected as a circle, the thin solid line representing the bottom circle of the tooth is only drawn for about 3/4 turns. At this time, the chamfer projection on the screw hole should not be drawn.

(3) When drawing non-penetrating screw holes, generally, the drilling depth and the depth of the threaded part should be drawn separately.

(4) When the line is invisible, all the lines are drawn with dotted lines, as shown in Figure 9- 10.