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The provisions of the thread in cad

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Yusuf

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 The provisions of the thread in cad
19-03-2014 11:39 . am | View his/her posts only
The provisions of the external thread drawing.
As shown in figure 8-2, the tooth top of the external thread is represented by the heavy line while the tooth bottom is represented by thin lines. In the view where does not reflect the round, you need to draw out the chamfer. In the thin solid line of the tooth bottom, you need to drawn the chamfer. The end line of the thread should be represented with the bold sold line while the end part of the thread don’t need to be drawn out. If you need to display the end of the thread, you can draw it out by the thin solid line which is 15 ° with the axis. In the proportion of illustration, the small diameter can be draw at 0.85 times with the large diameter. In the view of the round, the small diameter can be represented by the 3/4 thin sound arc. The chamfering round doesn’t need to draw.
The common mistakes is as figure 8-3 shows.
Figure 8-2 The provision drawing of the external thread.
Figure 8-3 Common errors in the external thread drawing
Conventional representations of the internal thread.
If you use the sectional view, the tooth top of the internal thread is represented by the thin lines while the bold solid line represent the tooth bottom. While, in the view which reflecting the round, the Large diameter is represented by the 3/4 thin solid round without the chamfering draw. If the object is the blind hole and the drawing method you use is proportional drawing, you can draw the distance from the terminate line to the end of the hole with the value which is 0.5 times than the large diameter. The cone angle at the end of the cone while drilling is draw with the angle of 120 degrees.(Figure 8-4)
You need to pay attention that the section line is the bold and solid line.
The requirements to the rest are same to the external thread.
Figure 8-5 shows the common error in the drawing.
8-4 Conventional representations of the internal thread.
Figure 8-5 Common Errors in the Internal Thread Drawing
The drawing of the screw of the internal and external thread (Figure 8-6). In section views, the screwing part of the internal and the external screw should be drawn according to the provisions of the external thread drawing. The non-overlap part need to draw according to their respective original provisional drawing method.
Figure 8-6 The drawing of the screw of the internal and external thread
Figure 8-7 The common errors in the screw drawing
It is important to note that the thin solid line of the internal thread large diameter, the bold solid line of the external thread large diameter as well as the bold and thin solid line of the small diameter in the internal and external thread should all be aligned. In addition, the solid screw line don’r draw by cutting in the section view where the section go through the screw axis.
Figure 9-7 shows the common error in the spin drawing

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