A Text Book on Engineering Graphics - Central Board of Secondary ...

Solution
D = 0.96 P
D
6
d = 0.64 P
D
6
Steps Involved
P
40
P
55°
Fig 2.5
0.5 P
MACHINE DRAWING
BRITISH STANDARD WHITWORTH THREAD (B.S.W. THREAD)
(i) Draw vertical centre lines separated by the distance of P/2, (P/2=20 mm).
(ii) Draw two horizontal lines separated by a distance of major diameter D=0.96P.
(iii) One sixth of 'D' is cut off parallel to the axis of the screw at top and bottom, to draw
the horizontals for minor diameter, d= 0.64P.
(iv) Draw the basic or fundamental triangles within the D lines, such that the angle
between the flanks is 55°.
(v) Draw arcs at crest and roots, to make it round by any suitable method. The method
is shown clearly in FIG 2.5, or radius of the arc can be taken as r= 0.137P.
(vi) Complete the profile and hatching is done as shown in FIG 2.5, to represent the
external thread.
(vii) Standard dimensions are to be done as shown in the above figure.
D
38.4
46 ENGINEERING GRAPHICS
d
25.6
D/6
6.5