Page 136 - CITS - ED - Mechanical

ENGINEERING DRAWING - CITS

Designation: A hexagonal socket cap screw of size M12 length 60 mm property class 12.9 shall be designated as
Hexagonal socket head cap screw M12 x 60-12.9-IS:2269.

Fig 11 Fig 12

Nuts and washers

Nut is a metallic piece of definite shape with threaded (screwed) hole on the centre of the face. It is used on the
end of the bolt/screw to hold the parts in position.
Nuts are known by their shape or their cross-section. The most commonly used forms are hexagonal and square.
Nuts are specified by the shape of the nut and the nominal dia of bolt/screw on which they are used. (Fig 1)
Fig 1

Hexagonal nut (Fig 2): it is made of hexagonal bar with a screwed/ threaded hole in the centre. To avoid the dam-
aging of the corners on the face, they are chamfered at 30 , with reference to the base. Theoretically the thickness
o
of the nut is equal to the diameter of the bolt and corner to corner is 2d i.e., twice the diameter of the bolt.
The actual sizes are specified in IS:1363, 1364, 3138.
Thin hex.nuts are available IS:1364 (Part-4).

Square nut (Fig 3): It is made out of square bar. Side of the square is equal to 1.5d + 3 mm and radius of the
chamfer is 2d. Sizes are from M6 to M39.
IS:2585 lays down the standard sizes available.

For drawing purposes, the following sizes of the nut are considered.
Bolt nom. dia = d
Thickness of nut T = d
Width across Flats W = 1.5d + 3mm
Angle of chamfer = 30 o
Radius of chamfer arc = 2d (approx.)

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CITS :Engineering Drawing (Mechanical) - Exercise 8