Page 88 - CITS - ED - ELECTRICAL

ENGINEERING DRAWING - CITS

Holes for taking the bolts are of slightly larger diameter, ie; clearance holes of fine, medium and coarse series of
tolerance grades H12,H13 & H14 vide IS:1821. (Dimensions for clearance holes for bolts and screws)
NB: Recommended dia and Nominal lengths of bolts, screws, studs and thread lengths are available in IS:4206

Dimensions for width across flats for hexagon, hexagonal flanged bolts, screws and nuts ref IS:9519.
IS:1363 Part-1, 2 & 3 for Grade C
IS:1364 (Part 1 to 5) for Grade A and B of hexagonal bolts, screws and nuts.
Hexagonal socket head cap screw (IS:2269): These are available from M1.6 to M36 (16 sizes), length 2.3 mm
to 200mm depending upon the dia. It has the advantage over the other set screws, its hexagonal socket head
flushes in the metal, so the head does not project outside.
They are used on machine tables and on assemblies. (Fig 12) It is operated with an allen key.

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.

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CITS : Engineering Drawing (Electrician, Electronics Mechanic) - Exercise 6