Page 155 - CITS - ED - Mechanical

ENGINEERING DRAWING - CITS

In butt joint, the thickness of cover plates or strap with respect to plates being joined is
– single strap = 1.125t
– double strap = 0.6t to t
"Chain riveting" and zig-zag riveting: When the rivets in the rows are placed directly opposite to each other it
is called chain riveted. (Fig 5a) If rivets are staggered it is called zig-zag riveted. (Fig 5b)
The distance between the rows of rivets is called "Row pitch" Pr. The value of row pitch (Pr) in the case of chain
riveting is 0.8 P and 0.6 P for zig-zag riveting.
The distance between the centre of one rivet in one row to the centre of the nearest rivet in the adjoining row is
called diagonal pitch - Pd (Fig 5b)

Fig 5

The figures show the double riveted butt joint (zig-zag) double strap.
Boiler shells plates are joined by riveted joints as in Fig 6.
Chaulking and Fullering: Due to high internal pressure of steam or water in the boiler, there is the possibility of
the leakage of steam or water through rivet holes or joint i.e., between plates. To prevent such leakages the rivet
heads and plate ends are firmly forced together. It is called chaulking and fullering. For caulking a blunt type
chisel is used by hammering the rivet head/plates. (Fig 7a)

In fullering a tool with thickness equal to that of plate is used to hammer the edges of the plate. It is used to press
the plate ends. (Fig 7b)
Figures 8 show how the plates at right angles can be joined using rivets.

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CITS :Engineering Drawing (Mechanical) - Exercise 8