Question

what is the meaning of white circle and black circle in Table 5 of standard IS1367 part 3.

Answer 1

This symbol is used to denote the bolt and screw diameter.

white circle denotes the bolt and screw with thread diameter , $d\leq3$ mm or

length, $l\leq$ 2.5 mm

and black circle denotes the bolt and screw with thread diameter, $d>3 mm$ or

length, $l\ge2.5 mm$ as per Table 5 of standard IS1367 part 3.