If the dimensions of rivets are not specified on the design drawing, you can determine the rivet size based on the following rules:
Minimum Diameter of Rivet Shank (D) = 3 x Thickness of the Thickest Sheet That is Being Joined
A=1.5 *D (For rivets of diameters of the rivet shank up to 20 mm)
Length of Rivet Shank (L) = S + Allowance (A)
A general rule is that the rivet should have a diameter of at least three times the thickness of the thickest sheet that is being joined. Please note that the value of D (diameter) is the minimum option of the rivet shank diameter, and the rivet shank must be longer than the thickness of all materials to be riveted, otherwise, there will be no allowance for fastening. According to the military standard, so the bucked counter head diameter of the rivet joint must be larger than 1.4 times the diameter of the shank. The allowance depends on the type of rivets and applications. Then how to determine the correct size of rivets?
For example, two pieces of the 0.060-inch sheets are to be riveted together. The proper diameter rivet would be 3 x 0.060=0.180 inches.
A 3/16” rivet (0.188 inches) should be used. The metal thickness is 0.060+0.060=0.12 inches, and 1.5D is 1.5 x 0.188 inch = 0.282 inches, so the total length would have to be 0.12 + 0.282=0.402 inches for the rivet.