Rivets: Size

Dennis Storzek

Here's a formula from Wayne Long:

The "size" of the rivet (in inches) is the outside diameter of the
shaft which goes into the two or more holes in the metal pieces
being riveted together. The diameter of the rivet head, where it
bears on a metal surface is size x 1.5 + 1/8". The head at its
highest point off the same metal surface is:
size x 1.5 + 1/8" x 0.425.

Apply this information to a standard 1" rivet and you get:

Shaft = 1" O.D.

Tom, List,

This got me curious, so I did some digging. Machinery's Handbook has
the ANSI specifications for solid steel rivets with button heads (at
least my mid-1980's edition has them). Wayne Long's formula is right
on for 1/2" rivets, but gives slightly large values for smaller rivets
and slightly small values for larger rivets. For instance, a 1" ANSI
button head rivet has a 1 3/4" head diameter. However Wayne's formula
is certainly close enough for our modeling, as the error in HO scale
would be less than .001". For those who care, here are the sizes of
the heads for ANSI Standard button head rivets, and their HO scale
equivalents:

1/4 .460" .0055"
3/8 .684" .008"
1/2 .875" .010"
5/8 1.094" .0125"
3/4 1.312" .015"
7/8 1.531" .0175"
1 1.750" .020"

I might point out that .020" dia. is the smallest size separate
styrene rivet that Tichy makes, and it models the head of a 1" rivet
in HO scale.

So, what size was used where? That's a rather had question to answer,
and took some searching. Typically rivet sizes aren't specified on
general arrangement drawings; one needs to go down to the component
drawings level to find them, and few of these are published. I went
back to that set of AAR drawings from the Field Manual / Interchange
Rules we were discussing the other day, and gleaned size
specifications from the call-outs on the roof, end, and door drawings.
Here is what I found:

The smallest I found was 1/4", used on the lap eams of the AAR flat
roof; similar to the PRR X29 roof, but note this is NOT the PRR
specification;

The rivets that attach the roof flange to the top of the end are
called out as 3/8";

The rivets that attach the ends of the roof seam caps to the side
plate, and side sheathing to the car posts in the door area are called
out as 1/2", all the rivets on the sides are drawn similar, but I
could not find a spec. other than at the door posts;

One of the ends called for 11/16" holes along its bottom edge, this
would be the clearance hole for 5/8" rivets;

Striker castings were attached with 3/4" rivets;

The largest rivets I found were from a different source, the ARA
(later AAR) standard for splicing steel center sills, which called for
7/8" rivets.

Nowhere did I find any 1" rivets specified, indicating that the Tichy
product is only good for bridge rivets in HO scale.

As an aside, in my design work at Accurail I've always used .010" -
.011" for rivet heads on car sides, slightly larger for frame rivets,
and these are indeed very close to scale for 1/2" rivet heads. I
suspect any rivets that look much smaller, the designer misinterpreted
the specified nominal size of the rivet for the actual diameter of the