--- In STMFC@..., "proto48er" <atkott@...> wrote:

In smaller scales, these nut/thread thingies are portrayed by a simple
rivet impression. Even in "O" scale, imported brass cars usually have
them portrayed as rivets.

Indeed! Not on an Accurail kit. Our Z braces have NUTS! Square nuts
just like the prototype. Even the resin kits I did years ago had
square nuts on the posts and bracing. Not that anyone can see them, If
you don't believe me, check out the Soo Line boxcar that Speedwitch is
now offering.

On the prototype, in summary, there are round rivets everywhere two
steel sheets are joined. There are nut/threaded thingies everywhere
wood is joined to steel. On a typical diagonal brace on a SS boxcar,
for example, there would be three or four round rivets at the top and
bottom (where it is joined to steel members) and the rest of the
fasteners on it would be the nut/threaded thingies!

Since I published my list of ANSI rivet sizes the other day, someone
was nice enough to forward me a sheet of specifications for AAR
rivets, ca. 1940. As I suspected,, the dimensions are substancially
the same as the ANSI spec., EXCEPT the AAR had sizes between the ANSI
sizes. Here is the expanded list:

AAR RIVET SIZES 1940

SIZE HEAD DIA. HO SCALE

1/4 .440" .005"
5/16 .546" .006"
3/8 .684" .008"
7/16 .765" .009"
1/2 .875" .010"
9/16 .985" .011"
5/8 1.094" .0125"
11/16 1.2" .014"
3/4 1.312" .015"
13/16 1.422" .016"
7/8 1.531" .0175"
15/16 1.641" .019"
1 1.750" .020"

It is important to note that the first column is the "trade size",
that is the nominal shank diameter. This is the size that will be
shown in Bills of Material, NOT the head size. The second column is
the head diameter, although the specification allows something like
+/- 1/16". The third column is the diameter of the dot on an HO scale
model that represents a rivet.

When trying to determine these sizes from prototype drawings, one will
often find the hole diameter specified, not the actual rivet. Keep in
mind that the spec. also allowed a tolerance on the rivet shanks that
guaranteed that all 1/2" rivets would not fit in 1/2" holes, so the
holes were specified oversize for clearance. Machinery's Handbook
recommends 1/16" oversize for clearance. The AAR spec. does not
concern itself with hole sizes.

As I said earlier. all the rivets I found on 1950's era freightcar
drawings were either 1/2 or 5/8, except for 3/8 on roof panels. These
would range in diameter on an HO scale model between .010" - .011",
with .008" on the roof. the actual head sizes A.T. Kott listed on
older cars seem to agree with these sizes.

Dennis