By Chris Wantuck
There are many hardware fasteners that have appeared in the automotive trade ranging from square head nuts and bolts, Phillips head screws to today's Torx fasteners. As our restoration projects continue to challenge us, we continue to seek hardware and fasteners to overcome problems. Helicoils are a good example and to this list we can add the Threaded Rivet or Slot-less Screw. It is a simple fastener that has the appearance of a rivet, a domed head with no visual signs of using a tool to tighten its grip. Down its shank, it has standard US threads that accept common nuts. They can be used to fasten hardware or panels just as a regular machine screw might be used. While the threaded rivet is not necessarily new, the use for trunk restoration is one application that should be considered.
Automobiles, beginning in the teens through the 1930's, included a box like container on a special rack to store personal articles, spare auto parts, or reserve fluids like gas, water or oil. These trunks evolved into special sizes and features to appeal to the car buyer and to accommodate the auto manufacturer's manufacturing process. They often included long piano hinges, strap hinges, latches and decorative metal strips. All these hardware items were originally fastened using a lead covered nail. Over the years these nails would loosen and the hinges and hasps would fall off, essentially making the trunks useless. Using threaded rivets instead of nails provides a significantly better way to fasten the trunk's hardware. The holding strength of the threaded rivet is superior to that of nails, especially if the wood has been weakened from previous nail holes.
Threaded rivets are available in a variety of screw sizes of 4-40, 6-32, 8-32, 10-32 and 1/4-20 and most sizes have head shapes of either round or truss head. Length's vary from 3/8 inch for the smaller 4-40 to one inch long for the 1/4-20 size. They are available in stainless steel for all sizes and in brass for some sizes and head styles. Prices range from .20 to .90 cents each depending on vendor, size and head style. A significant advantage of using the stainless steel version is that they can be polished to provide a long lasting high luster appearance. Suppliers of threaded rivets are Restoration Supply Company, Escondido, CA or Material Search Company (MSC) near Pittsburgh, PA.
Examples of threaded rivets. Back row, left to right, 5/16-24 stainless steel round head, 10-32 stainless steel round head, 8-32 polished stainless steel truss head, 8-32 stainless steel truss head, and 8-32 brass round head. Front row, left to right, 6-32 stainless steel truss head, 6-32 stainless steel round head, 4-40 polished stainless steel round head, and 4-40 brass round head.
In this article, we are using the threaded rivets to fasten hardware components onto the trunk. Examples are the trunk handle loops, strap hinges, piano hinges, handles or pulls, latches & clasps, and decorative metal or leather straps. These are the pieces that would be fastened after the exterior of the trunk has been covered, but before the inside lining has been installed. Whether refurbishing an existing trunk or building one from scratch the threaded rivet will aid in fastening these hardware items and give you a more finished look.
The technique presented here is using the threaded rivet with either brass threaded wood inserts or Tee nuts, available from 1) the local hobby shop, 2) directly from Micro Fasteners, or 3) the industrial supplier McMaster-Carr. The wood inserts from Micro Fasteners are small and may suit the thin wood found on trunks better than other versions.
Threaded inserts shown with threaded rivets. Shown are 10-32 inserts on the left and 6-32 inserts on the right.