Hot riveting of historic metals or the replication of historic metal sections such as truss bridge components using the hot riveting process preserves an important historic manufacturing process. Many historic iron and steel structures were originally manufactured using hot riveting, both in the shop and in the field. Hot riveting is often referred to as a “lost art,” and while riveting is rarely used in building construction today it is a viable method being used in the restoration of historic metals and the replication of historic metal structures. Riveting was successfully used during the restoration of five historic metal truss bridges for the Calhoun County Historic Bridge Park in Michigan, and Dr. James Cooper, Professor Emeritus of History DePauw University, cited many examples of Indiana restoration work using riveting in his Workshop presentation “Beauty and Efficiency in Historic Hoosier Highway Truss Bridges.” Specific examples of restoration involving hot riveting, along with the hands-on demonstrations of hot riveting during the Workshop, addressed the lack of knowledge about this process among many engineers and historic preservationists and showed that hot riveting is a viable method for preserving important historic features of iron and steel structures and, indeed, the historic manufacturing process.
Cost is often used as a primary reason for rejecting the replacement of rivets with rivets in the preservation of historic metal structures. Another argument against riveting is that it is difficult to locate sources of steel rivets, riveting equipment, and experienced craftsmen. Original rivets are often replaced with high strength bolts or with button head tension control bolts. In fact, for some projects, riveting can be done at reasonable cost with readily available materials and with properly trained workers.
Although qualified riveters may be few and far between, workers with heavy industrial experience can easily be trained to rivet in order to carry out such work on a historic preservation project. This is a message that was conveyed to participants in the project’s March 2010 Workshop and also demonstrated in the preparations that led up to the Workshop. None of the welding staff at Lansing Community College, except for the project’s PI Vern Mesler, had had any prior experience with heating rivets and driving rivets with a rivet hammer. During the months leading up to the Workshop, training sessions were scheduled for several members of the welding staff and resulted in these craftsmen becoming very proficient in the use of the rivet hammer and the proper procedures for the critical task of heating rivets in a forge.
Availability of rivet equipment and steel rivets was also addressed at the Workshop, both in presentations and in Michigan Pneumatic Tool’s extensive display of rivet equipment and rivets of various sizes and shapes. Steel rivets can still be purchased today and in most sizes that were available years ago.
The cost of riveting, often cited as a barrier to the use of hot riveting in historic preservation projects, was a topic included in the Workshop to make participants aware of two main aspects to be taken into consideration: the cost of hot riveting may not be as great as is often thought, and there are hidden costs in using other methods (for example, replacing rivets with button head tension control bolts) that are often not part of the discussion. Specialized wrenches for installation are required for tension control bolts, and tension control bolts are more expensive than regular structural bolts.
To replace historic rivets with rivets or with bolts is a serious discussion among engineers and preservationists, and not having accurate information to make informed decisions for using the hot riveting process prevents the process from being specified in restoration or rehabilitation of historic metal structures. The March 2010 Workshop was designed in part to address this issue, to give engineers and preservationists an opportunity to see the process in use and experience it through a hands-on activity. [View video: The Hot Riveting process with a field rivet hammer]