It's not very often you get to see some serious boiler work being done the old fashioned way. Pacific Coast Shay #2 under overhaul in the Cass Shop has had its right side firebox sheet replaced from about midway up the side all the way to the bottom. While the sheet was welded to the existing firebox at the top and sides, at the bottom it is riveted to the mudring. Here is the process:
After the rivets are cut to length, they are heated to a bright yellow-orange color in the electric rivet heater. The exact temperature is a bit of trial and error as if the rivet is not hot enough, it won't drive tight and form a good head. Too hot and it will bend when you hammer it into the hole.
While the rivet is being heated the hole is reamed to the proper size.