For more permanent affixing and some detailing, such as steam loco valve gear; rivets are used in lieu of screws. Resembling thread-less screws, their toe end is swaged or peened over to form a flange which secures them. They are frequently used to prevent easy removal and with moving parts, where screws might loosen. In modelrailroading, they are commonly used in assembling or modifying valve gear. Sizes vary from very small to fairly large with round or hexagonal heads. The toe has a hole into which a tool is inserted for flanging. Resembling a center punch or drift pin, the tool is usually tapped with a hammer; but may be pressed. Rivet sources are Bowser, Precision Scale, Mantua, Model Die Casting etc.
Many modelers are intimidated or fail in the first attempts, by using poor methods or tools. First a solid metal surface must be used to backup the rivet head; not wood or plastic. Although a center punch can be used, this frequently splits the flange, possibly causing binding. Around 1950 Penn-Line developed a special swaging tool for these rivets. With a rounded "M" cross sectioned tip, it produces an arc curved flange. It is now marketed by Bowser and is included with their kits.
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RIVET TOOL
RIVET TOOL END
Use is easy. Place the rivet head on the surface with parts to be fastened on the shank. A tiny drop of oil on tip, appears to ease process. Carefully place the tool tip on rivet vertically and tap lightly a few times with a light hammer until flanging starts. Check the play in the assembly. Repeat with lighter taps until play is minimum and alignment is good, but with no binding. Especially at higher speeds, loose, sloppy valve gear can snag piston rods or other obstructions causing jams and damage, even shearing rivets or tearing out holes. This was quite common during the Tyco and AHM eras and has even occurred on brass locos. For non-commercial use, pressing is not recommended for moving parts; since over tightening may occur too easily, without the proper feel.
Larger rivets are useful on other fastening projects including their use as hinges. Probably the easiest and most useful for hobby use are the so-called "pop" rivets, available in various diameters and lengths in both aluminum and steel. These are often called blind, since all riveting can be done from the front. The toe end is flared as the pin is pulled through by the tool. Various insertion tools are also available. The method is particularly useful with sheets and backup washers can be used to prevent pull-through in thinner and softer materials. There is usually no adjustment for the pressure exerted or for length, since the pin snaps off at a predetermined point. By inserting a removable shim between joined pieces and removing after riveting, movement can be attained for hinges etc.
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MORE EXPENSIVE POP RIVETER.
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