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Rivets are used when two materials, especially metals, are to be joined permanently, that is, when there will never be the need to take apart the assembly and then reassemble it.

Kinds of rivets

Rivets are made in a great variety of heads, shanks, and metals. Some large steel rivets must be applied in a red-hot state when used to hold together the great steel girders of buildings and bridges and the heavy steel plates of ship hulls. Others, extremely small in size, are used in such fine industries as jewelry-making and watch manufacturing.

We shall consider here only rivets used for ordinary sheet-metal work, as in the aviation and radio industries.

Rivets are described according to:

1. Shank, as solid, tubular, or special type such as Riv-Nut
2. Metals, as topper, aluminurn alloy, soft steel, and the like
3. Shape of head
4. Diameter of shank
5. Length of shank.

Solid shank rivets are the type commonly used for most purposes in sheetmetal work.

• Countersunk rivets are useful where streamlining is needed, as in air-planes. The countersinking is done as for bolts and screws. It permits the head of the rivet to be placed flush with the surf ace of the metal.
• Roundhead rivets are used where a strong union is required but where the protrusion of the head causes no concern.
• Flathead rivets are used in such constructions as fuel tanks.
• Brazier-head rivets are used on certain external surfaces of aircraft and for patching.
• Tubular shank rivets are shallow drilled for metals. For soft materials, like leather, they are deep drilled.
• Riv-Nuts are made for use on surf aces that can be reached on only one side, as in certain places on the fuselage of a plane. Note that in ordinary riveting the mechanic must be able to reach both sides of the metal at one time; holding the rivet in place on one side and upsetting it on the other side. Riv-Nuts are used for attaching de-icer boots on a plane and for similar purposes.
• Explosive rivets are also made for places that can be reached only on one side or where there is insufficient room for the swing of the hammer in upsetting and heading. They look like solid shank rivets, but near the end of the shank they contain an explosive charge. The rivet head is held in place and when the charge explodes, it swells out the end of the rivet as if it were upset by a hammer.

Sizes of rivets

Tinners' rivets are made of soft steel, coated with tin to prevent rusting. Sizes are given in ounces or pounds according to the weight of 1000 of the rivets. Thus, they may be 8 ounces (very small), 1 pound, or 1 1/2 pounds in size. Other kinds of soft-steel 'rivets are sized by diameter and length of shank, as 1/8” x 1/2" or 1/8” x 3/4" .

The length of all rivets except the flathead type is measured from the underside of the head to the end of the shank. The length of flathead rivets is over-all, that is, from the top of the head to the end of the shank.

Driving rivets

First properly locate and punch or drill the rivet holes in the work. Decide on the proper type and size of rivet to be used. The length should equal the thickness of the stock plus 1 1/2 times the diameter of the rivet. The diameter of the rivet should be just sufficient to fit the hole as perfectly as possible. If the rivet is not long enough, too little metal will protrude for driving. As a result, just a little strain will be enough to separate the metals that were intended to be held securely and permanently in place by the rivet.

A rivet is secured in place by upsetting the end of the shank, that is, by mushrooming or spreading out the end with a hammer. If too much of the shank protrudes the rivet will bend, a tight clamp will not be made, or both may happen.

Insert the rivet in the hole so that the head is under the work resting on a solid surface such as an anvil, stake, or riveting blank. Hold the pieces of metal together firmly. If this is not done after the rivet is upset and headed, it may be found that the two metals have separated just at the spot where they were supposed to be kept in close contact by the rivet.

With a peen hammer, strike straight down on the rivet with a heavy blow. Then strike three or four times more with heavy blows. This will expand the shank of the rivet so that it completely fills the hole. Form a head by striking the outer edges of the upset rivet end with glancing blows, gradually circling the rivet. The peen hall or the face of the hammer may be used for this.

If the head must be formed to shape, a rivet header, or rivet set, should be used. Before peening the rivet end, the hole in the bottom of the rivet header is sometimes placed over the rivet and the header is struck with the hammer to force the pieces of metal together.

When riveting leather and similar soft materials, flathead copper rivets should be used. Burs should be placed over the end of these rivets before heading them.

A special tool is needed with Riv-Nuts. The tool is screwed on to the threaded part of the Riv-Nut; then compression is applied. This causes the Riv-Nut to bulge directly under the head. A key fitting into a slot cut into the metal on the underside of the head prevents the Riv-Nut from turning.

Removing rivets

Though rivets are used for permanent fastenings, sometimes they must be removed, as for repairs. Several methods are used.

1. Place a center-punch mark in the exact center of the head of the rivet. With a drill of exactly the same diameter as the rivet, drill a hole completely through the rivet. If done accurately the shank of the rivet will have been cut away leaving just two thin rings on top and bottom. They can easily be brushed off.
2. If the parts riveted together are made of steel, and are more than a quarter of an inch thick, the shearing method may be used. The chisel is held with one bevel pressed firmly against the surf ace of the plate and the edge of the chisel touching the rim of the rivet head. When the chisel is struck sharply it forces the head of the rivet along the plate in the direction of the blow. The chisel acts like one blade of a shears; the plate itself plays the part of the other blade. A few sharp blows should shear off the head. Warning: When a rivet is removed in this way, goggles must be worn. Care should be taken to see that no one passes or stands in the possible path of the rivet. Have your teacher check conditions before you strike the chisel. A flying rivet head can cause serious injury within a range of thirty feet.
3. A safer method is to hold the chisel as described in instructions under method (2) and with a sharp blow curl up one edge of the rivet head. Then repeat the operation from a point opposite. In the space provided by the curling up of the head insert the jaws of a pair of end- or side-cutting nippers. Closing the nippers will snip off the head of the rivet. This is a safe and quick method. This method is not approved for use with soft metals, as in the airplane industry, because of the possible damage to the work.
4. File off the head of the rivet, taking care not to mar the surrounding metal.

In all three cases, after the head of the rivet has been removed, drive the rivet out with a tool called a driving punch. This tool resembles a center punch but has no point on its end. Instead, it is ground flat. The diameter of this flat end should be slightly less than the diameter of the rivet. Never use a center punch because the point will spread the shank of the rivet and lock it in the hole.

In double-countersunk rivets, both head and upset ends are flush with the surface. These rivets may be removed by cutting a slot similar to the slot in a screw. This slot may be cut in either the head or the upset end. To cut this slot, use a small cape chisel. The edge of this cape chisel should be as wide as or a little wider than the diameter of the shank of the rivet.

Start the cut at the approximate center of the rivet and cut toward one edge. Then, using the same starting point, make a cut reaching to the opposite edge. There will now be a high point in the slot, at the center. Chip this out and then deepen the slot until the shank of the rivet is reached. When this occurs what is left of the head will f all off. By using the drift punch the rivet may now be removed.

When a rivet works loose it may indicate faulty workmanship, material or design. Try to find the cause. Possibly some other part has loosened and overloaded the rivet. It is good practice to replace a loose rivet, and safety regulations generally require that this be done. But if necessary, a rivet can be tightened by repeating the process used in installing it. A center punch may be used to spread it and cause its shank to fill the hole if the sections it holds together are thin. Remember that for a good job the rivet should be replaced, because the treatment used in retightening may so weaken it that it cannot be relied upon.