Riveting is a method of permanently joining metals or other materials, such as leather, plastic and thin plywood. Modern equipment has enabled the home metalworker to place accurately and set strong rivets, which are made of malleable metals such as iron, steel, copper, brass, aluminium and aluminium alloys. The material of the rivet is usually matched with that of the workpiece, although in certain cases different metals can be used together, such as copper rivets in iron work.
A riveted joint can be either loose or tight: for example, the joint which enables the blades to move in a pair of scissors is loose, while metal casings are constructed with tight joints. Rivets, in contrast to nuts and bolts which are bulky, time-consuming to fit, expensive and liable to work loose, are neat, unobtrusive, cheap and quick to fit — and will not work loose except when used as a pivot, when they will eventually wear away.
Types of rivet
There are two basic types of rivet — solid and blind. Blind rivets, require no hammering and may be fixed from one side of the work only. Solid rivets, which can be used for a wide range of jobs, come with several head shapes.
Snap or round head
This type is used for general plate work where it is not important to have a flush finish.
The most common countersunk type is a 90 degree rivet; it is used for a flush finish.
Flat and pan
Used for thin plate work, such as for repair of light metal boxes or wheelbarrows. Bifurcated This type has a split stem, enabling it to be used on softer materials such as leather, plastic and thin plywood.
Types of joint
The placing of rivets depends upon the required strength of the joint and on the final appearance of the work. A well designed joint is made so the rivets are subjected .to shearing loads rather than to tensile (pulling) loads. Rivets may be placed singly in sequence (called line riveting), where there is not much strain on the joint; for jobs which are intended to take a certain amount of strain, a double set of rivets is needed. For even more strength, the rivets should be staggered.
The simplest joint is the single lap joint, where one sheet of metal is laid over another and the two are riveted together; this type is used when no great strength is required and a raised edge is acceptable. When a smooth surface is required, a butt joint with a single lap is necessary; the smoothness of the joint is improved if countersunk rivets are used. Very strong joints require a butt joint with a double lap, where pieces of metal are placed either side of the joint to sandwich it.
Placing a solid rivet
Decide on the design of the joint and where you want to place the rivets. The diameter of the rivet used should be not less than the thickness of one of the pieces of work and not more than three times this thickness; it is often easier when joining two pieces of work to measure the thinnest piece and double this figure for the required rivet diameter.
The spacing of rivets is important to give both a strong joint and a neat appearance to the finished job. The minimum distance between rivet centres must be three times the rivet diameter and the distance between the rivet centre and the edge of the work must be at least one-and-a-half times the rivet diameter.
Rivets come in
various shapes and sizes; the type you use depends on the material you are working and the joint design.
The size of the hole must match the size of the rivet being used. Select a twist drill bit of the right diameter so the rivet can afterwards be pushed firmly into the hole; if the rivet is to be used as a pivot, a slightly looser fit is required.
Mark out the centre of each rivet on the top piece of work by scribing the centre lines and marking the actual hole positions with a centre punch to prevent the drill bit wandering. If you can clamp all the pieces of work together, drill the holes right through all thicknesses then rivet the pieces together, working from opposite corners towards the centre. If you cannot clamp the pieces in this way, you will have to drill all the rivet holes in the top piece first. Mark the pieces so they can be realigned correctly. After drilling.
After drilling, check there is no burr around the edges of the holes; if there is, remove it by lightly countersinking the holes with a countersink bit. This is important because any burr will prevent the pieces of work fitting together properly.
Position the pieces together and clamp them securely in a vice or with a self-grip wrench. Drill one hole through the second piece of work, using the matching hole in the first piece as a guide. Then set the rivet (as described below) before drilling the next hole; follow this sequence throughout the work to ensure all the rivets fit accurately. In this case, ‘work from the centre of the workpiece outwards to avoid distortion and mis- alignment.
If all the holes are drilled before riveting, the work may distort slightly and the rivets will not fit; to correct this you will have to open the holes slightly and this will result in a weaker joint.
Warning Before you make the rivet bite hard on the work, check the pieces are accurately aligned. Although it is nearly always possible to twist the pieces of work around the tight rivet, check alignment before finishing the head. This applies, of course, only to the first rivet. Once the first rivet has been set, you can go on drilling the next hole and setting the next rivet.
A rivet is set by deforming the section which projects through the hole in the work; this has to be carried out neatly and cleanly and finished with a rivet snap. This tool, similar to a flat punch, has a hollow face shaped as the finished rivet head. A rivet set is a similar tool which is used to draw the pieces together before the rivet is set; the set is placed over the rivet shank and hit with a hammer. Both set and snap may be combined in one piece of metal, or they may be separate; if you intend to use a combined tool, you will need an extra piece of hardwood (or another set and snap) to support the head when deforming the shank.
These tools are used with snap head rivets; for flat and countersunk rivets, an anvil or similar flat surface is all that is needed.
Place the pieces of work together and align the holes. Push the rivet through (it does not matter from which side) and place its head in the hollow of the rivet snap which has been clamped upside down in the jaws of a vice. Place the set over the rivet shank and give the set a couple of sharp taps to draw the parts of the joint close together. Remove the set and see how much of the rivet shank now protrudes from the work.
For snap and pan head rivets, the shank should protrude about one and a half times the rivet diameter. For flat and countersunk rivets it should protrude about the same measurement as the diameter of the rivet. If it protrudes more than this you will have to remove the excess. With the size of rivet you are likely to be using, this can be done with a sharp pair of pincers or side cutters; do not use pliers since they will distort the end. With tougher rivets you will have to remove the rivet from the joint and cut it with a hacksaw. If the shank protrudes less, you will have to select a longer rivet and start again. Once you have established the size and length you can cut all the rivets for the job before inserting them.
Once the rivet is cut to length and inserted into the work, you can use the set again to draw the pieces of work up tightly. Keeping the head of the rivet firmly in the snap, use the face of a ball pein hammer to swell the shank of the rivet, then use the ball of the hammer to deform the shank to grip the work. The weight of the hammer must suit the work — for example, a 113gms (4oz) hammer would be suitable for 3mm diameter rivets. Set the rivet gradually, by deforming the rivet to a snap head shape with light taps towards the centre. When the head is nearly shaped, use another rivet snap to finish the work neatly.
If there is surplus metal spreading around the base of the new head, you have cut the rivet slightly on the long side. If you cannot get a neat, rounded appearance to the top, you have probably cut the rivet too short.
Shaping countersunk rivets This type may be finished by filing the head flush with the surface of the surrounding metal; it should be supported on a flat metal block while being shaped and the flat face of the hammer should be used.
Shaping pan head rivets
Finish this type of rivet by forming a snap head and slightly flattening it with the flat face of a hammer.
Most errors are caused by using the wrong technique. For example, if the rivet is too , long, it will bend over when you try to set it. If the hole is drilled slightly too wide, this sometimes gives insufficient support to the rivet and causes it to bend. Occasionally the rivet will split, rather than squash neatly; this is likely to be caused by not hitting it towards the centre. If the pieces of work fail to fit snugly together, this probably indicates burr which has not been removed from the holes; an odd piece of swarf will have the same effect.
When fitting countersunk rivets, be sure the countersink tool you use is suited to the shape of the countersink on the rivet. Failure to do so will result in a weak joint, which in extreme cases will fail easily. When making loose rivets for pivot purposes, you should drill the hole slightly larger than usual; to ensure the rivets do not bulge inside and grip the pieces of work, do not set them too firmly. Apply a little oil to the pieces of work and the rivet before setting; this will help keep the pieces free. In some cases a washer may be placed between them to reduce friction and ensure a loose joint where this is needed.