The forge for heating rivets.

A dolly bar for backing up the old rivet head while the new one is being formed. The dolly is a round iron bar, with one end hollowed out, or cup-shaped, in such a manner as to fit the rivet head. A dolly bar weighs from 15 to 25 pounds. The snap is a hollowed out or cup-shaped hammer used for forging the heads.

The forging hammer is used in hand riveting for upsetting the shank or the red hot rivet and for roughly shaping a new head. Forging hammers usually weigh about five pounds each.

In hand riveting, after the new head has been shaped roughly with the hammer, one of the men, usually the rivet "passer," holds a snap against the rough rivet head while the riveter strikes a few good blows on this snap. This gives the rivet head a spherical form.

A portable air compressor, popularly known as a "gun," is used for riveting in work where machine riveting is required. The shape of the driving hammer is similar to that of the snap. Hence no extra snap is used in machine riveting, the rivet head being formed and made spherical in one operation.

The buster is a blunt-faced hammer having a cutting edge used in shearing off the heads of rivets.

After the head of a defective rivet has been cut off, the balance of the rivet is driven out from the hole by means of a special hammer having a tapering head. This hammer is known as the backing-out punch.

Drift pin is a round piece of steel, slightly tapered, and used for the purpose of drawing pieces together so as to make the holes match preparatory to riveting. Each riveting gang is provided with several drift pins.

A ten-pound sledge hammer is used in straightening out all lugs and splice plates which have been buckled or distorted during shipping or during erection.

The sledge hammer is further used in connection with backing out punches, busters, etc. It is also used with snaps to form cup-shaped rivet heads, and for this reason it is sometimes referred to as the cupping hammer.

The ratchet is a portable hand drill used for making holes. on the job where same have been omitted.

The steamboat ratchet is a turn-buckle device to which cables are attached. It is used for bringing up or pulling columns into a plumb position.

We may add to this list bolts, rivets, washers, fillers, and other minor parts. Each gang is further provided with

several planks for a temporary scaffold and with ropes or chains for fastening their scaffold to the steel work.

Heating Rivets. Good riveting depends to a considerable extent upon the care used in heating. Rivets carelessly heated may burn; this greatly reduces the strength of the rivet. In addition, after the rivet is driven there is no way of telling whether the rivet was burnt or not, as the head may look good while the shank is weak and brittle.

Steel rivets should be heated uniformly to a dull red; the orange color must not be passed. The rivets should be put in place as soon as they reach this temperature and should be worked as quickly as possible. No steel rivet should be worked at a blue heat.

With machine driven rivets the point of the rivet is often heated more than the head. This facilitates the upsetting and flowing of the rivet metal into the hole. When the riveting is done by hand the pressure made to bear upon the rivet through successive blows is considerably smaller. Hence the rivet should be heated uniformly, or the head should be even hotter than the point, otherwise the blows which will upset the rivet and make it fill the hole near the point will have little effect at the other end, and the rivet may not quite fill the hole near the original head.

Iron rivets can be heated without serious injury even to a "wash" or "waste" heat, which is reached when the slag in the metal begins to soak out. Like steel rivets, iron rivets should not be worked at a blue heat.

The following additional rules if followed will contribute towards good riveting:

I. The forge used for heating the rivets should be placed as near to the point of use as practicable.

2. Only a few rivets should be placed in the fire at a time, otherwise some are liable to be left in too long and be burnt.

When the rivets are too long it sometimes happens. that the heater will burn the points on purpose, just to shorten the shank. This is bad practice and should never be allowed.

Re-driving cold rivets injures the heads and should be prohibited.

5. Caulking of rivet heads may injure both the rivet and the plate, and has no excuse in structural work. It is used to make loose rivets appear tight, and should not be permitted. All caulked rivets should be cut out and replaced.

6. Rivets should not be heated several times, nor should they be allowed to remain too long in the forge. In both cases a chemical action of decarbonization and oxidation takes place, and this may injure the rivet when prolonged.

Riveting may be defined as the process of passing a hot rivet through holes in pieces to be united and of forging another head from the projecting shank. It is generally performed by means of air, steam or water power machines, or by hand.

Hand Riveting. In this kind of work the red hot rivet is passed through the hole; it is then held up in place by means of the iron bar called "dolly." This bar is hollowed out at one end in the form of a cup that fits on the rivet head. The dolly is pressed against the rivet head by one of the men, the "holder up," and in the same time the shank is upset by the riveter, who uses a forging hammer with a flat face. The end of the rivet is roughly hammered to a convex point. It is then finished or rounded up, just as the rivet loses its red heat, by placing a "snap," or hollowed steel tool, against the rivet head, and by striking a few blows with a heavy sledge hammer.

Machine riveting is performed by pneumatic, steam or hydraulic riveting machines. It is better and generally cheaper than hand riveting. The practically steady pressure brought by the machine upon the rivet enlarges the shank and squeezes it into the hole, thus thoroughly filling up all the irregularities of the hole, in addition to forming the new head.

Machine driven rivets can be easily distinguished from hand driven rivets. In the first case the rivet head is smooth and more regular, with exception of a slight burr which is often found on the new head and which is due to the die having caught the rivet a little off the centre. Furthermore, machine driven rivets will generally fill up all the irregularities of the hole; when such rivets have to be cut out, after chipping off one head, the balance of the rivet can be pushed out only by means of a pin and hammer, and with great difficulty, while in some instances the rivet will have to be drilled out.

In hand riveting when one head is cut off the shank can be driven out easily, or it will actually drop out. This shows how little hand riveting fills up the irregularities of the hole as compared to machine work. Hand driven rivets also have their heads covered with marks made by the hammer and by the shifting of the snap during forging.

In comparing machine with hand riveting, we may note the following points to the advantage of machine work:

I. In machine riveting the holes are better filled.

2. The rivet is more quickly headed, due to a larger pressure, hence there are, as a rule, less loose rivets than with hand riveting.

3. The work is more uniform and more reliable.

4.

Machine riveting is generally cheaper.

Shop and Field Rivets. Hand riveting done in the shop is generally stronger and better than field riveting done in the same manner. With machine riveting and good supervision there is little difference if any between shop and field work. Some specifications require ten per cent. more field. rivets than shop rivets for the same connection, when driven by machine in the field, and twenty-five per cent. more when driven by hand. Machine rivets are more uniform in strength than hand driven rivets.

There are several causes which tend to make shop riveting better than field work:

I. Parts to be riveted together can be handled more conveniently in the shop.

2. The heating of the rivets is done under more favorable conditions and close to the riveting machine.

Powerful stationary riveting machines are sometimes used. These are definite in their action and results and will generally turn out better work than the portable field riveting machines.

4. The conditions of inspecting the work in the shop are more favorable. This results in better inspection.

5. The stock of rivets kept in the shop is, as a rule, considerably larger than that kept on the job. This avoids the use of short rivets when the rivets of proper length do not arrive on time, as it sometimes happens in field work.

The New York Building Code allows for steel rivets in shear a unit stress of 10,000 pounds per square inch for shop rivets, and only 8,000 pounds per square inch for field rivets. This gives for a 34-inch shop rivet 4418 pounds shearing resistance, while the corresponding value for field work would only be 3534 pounds. With good field riveting, however, 4000 pounds per 3/4-inch rivet in shear may be safely assumed.

Rivets vs. Bolts. Good riveting is better than bolting for the following reasons:

I.

The rivet is forced into the hole and fills it completely. This adds strength in the case of compression members.

2. Riveting furnishes a more rigid connection than bolting. For this consideration riveting is generally used in column splices.

3. The rivet heads upon cooling draw the riveted parts more firmly together.

4. Each rivet filling its hole, moisture cannot work its way into the joint; thus deterioration through rust around a rivet is prevented or delayed.

5. Stresses are likely to be more evenly distributed among a number of rivets than among the same number of bolts. To illustrate this, consider a hanger A (Fig. 11) connected to the web of a channel B by means of two 3/4-inch

bolts. The bolt C was first put in. The second bolt hole in the plate was punched 1/16 of an inch too high. The lower hole was elongated and the bolt D was put in, but as shown in the diagram this bolt takes no load in shear and hence the upper bolt may be overloaded. The only use of bolt D is to slightly prevent the downward motion of the hanger through the friction caused by making this bolt tight. By using rivets, although the lower holes do not match, the upset shanks will completely fill the hole spaces, and both rivets will share more evenly in resisting the shear due to the load supported by the hanger.

It often happens that splices in columns along the walls cannot be conveniently riveted on account of lack of room. In such cases the adjoining wall may sometimes be broken off for one or two feet next to the column splice, thus making riveting possible. Where the adjoining walls are weak, and where breaking into them may render such walls unsafe, as many of the holes as are not accessible for riveting