Soft Soldering

This consists of well cleaning the parts to be soldered, applying a suitable flux (for this see p. 188), heating the metal, and applying just sufficient solder to make the joint. Soft soldering must be done with the aid of a soldering iron or bit (see Ch. xvi, f. 16), spirit lamp, gas blowpipe, or heat of some kind to melt the solder. When using a soldering iron or copper bit, as it is sometimes called, it must be well tinned, that is, the iron must be heated, filed clean, rubbed in the flux, and the point covered with solder. It is very often an advantage to tin the parts to be soldered first.

Zinc Chloride For Soft Soldering

Place some pieces of zinc in hydrochloric acid until the acid stops working, then leave it for twenty-four hours. Now strain and filter it, and add 2 oz. of water to the pint of acid.

In Riveting, pieces of metal are joined together with rivets. These are made of various metals and in different shapes, such as half-round or snap head, pan, countersunk, flat, or conical head. A rivet is known by the shape of the head, length of stem under head, diameter of stem, and the metal it is made of.

The method of riveting is as follows : The rivet is selected according to the thickness of the plate to be riveted, the holes for the rivet are then either punched or drilled, the rivet is placed in position and the metal set down with rivet set; sufficient length of rivet is left to project through the plate and form the other head; the end or tail of the rivet should be flat, the tail should be burred over with a light hammer and finished to shape with the aid of a cup tool. For illustrations of rivet set and cup tool see Ch. xvi, f. 21 (27). The distance of one rivet from the other is known as the " pitch," and depends on the nature of the work.

Screwing is joining metals together with screws and should be avoided, as screws are liable to work loose. They are made of iron, brass, bronze, or steel, and have heads of various shapes, half-round heads, countersunk heads, cheese heads, half-round and countersunk combined. All screws used for metal are known as tapped screws or metal-thread screws to distinguish them from screws used for wood. They are made to many standards and in various pitches.

The pitch of a screw is the distance it will move in the direction of its axis in one revolution through a fixed nut. The following are some of the standards : Whitworth, British Association, known as B.A., U.S.A., International Metric, and Bicycle standard. Screws are known by their diameter, standard, shape of head, metal, and length under head, as for example 1/4 in. Whitworth round head, brass, 1 in. underhead. In screwing work together the part that takes the head of the screw has a clearing hole in it, while the other part has to have a tapping hole; this is also known as the core diameter so that it can be threaded. This allows the work to be drawn tightly together. In engineering shops the screws used in machinery for imparting motion are known by their shape such as "square," "buttress," "knuckle," or "acme thread". A set or grub screw is one that has a point and no head, but a saw cut in the screw itself, so that it can be turned with a screw-driver.

Bolting and Wedging is used mostly for fixing together various parts of machines. Bolts are now usually made to the Whitworth standard. The size of the head bears a fixed relation to the diameter of the bolt. There is a large variety in use, such as hexagon, ball, cheese, coach, deck, square, countersunk, etc., the name applies generally to the shape of the head. When an extra long bolt is required a "bolt end " is welded to a length of rod, as this is more convenient. Where there is a lot of vibration " lock nuts " have to be used because ordinary nuts work loose. Of these there are many forms. Wedging, keying, and taper fits are due to factional contact, and in the fixing of nearly all wheels and pulleys this property is utilized as well as in what are known as friction clutches. The system adopted by the Morse and other companies for holding drills of all sizes by means of taper fits and removing them by means of a hand lever is an extremely simple and convenient method in every way.

A Force Fit is where the pin is made very slightly larger than the hole and the two parts are forced together. An example of this is the lathe pulley