The art of making wiped solder joints is acquired only by experience, and written instructions concerning the subject amount to but little. To be able to make the various forms of wiped joints in a perfect manner is the ambition of the young plumber, and it may be said that comparatively few actually reach a high standard in this branch of the work.
In modern plumbing construction the use of lead and solder is very limited, for the reason that the employment of lead for nearly all purposes in plumbing construction has been replaced by the use of other materials.
Indeed, the use of lead is now very largely confined to short lengths of lead waste and vent pipe, and in a great deal of work no lead whatever is used. This is a great change from the conditions that obtained years ago, when the older plumbers of to-day were working at their trade. In those days, all traps, bends, etc., and even soil pipe, were made of lead, and made by the workman himself. In addition, lead was used entirely for the lining of tanks; lead safes were extensively used, and a large amount of ornamental lead work was constructed. It is not strange, therefore, that skill in the manipulation of lead and solder has declined greatly in recent years, and indeed, it may be said that the skill in this line of work formerly required is no longer a necessity.
The reason for the use of the wiped joint is that this form of joint is stronger than other forms, and presents a better appearance.
The wiped joint should be symmetrical, both to secure uniform strength and neat appearance. The two illustrations shown in Fig. 9, show poorly constructed joints.
Wiped joints are made in a variety of shapes and sizes. In some sections of the country, it is customary to wipe a short, thick joint, while in others, long, thin joints are made. Joints excessively long or excessively short are unsatisfactory. If solder is to be economized, it is better to make the saving in length, rather than in thickness, for a short, thick joint has greater strength than a long, slender joint. The strength of a wiped joint depends not only upon the amount of solder used, but upon the quality of the solder. A joint may be well wiped and of symmetrical shape, and still be a poor joint, owing to its being porous. When porous, the joint will "sweat" as it is termed, that is, drops of water will ooze through the solder. This is caused by the poor condition of the solder, due usually to a lack of the proper amount of tin. Solder when made of the proper proportions of lead and tin is much stronger than the lead, and it is the tin that gives the solder its strength by cementing the mass of metal together.
Fig. 9. - Poorly Shaped Wiped Joints.
In Fig. 10, several kinds of wiped joints are shown, also the method of preparing the lead pipes which are to be joined together by the joint.
The simplest joint is the round joint of Nos. 1 and 2. This joint may be wiped upright or underhand, that is, horizontally.
Nos. 1 and 2 in Fig. 10, show two different methods of preparing the pipe. In No. 1 the female end of the pipe is prepared with the tap borer or the rasp. If the latter is used, care should be exercised to prevent the inside of the pipe from being roughed up by the striking of the end of the rasp against it. The male end is then rasped off to fit the female end.
In the case of No. 2, which is preferable to No. 1, the female end is flared out with the turn pin, the inside surface being shaved to give a clean, bright surface. It is essential that the two surfaces that fit together should be bright and free from all tarnishing, in order that the solder may adhere and make a perfect joint between the two pipes.
Fig. 10. - Wiped Joints.
The next step is to shave off the surface of each pipe lengthwise, as far as the joint is to extend, this being done with the shave hook.
All burrs or rough edges should be made smooth. A very important feature is to join the two pipes together in such a way that anything flowing through the pipe when it is in use, shall have the least possible opportunity to catch on the inside or male end.
Thus, in Nos. 1 and 2, any lint or other material in the waste, would have less opportunity to catch at A A and B B if flowing in the direction of the arrows, than if flowing in an opposite direction. In making a perfect joint, the solder should be able to penetrate into the joint between the two pipes, but it should not be allowed to penetrate into the interior of the pipe, where it would form in sharp points which would catch and hold matter flowing through the pipe.
Before the joint is ready to be wiped, the surface of the pipe beyond the joint and on both sides of it, should be protected, so that the solder may not adhere to it at any point beyond the joint. This may be done in several ways. The universal, old-style method was by means of soil, the soil being allowed to remain on the pipe after the work was completed, it being considered ornamental. The use of soil is practiced to quite an extent even now, but its use is decreasing. Soil is made of lampblack and glue, and when properly made, should stand the following test: Apply the soil to a piece of lead pipe, and allow it to dry. If the lampblack rubs off, it shows too much of this material. If, when the pipe is bent, the soil cracks and breaks off, it shows too large an amount of glue. It may be tempered to stand both these tests.
Fig. 11 shows a round joint and a branch joint set up, ready for wiping, with soil applied.
Another method of preventing the adhesion of solder outside the joint, is by means of paper pasted onto the pipe. The paper covers the same surfaces that are shown covered with soil in Fig. 11. In the case of the round joint it is a simple matter to put on the papers, but in branch joints and other joints of irregular shape, it is often a difficult matter to cut the paper in the proper shape. Another disadvantage in the use of this method is that sometimes the paper is poorly pasted, or poor paste is used, and the solder works under and sticks.