SOME GENERAL HINTS AND TIPS.
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Useful Information on Soldering, Tempering and Hardening.
SCOME VERY useful miscellaneous asIl hints and tips are contained in the following letters, that received from " A.M.D. " of Lanark, being considered worthy of a. special 20s. prize this week.
Be sass:-Drivers who are expected to do running repairs may find a few hints on soldering useful. Soldering is not a difficult job, and only requires a little practice. Any part which has to be soldered must, in the first place, bc• thoroughly cleaned of grease and oxide. Most of the jobs which come the .w.ay of the driver may be executed with the copper bit, and to that I propose to devote most of these hints. When heating the bit, care should he taken non to allow it to reach too high a temperature, and if, by chance, it should be left in the Bunsen flame too long, it should be allowed to cool down before use, as otherwise there is likely to be a considerable waste of solder, which runs straight from the bit if the latter he used while it is too hot. The bit should never be heated to redness, and if it so happens that a hit, already tinned, has been overheated, then the original tinning should be filed off, and the hit cleaned and retinned. This is necessary because the tinned surface, in such circumstances, is apt to form a hard skin which, does not ftmetimi as it should. 'On, account of that same hard skin, the-filing of the bit should he chnie before it is quenched.
" After the bit has been properly cleaned, it should be retinned, and this is effected by heating the bit, dipping it in flex or killed spirits, and then applying the solder to three sides of the bit
only. If the fourth side is tinned the solder will have a tendency to run round the nose of the bit instead of applying itself to the work.
"Assuming thatthe bit has been properly tinned, and is ready for use, the next thing to do is to clean the work. Then apply a thin coating of flux or killed spirits, and finally bring the hit into contact, together with the stick of solder if the area to be operated upon is large enough to demand it.
"I should always be borne in mind that there is no strength in solder itself, and that if the joint is one which is subject to strain, it will be advisable to employ rivets, in addition to the snider, to hold it. In the case of a corner it is generally a good plan to stiffen the work by means of a piece of sheet brass. • " Cast iron is tot easily soldered, and where the material to be worked is of cemsiderable bulk, a blowlaxnp will be necessary in order to raise it to the re. quisite temperature for soldering, the success of which is very largely dependent upon the work being carried out, from begirming to end, at the right working heat. If the material is not thoroughly heated, it will cool, and cool the bit, before the solder has time to run arid make the joint.
" As a matter of fact, with many castiron jobe, it is better to dispense with the bit altogether, and make use of the stick of solder direct. In such a case, heat the material, and then apply the spirits with a piece of clean rag, at the same time rubbing the solder all over the place to be treated. Once a skin of solder has been formed upon the surface, that is to say When the surface has been tinned,' heat again, and make use of the bit for the subsequent operation.
"Soldering — 'killed ' — spirits are Made by dissolving zinc clippings in hydrochlaric acid (sometimes called mudatic acid, or, more commonly, spirits of salts), adding the zinc until no more will dissolve. It should always be borne in mind that the spirits are corrosive, and that the work must always be cleaned most carefully after the kilo is done.'
"Next to soldering, the most interesting job is that of tempering and harden ing. The following few hints on this subject may of use to.thoee drivers
and mechanies who occasionally have such jobs to do, but have not the services of a smith on which they may draw.
In tempering tools, the part which has to be tempered must be carefully cleaned. As hardening depends so much on temperature, and as the temperature of a piece of steel is indicated by its colour, it is important that dirt or rust should nat be present to interfere with proper observation of the colour of the part while it is cooling clown to that temperature at which, for correct hardening or tempering, it must he plunged into water, or oil, as the case may be.
"When the tool shows-a pale blue col. our it is too soft for any work. For the initial hardening it should he heated to a cherry red. A screwdriver should be heated to a dark blue. Chisels must be tempered at different heats according to the .tork for which they are required ; for example, when needed for wrought iron dark purple is correct, but for east iron and steel a light purple is better. Twist drills must be quenched when they are coloured yellaw, with a purple tinge. Reamers must be a broavnish yellow, chasing tools and taps a dark straw yellow, and screw-cutting otes a shade darker than this. Scraping tools for, brass, on the other hand, must be a pale straw yellow. Tools are usually quenched in water, into which they are plunged so soon as the right, colour showson the metal
-"To temper a spring, heat it to a dull red heat all over and then quench in oil Afterwards burn the .oil off in a flame and withdraw the spring so soon as all the oil is burnt.
urface or case hardening is a different process altogether, the surface only of the material, to a. depth of about -Ain., being hardened. The material must be heated to a bright cherry red, and then laid in contact with prussiate of potash, hone duet, or horn shavings. These substances are rich in carbon, which the heated part absorbs. After this process has been repeated three or four times, the part shoaild be heated yet once again and quenched quickly in water.
"When quenching a tool, the following rules should be observed :—H the length is greater than the diameter, the tool -should be plunged into the water straight down, that is to say in the direction of its length, otherwise it may be warped in the quenching. Nuts may have their outer surface hardened in the manner described above, and, so treated, will be foundto withstand repeated applications of the-spanner much better than ordinarily. In hardening nuts, however, take caye , that the threaded part is filled in with clay.
" It is, of course, most important that the -correct heat be reached before quenching, ru otherwise treating any of the parts in question. Bright red or white heat is always too great, and if any delicate part be broughtup to the temperature which is indicated by that colour, then it will most likely be spoilt by being burnt. When the process of hardening or tempering is completed, the part should be thoroughly cleaned by placing a strip of emery on thd face of a thin flat file and removing from the treated part any roughness which may remain from contact with the hardening material which has been used. •
" It may be as well to mention that eopper, is hardened in precisely the opposite way from that, used for steel. " HIT,.," of Highgate, also sends us a tip aboet solder. He says that lead may frequently be used in place of ordinary hard solder, and has the advantage that it does not need to be heated to such a high temperature as the ordinary material. On one occasion, he tells us, he soldered a puncture in a carburetter float, using only a candle flame to provide the necessary beat. An alloy which he occasionally uses is made from lead and quicksilver in the proportions of one to nine. Melt the lead and add the quicksilver, then Dour into a trough made of brass foil so that a long stick forms.