HINTS ON BRAZING
Page 29
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And a Story of a Little Difficulty with a Steering Gear. Contributed by Our Driver and Mechanic Readers.
THIS WEEK'S prize of 15s. has been awarded to " A.E.," of Newton Heath for his rather long communication embodying hints on brazing, in which
work, he tells us he has had many years of experience. us, first and most im portant thing in connection with a brazing job is the preparation of the part for the operation, and of this preparation that of ensuring cleanliness of the surface's to be joined, is most, essential.
It is possible to 'burn the dirt out, but this is not a good method. The surfaces should be cleaned,, either by filing, scraping, grinding, or by the use of a sandblast. Copper, brass, and bronze parts can be cleaned by dipping theni into A mixture of nitric and sulphuric acids, in the proportion of one part of the former to two of the latter ; this same mixture, by the way, can be used for cleaning the parts aria removing the scale after brazing.
After preparation, the next thing is to decide upon the appropriate spelter, and this is selected according to its fusing point, which must be a little lower than that of the metal parts which are to be brazed; not much lower, as a speller which is too soft does not afford sufficient. strength for the job. Brazing alloys are cemposed of copper, sine, and sometimes silver, compounded
in varying proportions. To raise the fusing point, increase the percentage of copper in the composition ; lower it by adding zinc. . Still rower fusing points may be obtained by the addition of a small percentage of silver. The following table gives the proportions of certain brazing speIters commonly. ernploved, the temperature at which they melt, and the material in the brazing of which they are generally used— Fluxes [or Brazing.
Borax and boric or boracie acid are the two principal fluxes used for this purpose; sometimes the two are used together. In the experience of " A.E." there is practically no difference in the results obtained from either or from the mixture, When using borax it is better to have the borax calcined, as this prevents, it from, swelling and frothing up, so carrying away the brazing alloy .so soon as heat is applied. Calcining may be done by playing the blow-pipe n_pon the borax, when it will swell up. Bub it down when it has cooled.
Method of Procedure.
As a guide to the method of working, the operation of brazing the union nipples cn to a petrol pipe may be described. Before commencing to braze, have ready, close to the work, two shallow trays—one to hold the calcined borax, and the other the brazing mixture, which is the proper speller mixed with about one-third its bulk of borax.
When the bras nipples have been • .
fitted in, clean the copper tubing, filing
it free from sca,le. Knock the nipples tightly on to the tubing and load the joint with a small quantity of borax. Direct the 'blow-pipe flame first. of all on to the nipple, so that the tubing is the last part to heat. So soon as the parts begin to turn a bright red colour apply a little brazing mixture to the joint, using a spatula; which has been prsviol:idly dipped into clean water to prevent the hot borax adhering to it, for the purpose. Work the spatula round the joint until the metal flows freely, then quickly apply a little more brazing metal and borax. So Soon as this has melted the work should be removed from the source of heat and allowed to cool. It is most important that the temperature of the work, should not be allowed to rise much beyond that necessary for melting the spelter, Si otherwise there is a risk of burning it,
Brazing Cast-iron.
Cast-iron is more difficult to braze than other metals because of the presence of free carbon or graphite in the metal. • Commence work by heating to a dull red so as to remove all dirt and grease from the pores of the metal, then clean the surfaces and fasten the parts together in the positions which they are to occupy when brazed. Wherever practicable this fastening must be such that the work may be turned over during the brazing process without disturbing the alignment of the part.
Good results are obtainable from the use of a, mixture of boric acid 16. oz., pulverized chloride of potash 4 oz., and carbonate of iron 3 oz. Mix these thoroughly, and then add 2 lb. of brazing spelter.
A Seized Steering Gear.
" R.M. " of Exeter, having experienced difficulty with his steering gear on a Leyland wagon, decided to investigate, and dismantled the steering gear for the purpose. He sends the accompanying sketch, and points out, in a preliminary paragraph, that the steering rod must be drawn downwards, as a collar on the bottom end prevents upward movement.
The stiffness of his steering, he found, was due to lack of lubrication of the tWO bushes in the column; the upper one, marked A in the sketch, was not only dry but covered with rust from the
steering rod. In his opinion adequate means for the lubrication of these bushes were not provided, and he set about providing them. The upper bush (A) he removed entirely, a,nd cut diagonal grooves in it similar to those which are generally to be found in a crankshaft bearing. Be replaced the bush, and then drilled both column and bush to accommodate a small-sized grease cup, so locating the hole in the bush that the grease was delivered at one of the intersections of the grooves. He then drilled hole in the -column RS indicated. This was to accommodate the nozzle of the grease-gun, which is part of the lorry equipment. Through this hole sufficient oil could be injected to fill the reservoir formed by that portion of the column between the hole aril the top of the bush, and this was enough to last for several weeks. An occasional turn to the grease cup was sufficient for the upper bush.
'The bush A was cupped, no doubt as a means of assisting lubrication. Unfortunately this cup served to collect water, which subsequently ran down the
spindle. He therefore filled in this hollow with solder.