Part 12 (2/2)
The lower part of the jaws is rigid while the top is brought down on top of the work, acting as a clah which the current enters the work being handled After the work is clamped between the jaws, the upper set is forced closer to the lower set by a long co turned on with the surfaces of the work in contact, they i point when added pressure on the lever forces theure 43--Operating Parts of a Toledo Spot Welder]
[Illustration: Figure 43a--Method of Testing Electric Welder]
[Illustration: Figure 44--Detail of Water-Cooled Spot Welding Head]
The transformer is carried in the base of the ulator for controlling the voltage for various kinds of work
The clamps are applied by treadles convenient to the foot of the operator
A treadle is provided which instantly releases both jaws upon the completion of the weld One or both of the copper dies h it froive the operator control of the heat, anything fro easily obtained by ure 45--Welding Head of a Water-Cooled Welder]
_Welding_--It is not necessary to give the h when very rusty or covered with scale, the rust and scale should be reood contact of clean metal on the copper dies The cleaner and better the stock, the less current it takes, and there is less wear on the dies The dies should be kept firood contact All bolts and nuts fastening the electrical contacts should be clean and tight at all ti the solution in a wood, stone or lead-lined tank
The solution is allons of water To get the quickest and best results fro point as possible by having a coil of extra heavy lead pipe running inside the tank and carrying live steam A very few minutes in this bath will re water After this washi+ng they should be dipped into a bath of 50 pounds of unslaked liallons of water to neutralize any trace of acid
Cast iron cannot be coh in carbon and silicon, and passes suddenly fro teht iron the te point to avoid injury to the ether with sufficient force to push all burnt h carbon steel can be welded, butto overco applied at one place Good results are hard to obtain when the carbon runs as high as 75 points, and steel of this class can only be handled by an experienced operator If the steel is below 25 points in carbon content, good welds will always be the result To weld high carbon to low carbon steel, the stock should be cla considerably further out froh carbon stock Nickel steel welds readily, the nickel increasing the strength of the weld
Iron and copperthe size of the copper end where it co copper and brass the pressureiron The metal is allowed to actually fuse or melt at the juncture and the pressure must be sufficient to force the burned metal out The current is cut off the instant thedone byof the ether The pressure is applied to the weld by having the sliding jaw ht on the end of an arer volue than for steel and iron The die faces are set apart three times the diameter of the stock for brass and four ties of sheet steel can be welded to heavy gauges or to solid bars of steel by ”spot” welding, which will be described later Galvanized iron can be welded, but the zinc coating will be burned off Sheet steel can be welded to cast iron, but will pull apart, tearing out particles of the iron
Sheet copper and sheet brass h this work requires rades of sheet aluhness left on the surface under the die is not objectionable
_butt Welding_--This is the process which joins the ends of two pieces ofpart of this chapter The ends are in plain sight of the operator at all times and it can easily be seen when the ure 46) It is at this point that the pressure ether in the weld
[Illustration: Figure 46--butt Welder]
The parts are placed in the cla beyond the jaw The ends of the metal touch each other and the current is turned on by means of a switch To raise the ends to the proper heat requires from 3 seconds for 1/4-inch rods to 35 seconds for a 1-1/2-inch bar
Thispractically the saht into contact on each end When such parts are forced together a slight projection will be left in the forree of heat required for any work is found by ulator one way or the other while testing several parts When this setting is right the work can continue as long as the saure 47--Cla Dies of a butt Welder]
Copper, brass, tool steel and all other h teether with sufficient force to force all burned metal from the weld
In case it is desired to make a weld in the form of a capital letter T, it is necessary to heat the part corresponding to the top bar of the T to a bright red, then bring the lower bar to the pre-heated one and again turn on the current, when a weld can be quicklyether at any desired point by a welded spot about the size of a rivet It is done on a spot welder by fusing thesufficient pressure to force the particles of ether The dies are usually placed one above the other so that the work ht down on top of the upper sheet to be welded
One of the dies is usually pointed slightly, the opposing one being left flat The pointed die leaves a slight indentation on one side of the metal, while the other side is left smooth The dies may be reversed so that the outside surface of any work h the dies by a switch which is closed after pressure is applied to the work
There is a limit to the thickness of sheet metal that can be welded by this process because of the fact that the copper rods can only carry a certain quantity of current without beco unduly heated themselves Another reason is that it is difficult topoint without excessive pressure
_Lap welding_ is the process used when two pieces ofheat are forced together by passing through rollers, or under a press, thus leaving the welded joint practically the same thickness as the balance of the work