Craftsman 113.201392 Owner's Manual

UNDERCUT GAS POCKETENTPENETRATIONFigure 11Figure 12Figure 13Run the first pass on beveled plates with a 5/32-inch rodand Jse as high a current as you can handle to obtain asmall bead on the underside. If this is not done, insufficientpenetration will result, as shown in figure 11. Be sure toclean each pass before laying on the next. All beads arelaid by mowng the rod in a straight line with no weavingor side-to-slde movement. On the last or reinforcing pass,a weaving motion must be used to obtain a wide weld thatwill completely cover oreceding beads. For the beginner,the side-to-side movement .with a slight hesitation at eachend) will produce a smooth too without undercut or overlap.Select several practice welds of different thicknesses andcut them into 1-1/2-1nch strips. Clamp each strip in a viseand bend it at the weld (fig. 12). If it breaks through theweld, study it to find the cause of failure.Corner welds are made on light sheet metal by runninga single bead along the top, after tack-welding at three-inch intervals to prevent warping (fig. 13). If numerous gapsare present, a back-up strip may be used. On heaviermetal two passes may be necessary and, if the designpermits, a smaller pass can be laid on the underside.Beveling may be used to advantage on the thicker metals.FILLET WELDSWELDIIBREAKINGTHE WELDFigure 4Figure 6Fillet welds are used to join two pieces of metal with sidesoredges at right angles to each other. The size of such aweld is based on the leg length of the largest isosceles righttriangle that can be inscribed within the cross sectionalarea, as shown by the dotted-llne triangle (fig. 1). Thesize of a fillet weld may also be measured with a squareand ruler, subtracting 1/32-inch from all dimensions under3/16-inch and 1/16-inch from all over 1/4-inch (fig. 2).For example, a 1/4-inch fillet weld should measure 5/16-inch. This will offset any inaccuracy due to the slight radiusat the toe of the weld and allow for concavity of the bead.When cs fillet weld ]s stressed to its maximum capacity,failure will usually occur through the throat section (fig. 3).Therefore, the strength is determined by the throat dimen-sion multiplied by the length of the weld. Finished welds ofthis type should always be at least four times their size inlength; that is, a 1/4-inch fillet weld should never be lessthan one inch long. The direction in which the load is appliedto a weld greatly affects its strength, which can be dearlydemonstrated by breaking the weJd (fig. 4). A ioint soloaded should always be welded on both sides with filletsequat to the plate thickness (fig. 5). If this cannot be done,bevel the plate to assure complete penetration and positionthe work at a 45*degree angle if possible.For practice, tack-weld three pleces of scrap iron togetherto form a cross (fig. 6). Use a 5/32-inch rod with high curren_and hold it as indicated in the front and side views. Movethe rod at a steady even pace along the seam without anyslde-to-side movement and deposit one inch of weld foreach inch of rod melted. The surface contour of a good we_dlr?