Craftsman 113.201892 Spécifications télécharger pdf (Page 16)

FLAT

TACK

Flat welding includes all types of joints in which the weld

ishorizontal, and the electrode is fed clown as in the practice

welds of previous pages. The five types of joints in figure 1

can be welded in the flat position.

Butt welds 0n light materlal should be practiced first on

scrap stock. Use 16_gauge mild steel sheet metal (approxi-

mate]y 1/16-inch thick) and 5/64-inch rods with the wetder

set at approximately 30 fo 50 amperes. Buttedges of metal

together and tack;weld approximately every three inches

(fig.::2). (Tack welds are small beads t/4 to 3i8-1nches in

length.) Place bars of scrap iron under ends of the work to

provide an air space above the table. Simply move the rod

in a straight line directly above the edges to be joined.

tf the Weld burns thro_ughin places, reduce the welding cur-

rent or irlcrease the rate_of travel. Some difficulty may be

experienced in starting the arc at these low current settings.

However, once the arc is started, there will be sufficient

heat to make a sourtd weld. After laying a bead, turn the

work over and inspect the Underside which should als0 have

a sinai] uniform bea;€i_:To prevent burning through where

the edges are not butted tightly together, move the rod back

and forth with short quick Strokes in the direction of the

weld to bridge the gap and give the metaf in the crater a

chance to solidify (figL 3).

Butt welds on sheet metal lighter than 18 gauge should

not be attempted by the beginner without the use ofa

back-up strip (fig. 4). This consists of a bar of copper

clamped tightly against the underside of the seam to absorb

the heat of the arc and prevent the weld from burning

through. To assure complete penetration with butt welds

on 8*gauge metal or heavier, a t/t6 to 3/32-inch gap

should be atlowed between them (fig. 5). Insert a wedge or

screwdriver between the plates when tack-weldlng to main-

tain the gap, then turn the piece over, so the tack welds are

on the underside.

Use enough current to melt edges of plates to a depth Of

at least one-half their thickness. Clean off the slag and

inspect it for smoothness, penetration and height of rein-

forcement. A good weld should have a reinforcement slightly

more than flush with the_ surface (fig. 6). Turn the plate

WELDING

SHEET

METAL

BACK-UP

STRIP

Figure 4

Figure 3

6-1#CH

R_KFORCEMENT

Figure 6 _ Figure 5

Figure 7

FIRSTP,ASS

V-WELD

REINFORCING

4-PASSBUTTWELD

rll

Figure 9

_45_y SINGLE-BEVELWELl)

Figure 10

over and weld a simitar bead on the other side (fig. 7). A

higher welding current can be used on this side as there is

no danger of burning through and fusion with the first

bead will be assured.

Although butt welds can be made on steel plates up to

3/8-inch thick, with a 29_ampere machine using 1/4-inch

rod, the same results can be obtained with smaller welders

if eages of plates are beveled (fig. 8). Metal of almost any

thickness can be welded in this manner by depositing a

number of beads, one on _op of the other until the groove

is completely filled. If the plate can be welded from both

sides, always use a double bevel (fig, 9), If only one plate is

beveled, the angle should be at 45 degrees (fig. 10).

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Craftsman 113.201892 Spécifications Page 16

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