electrode from the metal so it can be regripped in the holder.  The welding machine can then be turned back on.  There are two essentially similar methods of striking the arc.  One is the touch or tapping method. When using this method,  the electrode should be held in a vertical position and lowered  until it is an inch or so above the point where the arc is to  be struck. Then, the electrode is lightly tapped on the work  piece and immediately lifted to form an arc approximately  ¼-inch in length.  [Figure 5-29] feed of the electrode. If the rate of advance is too slow, a  wide overlapping bead forms with no fusion at the edges. If  the rate is too fast, the bead is too narrow and has little or no  fusion at the plate. The proper length of the arc cannot be judged by looking at it.  Instead, depend on the sound that the short arc makes. This is a  sharp cracking sound, and it should be heard during the time the  arc is being moved down to and along the surface of the plate. A good weld bead on a flat plate should have the following  characteristics: The second (and usually easier to master) is a scratch or  sweeping method. To strike the arc by the scratch method, the  electrode is held just above the plate at an angle of 20°–25°.  The arc should be struck by sweeping the electrode with a  wrist motion and lightly scratching the plate. The electrode  is then lifted immediately to form an arc.  [Figure 5-30] Either method takes some practice, but with time and  experience, it becomes easy. The key is to raise the electrode  quickly, but only about ¼-inch from the base or the arc is  lost. If it is raised too slowly, the electrode sticks to the plate.  To form a uniform bead, the electrode must be moved along  the plate at a constant speed in addition to the downward  Figure 5-31  provides examples of operator’s technique and  welding machine settings. When advancing the electrode, it should be held at an angle  of about 20° to 25° in the direction of travel moving away  from the finished bead.  [Figure 5-32] If the arc is broken during the welding of a bead and the  electrode is removed quickly, a crater is formed at the point  where the arc ends. This shows the depth of penetration  or fusion that the weld is getting. The crater is formed by  the pressure of the gases from the electrode tip forcing the  weld metal toward the edges of the crater. If the electrode is  removed slowly, the crater is filled.  If you need to restart an arc of an interrupted bead, start  just ahead of the crater of the previous weld bead, as shown  in position 1,  Figure 5-33 . Then, the electrode should be  returned to the back edge of the crater (step 2). From this  point, the weld may be continued by welding right through the  crater and down the line of weld as originally planned (step 3).  Once a bead has been formed, every particle of slag must  be removed from the area of the crater before restarting the  arc. This is accomplished with a pick hammer and wire brush  and prevents the slag from becoming trapped in the weld.  Groove and fillet welds in heavy metals often require the  deposit of a number of beads to complete a weld. It is  important that the beads be deposited in a predetermined  sequence to produce the soundest welds with the best  Figure 5-29.  Touch method of starting an arc. Figure 5-30.  Scratch/sweeping method of starting the arc.  Multiple Pass Welding •  Little or no splatter on the surface of the plate. •  An arc crater in the bead of approximately  1 ⁄ 16 -inch  when the arc has been broken.  •  The bead should be built up slightly, without metal  overlap at the top surface. •  The bead should have a good penetration of  approximately  1 ⁄ 16 -inch into the base metal. Withdraw to long arc $^{1}$/$_{8}$" to $^{3}$/$_{16}$" Long arc immediately after striking Sweeping motion  of electrode 2 0 ° - 2 5 ° 5-26