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newSchoolWorks.com › VoTechWorks › Building & Construction › Welding › Shielded Metal Arc Welding (SMAW) › Lesson 4
BLD-WELD01-03 · Lesson 4 · 14 clock hours · lab

Striking the Arc and Running Stringer Beads — Flat Position (1G/1F)

Objective. Students strike and maintain a stable arc with E6013 on carbon steel plate and run uniform stringer beads in the flat position with consistent width (±1/8 in.), reinforcement height, and starts/stops free of crater cracks.

Striking the Arc and Running Stringer Beads — Flat Position (1G/1F)

Why This Skill Is Foundational

Every weld you ever make begins with striking an arc. If you cannot start cleanly, maintain a stable arc, and stop without leaving a defect, no other technique matters. The flat position (1G for groove welds, 1F for fillet welds) is the easiest position to weld in and the starting point for all SMAW qualification tests. Master it here and every position that follows gets easier.

Personal Protective Equipment — Put It On Before You Touch Anything

SMAW produces intense ultraviolet and infrared radiation, spatter, fumes, and electrical hazard. Before striking your first arc:

Lockout/tagout (LOTO) applies when you service the machine, change leads, or clear a fault — not during normal welding operation, but know the procedure.

Understanding E6013 Electrodes

The electrode designation tells you everything you need to set up:

For this lesson you will use 3/32 in. electrodes for practice starts and 1/8 in. for the bead-on-plate drill. Store electrodes in a dry, warm place; E6013 is a low-hydrogen-type cellulosic coating and is less sensitive to moisture than E7018, but wet electrodes still cause porosity.

Setting Amperage

A general starting rule for E6013: multiply the electrode diameter in thousandths of an inch by a factor of approximately 1 to 1.1 to get the midpoint amperage in amps. For 1/8 in. (125 thousandths) that gives roughly 90–130 A depending on material thickness, joint position, and machine output. Your instructor will help you dial in the exact setting. Signs you need to adjust:

Always set amperage on the machine before you strike — never adjust live under load on a stick machine unless it is specifically rated for that.

Striking the Arc

Two techniques are used in SMAW:

Scratch start: Drag the electrode tip across the plate like striking a match, then pull back to arc length. Risk: you can accidentally gouge the base metal outside the weld joint. Scratch start is quick to learn but requires control.

Tap start (touch start): Lower the electrode perpendicular to the plate, touch, and immediately lift to arc length. Less chance of stray arc marks, but the electrode can stick if you hesitate.

In both cases, establish arc length quickly. Arc length should approximately equal the diameter of the electrode core wire — for 1/8 in. electrode, that is about 1/8 in. gap between the tip and the puddle. Too long an arc causes porosity, spatter, and a weak, wandering arc. Too short causes stubbing and sticking.

Travel Angle, Work Angle, and Travel Speed

Stopping and Filling the Crater

When you stop, a crater forms at the end of the bead. Craters are stress concentration points and can crack (crater cracks) as the weld cools. To avoid crater cracks: pause briefly at the stop point, allowing the puddle to fill slightly, then break the arc by a quick backstepping motion or a brief backward hesitation before lifting off. Do not just yank the electrode away.

Restarting

When restarting after a stop, strike the arc about 1/2 in. ahead of the crater, then bring the arc back into the crater to reheat it, then continue forward. This ensures fusion through the restart zone and prevents a cold lap.

Self-Inspection

After chipping and wire-brushing each bead, inspect under bright light with a weld gauge and rule:

Record every bead — good and bad — in your weld log. Note the amperage, travel speed impression, and what you would change. That log is evidence of learning and is reviewed during credential preparation.

Key terms10

Arc lengthThe distance between the tip of the electrode core wire and the surface of the weld puddle; for SMAW, the target arc length is approximately equal to the electrode core wire diameter.
Stringer beadA narrow weld bead deposited by moving the electrode in a straight line with little or no side-to-side weaving motion; the fundamental bead type for structural SMAW.
Travel angleThe angle of the electrode measured in the direction of welding travel; for SMAW flat position, a 5–15° drag (trailing) angle pushes the slag behind the arc.
Work angleThe angle of the electrode measured perpendicular to the direction of travel; 90° to the plate for a flat bead-on-plate, 45° between the two members for a flat fillet weld.
CraterThe depression left in the weld pool when the arc is extinguished; must be filled before breaking the arc to prevent crater cracking.
UndercutA groove melted into the base metal at the toe of a weld and left unfilled; a surface discontinuity that reduces the effective throat and can initiate fatigue cracks.
PorosityRounded voids or pores within or on the surface of a weld caused by gas trapped during solidification; common causes include wet electrodes, excessive arc length, and contaminated base metal.
E6013An AWS-classified SMAW electrode with 60 ksi minimum tensile strength, all-position capability, and a titania-based flux coating that produces a soft arc, light slag, and smooth bead appearance; runs on AC or DC either polarity.
Scratch startAn arc-starting technique in which the electrode tip is dragged across the plate surface like striking a match, then quickly lifted to establish arc length.
Fusion at toesComplete bonding between the weld metal and the base metal at the edges (toes) of the bead; lack of fusion at the toes is a rejectable discontinuity under AWS D1.1 visual criteria.

Worked examples4

1. You are using a 1/8 in. (0.125 in.) E6013 electrode. What target arc length should you maintain, expressed in both fractions of an inch and in decimal inches?
  1. Recall the rule: target arc length ≈ electrode core wire diameter.
  2. The core wire diameter of a 1/8 in. E6013 electrode is 1/8 in. (the flux coating surrounds this core, but arc length is measured to the core tip).
  3. Convert to decimal: 1 ÷ 8 = 0.125 in.
Answer: Target arc length ≈ 1/8 in. (0.125 in.).
2. After running a stringer bead, you measure its width at five evenly spaced points and get: 3/8 in., 7/16 in., 1/2 in., 7/16 in., 3/8 in. The target width is 7/16 in. Does this bead meet the ±1/8 in. uniformity requirement?
  1. Convert all measurements to the same denominator (eighths): 3/8 = 3/8, 7/16 = 7/16, 1/2 = 8/16.
  2. Convert to sixteenths for easier comparison: 3/8 = 6/16, 7/16 = 7/16, 1/2 = 8/16. Target = 7/16.
  3. Find the deviation of each measurement from the target (7/16): |6/16 − 7/16| = 1/16 in.; |7/16 − 7/16| = 0; |8/16 − 7/16| = 1/16 in.
  4. The allowable tolerance is ±1/8 in. = ±2/16 in.
  5. Largest deviation = 1/16 in., which is less than 2/16 in.
Answer: Yes. The maximum deviation from target is 1/16 in. (one measurement), which is within the ±1/8 in. (2/16 in.) uniformity requirement. The bead passes.
3. You measure a potential undercut at the toe of your bead with a weld gauge and read 0.038 in. The AWS D1.1 visual acceptance criterion for this exercise is no undercut exceeding 1/32 in. Is this bead acceptable?
  1. Convert the acceptance limit to decimal: 1 ÷ 32 = 0.03125 in.
  2. Compare the measured undercut to the limit: 0.038 in. vs. 0.031 in.
  3. 0.038 in. > 0.031 in., so the measured undercut exceeds the limit.
Answer: No. The undercut of 0.038 in. exceeds the 1/32 in. (0.031 in.) limit. The bead is rejectable and must be repaired or the coupon re-welded.
4. You need to run four parallel stringer beads across a 6 in. wide coupon, with the first bead centered 1/2 in. from the left edge and equal spacing between all beads. What is the center-to-center spacing between beads, and where is the center of each bead measured from the left edge?
  1. The first bead center is at 0.5 in. from the left edge. The last (fourth) bead must also be 1/2 in. from the right edge, so its center is at 6 − 0.5 = 5.5 in. from the left edge.
  2. Total span from first bead center to last bead center: 5.5 − 0.5 = 5.0 in.
  3. Number of spaces between 4 beads: 4 − 1 = 3 spaces.
  4. Spacing = 5.0 ÷ 3 = 1.667 in. ≈ 1-2/3 in. per space.
  5. Bead centers: Bead 1 = 0.5 in.; Bead 2 = 0.5 + 1.667 = 2.167 in. ≈ 2-1/6 in.; Bead 3 = 2.167 + 1.667 = 3.833 in. ≈ 3-5/6 in.; Bead 4 = 5.5 in.
Answer: Center-to-center spacing is approximately 1-2/3 in. (1.67 in.). Bead centers are at approximately 0.5 in., 2.2 in., 3.8 in., and 5.5 in. from the left edge.

The math in this lesson2

Learners convert electrode sizes to decimals, check bead widths against ±1/8 in, and space four beads across a 6 in coupon.
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Brush up in the math halls at newSchoolWorks.com:
In class: Instructor demonstrates scratch-start and tap-start techniques on scrap plate; students observe proper travel angle (5–15° drag), work angle (90° for fillet, 45° for groove), and arc length (approximately equal to electrode diameter), then each student attempts ten start-stop sequences on scrap. · Structured bead-on-plate drill: students run a series of parallel stringer beads across a 3/8 in. carbon steel coupon, aiming for uniform width and no visible porosity; instructor gives real-time amperage and travel-speed coaching. · Self-inspection station: using a weld gauge, scale, and bright light, students measure bead width and height on their own coupons, mark any discontinuities with a paint pen, and record observations on a weld log entry.
Materials: SMAW power source, E6013 electrodes (3/32 in. and 1/8 in.), 3/8 in. A36 carbon steel plate coupons, electrode holder, work clamp, chipping hammer, wire brush, weld gauge, steel rule, paint pen, lab log binder, AWS D1.1 visual acceptance criteria reference card.
Check: Instructor visually inspects three consecutive stringer beads per student against AWS D1.1 visual criteria: acceptable width uniformity, no undercut exceeding 1/32 in., no visible porosity, complete fusion at toes. Students must pass on two of three beads to advance.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

SMAW process knowledge — AWS SENSE L1 / NCCER Welding L1
1. When using the scratch-start technique, what is the primary risk compared to the tap-start technique?
Welding variables and machine setup — AWS SENSE L1 / NCCER Welding L1
2. Which condition most commonly indicates that SMAW amperage is set too low for a 1/8 in. E6013 electrode?
SMAW technique — AWS D1.1 Certified Welder / NCCER Welding L1
3. For a flat bead-on-plate stringer bead with E6013, what travel angle is recommended and why?
Weld inspection and AWS D1.1 visual criteria — AWS D1.1 Certified Welder
4. A student's bead shows a groove at the toe of the weld that is 0.045 in. deep and unfilled. Under the AWS D1.1 visual acceptance criterion used in this lab (no undercut exceeding 1/32 in.), how should this bead be classified?
SMAW technique and discontinuity prevention — AWS SENSE L1 / AWS D1.1 Certified Welder
5. What is the correct procedure for preventing crater cracks when stopping a stringer bead?
Electrode classification and storage — AWS SENSE L1 / NCCER Welding L2
6. E6013 electrodes that have been left uncovered in a humid shop overnight are most likely to cause which weld discontinuity?
Safety and health — NCCER Welding L1 / AWS SENSE L1
7. Which PPE item is specifically required to protect against the ultraviolet and infrared radiation produced by the SMAW arc?
SMAW technique — AWS D1.1 Certified Welder / NCCER Welding L1
8. When restarting a weld after an arc outage on a stringer bead, where should the welder strike the new arc relative to the crater left by the previous stop?
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