Make SMAW Fillet Welds on Lap and T-Joints

A. Finished-Project Specification

Outcome: one SMAW lap-joint coupon and one SMAW T-joint coupon, each with a continuous fillet weld of the approved size and length, complete slag removal, measured leg length and profile within the acceptance standard, and a completed inspection and parameter record. Both coupons are noncritical training pieces and are not represented as certified structural weldments.

B. Component Schedule

Component	Quantity	Material	Finished Size	Preparation
Lap-joint base member	1	Identified mild steel, thickness per approved procedure	Per Chapter 4–6 coupon dimensions	Cleaned to bright metal at overlap and clamp zone
Lap-joint overlapping member	1	Identified mild steel, matching thickness	Per Chapter 4–6 coupon dimensions	Cleaned to bright metal at overlap and clamp zone
T-joint base member	1	Identified mild steel, thickness per approved procedure	Per Chapter 4–6 coupon dimensions	Cleaned to bright metal at joint and clamp zone
T-joint upright member	1	Identified mild steel, matching thickness	Per Chapter 4–6 coupon dimensions	Cleaned to bright metal at joint and clamp zone

C. Material Takeoff

• Base metal: four identified mild-steel coupons carried forward from Chapters 4 through 6 — two for the lap joint, two for the T-joint.
• Electrodes: SMAW electrodes of the classification and diameter specified by the approved procedure, in quantity sufficient for tack welds, both fillet welds, and any approved repair.
• Consumables: none beyond the specified electrodes; no filler wire, shielding gas, or tungsten is used in this chapter.
• Waste allowance: retain sufficient scrap of the same identified material and thickness for the parameter-verification bead required before final welding.

D. Fastener and Hardware Schedule

Not applicable. This chapter joins components by welding; no mechanical fasteners are used.

E. Acceptance Standards

Check	Standard
Lap-joint overlap	Set to the value specified in the coupon record; verified with a rule, stop, or fixture before and after tacking
T-joint angle	Set to the value specified in the coupon record; verified with a square before and after tacking
Tack welds	Sized to hold fit-up without excess; free of cracks, porosity, poor fusion, and misalignment; defective tacks removed and replaced before final welding
Fillet size	Leg length matches the approved procedure within the gauge tolerance stated on the coupon record
Fillet profile	Consistent width and reinforcement, tie-in at both toes, no undercut, overlap, porosity, or slag inclusion visible at the surface
Starts and stops	Full-size weld from start to stop; craters filled; no unfused start or open crater
Slag and cleanliness	Slag fully removed from the fillet and both toes; bead brushed clean
Distortion	Angular distortion recorded and within the tolerance stated on the coupon record

F. Preparation — Joint Review and Surface Preparation

1. Review the joint drawings, coupon dimensions, overlap, orientation, fillet size, length, electrode, polarity, and position. Confirm every value against the coupon record before handling material.
2. Prepare all faying and weld surfaces to clean metal. Confirm cleaning extends beyond the expected weld and work-clamp area.
3. Inspect coupon edges, flatness, dimensions, and joint identification. Reject any coupon outside the tolerance recorded in Chapters 4 through 6.

G. Lap-Joint Fit-Up

1. Set the lap-joint overlap using a rule, stop, or fixture. Confirm the overlap matches the coupon record before clamping.
2. Clamp the lap joint against movement and rocking. Verify both members remain flat on the table under clamping pressure.

H. T-Joint Fit-Up

1. Set the T-joint at the specified angle. Confirm the angle matches the coupon record before tacking.
2. Use a square and fixture to hold the T-joint. Verify the upright member does not shift when the square is removed for arc access.
3. Confirm access for electrode angle and slag removal. Check that the fixture does not block either toe of the intended fillet.

I. Machine Setup and Tack Welding

1. Attach the work clamp to clean sound metal. Position the clamp close to the joint without passing through the fixture.
2. Set the machine and record approved parameters. Record electrode classification, diameter, polarity, and amperage on the coupon traveler.
3. Place tack welds at the approved locations. Follow the balanced sequence specified in the coupon record for each joint.
4. Keep tack welds small enough for control but adequate to hold fit-up. Do not place an oversized tack that will be difficult to incorporate into the final weld.
5. Inspect tacks for cracks, porosity, poor fusion, excessive size, and misalignment. Use the helmet lens and, once cool, direct visual inspection.
6. Remove and replace unacceptable tacks using the approved repair method. Do not weld over a defective tack.
7. Recheck overlap, angle, gap, squareness, and distortion after tacking. Compare against the values recorded in Sections G and H.
8. Plan weld sequence to balance heat and reduce angular distortion. Record the planned sequence for both joints before welding either one.

J. Welding the Lap Joint

1. Position the lap joint for the approved fillet-weld orientation. Confirm flat or horizontal position matches the coupon record.
2. Strike the arc on the approved location. Use the start method demonstrated in Chapter 7.
3. Direct the arc to achieve fusion at both joint members. Observe the puddle at the root and along both surfaces.
4. Maintain the approved work angle and travel angle. Hold the angle values specified in the coupon record throughout the weld.
5. Control arc length and travel speed. Apply the arc-length and travel-speed control demonstrated in Chapters 7 and 8.
6. Observe slag trailing behind the puddle. Confirm the slag pattern matches the approved reference example.
7. Terminate the weld with controlled crater fill. Use the crater-fill method demonstrated in Chapter 8.
8. Allow the joint to cool safely. Mark the coupon hot and place it in the designated cooling zone.
9. Remove slag fully from the fillet and toes. Wear face and eye protection during chipping.
10. Wire-brush the weld. Clean both the bead and adjacent base metal.
11. Inspect the lap-joint fillet for size, length, profile, tie-in, undercut, overlap, porosity, slag, start, and stop. Compare against the acceptance standards in Section E.
12. Measure the fillet using the approved gauge. Record the leg length on the coupon traveler.

K. Welding the T-Joint

1. Repeat the procedure on the T-joint. Apply the same start, angle, arc-length, and travel-speed control used on the lap joint.
2. Maintain equal attention to the vertical and horizontal members. Confirm fusion is achieved at both members throughout the weld.
3. Use the approved sequence if welding both sides. Follow the balanced order recorded in Section I to control distortion.
4. Monitor and record angular distortion. Measure the joint angle after each welded side and record the result.
5. Clean and inspect the completed T-joint. Apply the same slag-removal, brushing, and visual-inspection steps used on the lap joint.

L. Comparison, Defect Analysis, and Repair

1. Compare weld profile with the acceptance example. Place both coupons alongside the approved reference sample.
2. Identify defects and probable causes. Use the symptom-cause-confirmation pattern from the Failure Points section below.
3. Prepare a correction plan before any repair welding. Do not begin grinding or rewelding without a defined method.
4. Complete approved repair only when adequate base material remains. Confirm remaining thickness before excavating a defect.
5. Reinspect repaired areas. Apply the same visual-inspection and measurement steps used on the original weld.
6. Record joint dimensions, tacks, parameters, weld size, defects, repair, and final result. Complete the coupon traveler for both joints.
7. Complete machine shutdown, hot-metal control, and fire watch. Follow the shutdown sequence established in Chapter 1.