Slide 001: Visual Weld Inspection & Quality Criteria

Slide Visual

Slide Overview

This slide teaches students how to visually inspect welds against quality criteria, measure critical weld dimensions, and make accept/reject decisions. Visual inspection is the first — and often only — quality gate for makerspace welding.

Instruction Notes

Visual Inspection Procedure

A systematic approach catches defects that a casual glance misses: 1. Clean the weld: Wire brush to remove slag, spatter, and oxide 2. Inspect with adequate lighting: Use a bright LED flashlight at an angle — shadows reveal defects 3. Check the overall profile: Bead width, height, and symmetry 4. Examine the toes: Where the weld meets the base metal — look for undercut, cold lap, overlap 5. Check for surface porosity: Pits, pinholes, or clusters of pores 6. Check for cracks: Surface cracks at the weld center (hot cracks) or toe (cold cracks) 7. Measure: Use fillet gauge, ruler, or calipers for dimensional checks

Weld Quality Acceptance Criteria

Fillet Welds:

Criteria	Accept	Reject
Leg size	≥ specified minimum (equal legs ±1/16")	1/8"
Undercut	≤ 1/32" depth	>1/32" depth
Porosity	≤ 3 pores per inch, each <3/32" diameter	>3 pores/inch or any >3/32"
Cracks	NONE	Any crack of any size
Overlap/Cold lap	NONE visible	Any visible overlap
Reinforcement	Slight convexity OK	Excessive convexity (>⅛") or concavity

Butt Welds:

Criteria	Accept	Reject
Reinforcement	0 to 1/8" above base metal	>1/8" or any concavity
Undercut	≤ 1/32" depth	>1/32" depth
Porosity	≤ 3 pores per inch	>3 pores/inch
Cracks	NONE	Any crack of any size
Root penetration	Full penetration preferred	Incomplete penetration for structural
Misalignment	≤ 1/16" offset	>1/16" plate offset

Using the Fillet Weld Gauge

The fillet gauge is a simple, essential tool: - Place the gauge against the weld with one leg on the horizontal plate and one on the vertical plate - The gauge measures the ACTUAL leg size - If the weld profile does not contact the gauge at all three points (two legs and the face), the profile is incorrect - Convex profile: Gauge contacts the legs but a gap exists at the face — acceptable up to slight convexity - Concave profile: Gauge contacts the face but gaps at the legs — the weld is undersized (throat is reduced) - Correct profile: Gauge contacts (or nearly contacts) all three points

Weld Profile Shapes

ACCEPTABLE:         ACCEPTABLE:           UNACCEPTABLE:        UNACCEPTABLE:
Flat face           Slight convexity      Excessive convexity  Concave
  ___                 ___                    ___                  ___
 / | \              /  |  \              /    |    \            \  |  /
/__|__\            /___|___\            /_____|_____\            \_|_/
  Equal legs         Equal legs         Excess reinforcement    Reduced throat

Beyond Visual: When to Seek Further Testing

In a makerspace, visual inspection is usually sufficient. However, for structural, pressure, or safety-critical applications, additional NDT (non-destructive testing) should be considered: - Dye penetrant testing (PT): Reveals surface-breaking cracks not visible to the naked eye. Relatively simple and inexpensive - Bend testing: Destructive test that reveals internal defects. Good for qualification - Professional engineering review: Recommended for any load-bearing or structural application

Key Talking Points

1. Visual inspection catches 80% of weld defects — if done systematically
2. Cracks are ALWAYS a reject — no exceptions, no matter how small
3. Undercut and cold lap are the most commonly missed defects by beginners
4. A fillet weld gauge costs $5 and pays for itself by catching undersized welds
5. For structural applications, visual inspection alone is not sufficient

Learning Objectives (Concept Check)

• [ ] Perform a systematic visual weld inspection using a 7-step procedure
• [ ] Measure fillet weld leg size using a fillet gauge
• [ ] Apply acceptance criteria to make pass/fail decisions on 5 weld samples

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Last Updated: 2026-03-19