Weld toe: meaning and how to check it

Use this diagram

Copy this HTML to show the diagram with a credit link<img src="https://filletgauge.com/charts/filletgauge/weld-toe.svg" alt="A V-groove butt weld with dots at both edges of its crown labeled toe, and a convex fillet at a T-joint with one toe on the base plate and one on the stem" width="100%"><p><a href="https://filletgauge.com/guides/weld-toe?utm_source=embed&amp;utm_medium=referral&amp;utm_campaign=figure_embed&amp;utm_content=weld-toe.svg">Each toe is where the face meets the base metal. by Fillet Gauge</a></p>

How to find and check the toes

1. Follow the face to its edge. Start on the weld face and move outward until you're on base metal. The line you cross is the toe.
2. On a fillet, find both. One toe sits on each member. On a T-joint that means one on the base plate and one up the stem. Each fillet weld leg is measured from the root out to its toe.
3. Look at the transition. A smooth blend from weld into plate is what you want. A sharp notch, a groove melted into the plate, or weld metal rolled over the plate without fusing are all toe problems.
4. Check with a gauge. Undercut depth is read at the toe with a V-WAC style gauge or a similar depth tool.

Common mix-ups

• Toe versus edge. The toe is a line on the finished weld. The edge of the groove preparation is under the weld and gone after welding.
• Undercut versus overlap. Both live at the toe. Undercut is a groove in the base metal left unfilled; overlap is weld metal lying on the plate surface without fusing. One removes metal, the other adds metal that isn't bonded.
• Toe angle. A tall, steep crown makes a sharp angle at the toe. That's why excess weld reinforcement and excess convexity are judged by profile, not just by height.
• Fatigue. On parts that see repeated loading, cracks tend to start at the toe because it's the sharpest change in shape. Toe grinding and profile control exist for that reason.

The weld toe on the CWI exam

The toe is a core term in Definitions and Terminology, at least 12% of the closed-book Part A, and it comes back in Visual Examination, at least 10% of Part A, whenever a discontinuity is described by where it sits.

On Part B, undercut and overlap at the toe are measured and called on the replicas. Welding Inspection and Discontinuities is at least 34% of the practical, and toe readings are some of the most common measurements in it.

On a D1.1 Part C, toe conditions such as undercut fall under the visual acceptance criteria in Clause 8. Look up the limits in your own copy; none are given here.

Practice it

The weld gauge reading trainer gives you undercut and overlap cases drawn at the toe, and asks you to read the gauge and make a call. The whole family of weld-part terms sits in the welding terms glossary.

Know the parts of a weld? Check the rest of Part A

Take the free 10-question check. It's weighted to the Part A outline, scored by domain and needs no signup, so you see which domain costs you the most points. The Part A course then gives you a lesson on every exam subject, two full-length timed practice exams, and a worked explanation with every answer.

Sources

Show the list

• AWS bookstore, terminology and symbols listing, American Welding Society. Retrieved 20 Oct 2026.
• CWI Part A Fundamentals Examination Information, American Welding Society, Rev. 03.01.2024. Retrieved 20 Oct 2026.
• AWS B5.1:2025, Specification for the Qualification of Welding Inspectors, American Welding Society, Tables 5.1 and 8.1. Retrieved 20 Oct 2026.