5.2 Joint Types, Weld Types, and Welding Positions
Key Takeaways
- Five basic joint types: butt, T (tee), corner, lap, and edge — these describe member geometry, not the weld itself
- Groove weld types are square, V, bevel, U, and J, each available in single or double configuration; bevel/J prepare only one member
- CJP welds penetrate the full joint thickness for full base-metal strength; PJP welds penetrate only a specified depth
- Four basic positions: 1 flat, 2 horizontal, 3 vertical, 4 overhead, with G = groove and F = fillet
- Pipe positions: 1G rotated, 2G vertical fixed, 5G horizontal fixed, 6G inclined 45° fixed; 6G is the hardest and qualifies for all positions
Joint vs. Weld — Two Different Words
The exam draws a sharp line between a joint and a weld, and questions exploit candidates who blur them. A joint is the geometry of how two members come together — it exists before any welding. A weld is the deposit that joins them. You apply a weld type (fillet, groove, plug, slot, spot, seam) to a joint type (butt, tee, corner, lap, edge). A T-joint can be welded with a fillet, with a partial-penetration groove, or with both; the joint is still a T-joint regardless of which weld is chosen.
The Five Basic Joint Types
Every welded connection reduces to one of five geometric configurations.
| Joint type | Geometry | Welds commonly used |
|---|---|---|
| Butt joint | Two members in the same plane, edge to edge | Square, V, bevel, U, or J groove |
| T-joint (tee) | One member perpendicular to the face of another (T shape) | Fillet; PJP/CJP groove; combination |
| Corner joint | Two members meeting at ~90° forming an L | Fillet, groove, or combination (open or closed corner) |
| Lap joint | Two members overlapping in parallel planes | Fillet (one or both sides), plug, slot, spot |
| Edge joint | Two parallel members welded along their common edge | Edge weld, square groove |
A frequent trap: a fillet weld is not a joint type — it is a weld type that is most often used on T-joints, lap joints, and corner joints. Likewise a V-groove names a weld used on a butt joint, not the joint itself.
Groove Weld Types
Groove welds are named by the edge preparation cut into the members. Each exists in a single (prepared from one side) or double (prepared from both sides) form.
| Groove type | Edge preparation | Typical use |
|---|---|---|
| Square | No bevel — straight edges, slight gap | Thin material (roughly up to 3/16 in for CJP) |
| Single-V / Double-V | Both edges beveled symmetrically | Most common CJP groove; double-V for thick plate to cut weld volume and balance distortion |
| Single-bevel / Double-bevel | One edge beveled, the other left square | T-joints and unequal-thickness butt joints |
| Single-U / Double-U | Both edges given a J-shaped (radiused) prep | Thick plate — far less weld metal than a V at the same thickness |
| Single-J / Double-J | One edge J-prepared, the other square | T-joints in thick plate |
| Flare-V / Flare-bevel | Formed by rounded surfaces (tubing, bar) | Tube-to-plate and rounded-edge joints |
The key trade-off the exam tests: U- and J-grooves cost more to prepare (machined radius) but remove far less base metal and require far less weld filler than V/bevel grooves of the same thickness, which reduces both cost of consumables and angular distortion on very thick sections.
CJP vs. PJP Groove Welds
Whether a groove weld is complete- or partial-penetration changes its strength, its preparation, and the inspection it triggers.
| Feature | CJP (complete joint penetration) | PJP (partial joint penetration) |
|---|---|---|
| Penetration | Through the full joint thickness | Only to a specified depth |
| Strength | Full base-metal strength across the joint | Reduced; sized to a specific design load |
| Typical use | Moment/seismic connections, tension splices | Shear connections, less-critical joints |
| Back-gouging | Often required to sound metal before the back pass | Not required |
| Volumetric NDE | Frequently RT or UT required | Usually visual (VT) only |
| Relative cost | Higher (more filler, more NDE) | Lower |
A CWI must recognize that a PJP groove has a defined effective throat that is less than the plate thickness, so its allowable load is correspondingly limited — you cannot treat a PJP joint as if it carried full plate strength.
Welding Positions — Plate
Positions are designated by a number for orientation plus a letter for weld type (G for groove, F for fillet).
| Number | Groove | Fillet | Orientation |
|---|---|---|---|
| 1 | 1G | 1F | Flat — face up, gravity assists |
| 2 | 2G | 2F | Horizontal — axis horizontal, face nearly vertical |
| 3 | 3G | 3F | Vertical — weld axis vertical |
| 4 | 4G | 4F | Overhead — welded from below |
Welding Positions — Pipe
| Position | Pipe state | Description |
|---|---|---|
| 1G | Horizontal axis, rotated | Pipe turned so welding stays near flat |
| 2G | Vertical axis, fixed | Pipe upright, weld runs horizontally around |
| 5G | Horizontal axis, fixed | Pipe fixed; welder moves around the circumference (flat→vertical→overhead) |
| 6G | Axis inclined 45°, fixed | Hardest — combines all attitudes continuously |
| 6GR | 6G with a restriction ring | Adds an obstruction ring to simulate restricted access (pipe/T-K-Y) |
6G is the most demanding pipe test because the fixed 45° incline forces the welder through flat, vertical, and overhead progression without repositioning the pipe.
Position Qualification Cascade
A core inspector rule: qualifying in a harder position automatically qualifies a welder for the easier ones (exact ranges follow the governing code — e.g., AWS D1.1 or ASME Section IX — so verify against the applicable code).
| Qualified in | Also qualifies for (typical) |
|---|---|
| 1G / 1F | That position only |
| 2G | 1G and 2G |
| 3G | 1G and 3G |
| 4G | 1G and 4G |
| 3G + 4G | All plate positions (1G–4G) |
| 6G (pipe) | All plate and pipe positions |
Because 6G covers everything, fabricators often qualify welders on a 6G coupon to obtain the broadest single qualification. A CWI verifying a Welder Performance Qualification (WPQ) checks that the position actually tested supports the production work assigned.
Plate vs. Pipe and Common Traps
Two distinctions are reliably tested. First, plate positions stop at 4; pipe adds 5G and 6G — there is no 5G or 6G for plate. Second, students confuse a joint (butt) with a weld (V-groove) and a weld type (fillet) with a position (3F). Keep the four categories — joint geometry, weld type, penetration class (CJP/PJP), and position — mentally separate.
Exam focus: Memorize the five joint types, the groove family (square, V, bevel, U, J × single/double), the CJP-versus-PJP distinction, the 1–4 plate numbering with G/F letters, and the pipe positions — especially that 6G qualifies a welder for all positions. These appear repeatedly across Parts A and C.
Which welding position is the most difficult and qualifies a welder for ALL positions?
What are the five basic joint types?
How does a PJP groove weld differ from a CJP groove weld?