Welding blueprints can look like a foreign language, filled with lines, arrows, and cryptic symbols that hold critical information. Among them, the flare-bevel weld symbol is one that trips up even experienced fabricators. Whether you’re reading structural drawings, performing mobile welding repairs in Ontario, or studying for CWB certification, understanding this symbol ensures precision, safety, and full compliance with CSA W59 and AWS D1.1 astandards.
This complete guide breaks down everything you need to know about the flare-bevel weld symbol — from how to identify it on a weld symbol blueprint, to sizing, effective throat calculation, and how it compares to other groove welds.
What Is a Flare-Bevel Weld? (Definition & Joint Type)
A flare-bevel groove weld joins two members where one edge is curved (rounded) and the other is flat. The curved surface creates a natural groove that is then filled with weld metal, forming a strong, clean joint without requiring any additional edge preparation like grinding or machining.
Unlike standard V-grooves or bevel grooves that require machined edges, the flare-bevel joint gets its shape from the natural curve of the base material — making it especially efficient for:
- Pipe-to-plate connections
- Round or square tube welded to a flat surface
- Sheet metal with bent or curved edges
- Round bar stock joined to flat plates
- Automotive structural panels and chassis joints
Key Characteristics of a Flare-Bevel Weld:
- One curved member + one flat member form the joint
- No pre-machining of the curved edge required
- Ideal for thin to medium-gauge metals
- Produces a smooth, visually clean weld profile
- Requires precise fit-up and consistent edge contact for full fusion
In Ontario, flare-bevel welds are regularly found in:
- Structural fabrication (curved beams, supports, crossmembers)
- Automotive repair and manufacturing
- HVAC and tubing assemblies
- Mobile welding repairs on construction sites and industrial equipment
How to Read the Flare-Bevel Weld Symbol on a Blueprint
Canadian weld symbols follow CWB (Canadian Welding Bureau) and CSA W59 standards, which are closely aligned with AWS A2.4. The flare-bevel weld symbol specifies where, how deep, and how long the weld should be made at the curved-to-flat joint.
Components of the Flare-Bevel Weld Symbol
|
Symbol Component |
What It Represents |
Example |
|
Reference Line |
Horizontal baseline — all weld info attaches to this line |
──────── |
|
Arrow Line |
Points to the exact joint requiring the weld |
↙ to joint |
|
Flare-Bevel Symbol |
Curved arc shape placed on the reference line — looks like )⎺ |
)⎺ |
|
Weld Size / Depth |
Number to the left of the symbol — indicates groove depth |
3 (= 3 mm depth) |
|
Weld Length |
Number to the right of the symbol — total weld run length |
50 (= 50 mm long) |
|
Tail (Optional) |
Specifies welding process, WPS, or special instructions |
GTAW, SMAW, etc. |
|
Contour Symbol |
Flat, convex, or concave finish required after welding |
Flat line = flush grind |
Arrow Side vs. Other Side — A Critical Distinction
- Locate the Arrow: Follow it to the exact joint location on the drawing.
- Check the Reference Line: This is the horizontal line carrying all weld specifications.
- Identify the Flare-Bevel Symbol: Look for the curved arc shape )⎺ on the reference line.
- Read the Size Dimension: The number to the left of the symbol is the groove depth or weld size.
- Read the Length: The number to the right indicates how long the weld should run.
- Check the Tail: Any process, WPS number, or special instruction appears here.
- Cross-Reference the WPS: Always verify against your CWB-approved Welding Procedure Specification before welding.
The position of the flare-bevel symbol on the reference line tells you which side of the joint to weld:
- Below the reference line= weld on the arrow side (the side the arrow points to). This is the most common placement on fabrication drawings.
- Above the reference line= weld on the other side (opposite to where the arrow points). Rotate your perspective 180° from the arrow direction to locate the correct joint face.
- Symbols on both sides of the reference line= double flare-bevel; weld both sides of the joint. Each symbol may carry its own independent size dimension and contour specification.
Step-by-Step: Reading a Flare-Bevel Symbol on a Drawing
- Locate the Arrow: Follow it to the exact joint location on the drawing.
- Check the Reference Line: This is the horizontal line carrying all weld specifications.
- Identify the Flare-Bevel Symbol: Look for the curved arc shape )⎺ on the reference line.
- Read the Size Dimension: The number to the left of the symbol is the groove depth or weld size.
- Read the Length: The number to the right indicates how long the weld should run.
- Check the Tail: Any process, WPS number, or special instruction appears here.
- Cross-Reference the WPS: Always verify against your CWB-approved Welding Procedure Specification before welding.
Pro Tip: Always cross-reference the flare-bevel symbol with the CWB-approved Welding Procedure Specification (WPS) for the project. For mobile welding assignments in Ontario, carry a portable copy of the WPS and relevant CSA W59 sections.
Flare-Bevel Weld Size & Effective Throat — How to Calculate
One of the most critical — and most frequently misunderstood — aspects of the flare-bevel weld is calculating the effective throat. This directly affects structural load capacity and must be done correctly for code compliance.
Effective Throat Formula (AWS D1.1 / CSA W59)
For a flare-bevel groove weld, the standard effective throat is calculated as:
|
Condition |
Effective Throat Formula |
Notes |
|
Standard (not filled flush) |
5/16 × R |
R = radius of the curved member |
|
Filled flush (reinforced to surface) |
5/8 × R |
Verified by inspection; larger effective throat |
|
GMAW / FCAW processes |
May use 5/8 × R even unflushed |
Per AWS D1.1 Table 2.1 prequalified conditions |
For example, if a round tube has a radius of 16 mm, the standard effective throat = 5/16 × 16 = 5 mm. This is the value used in structural capacity calculations, not the full visible depth of the groove.
Why Effective Throat Matters
- It determines the weld’s load-carrying capacity
- Inspectors verify effective throat against blueprint specifications
- Under-calculating leads to under-sized welds that may fail
Over-calculating leads to unnecessary material and cost
Important: The ‘size’ dimension shown on the weld symbol refers to the groove depth — not the effective throat. Always apply the 5/16 × R formula when determining structural capacity unless the drawing specifies filled-flush conditions.
Single vs. Double Flare-Bevel Weld: Key Differences
Understanding the difference between single and double flare-bevel welds is essential for both reading drawings and selecting the right joint preparation.
|
Feature |
Single Flare-Bevel |
Double Flare-Bevel |
|
Joint Members |
One curved + one flat member |
Two curved members (both sides) |
|
Symbol Placement |
One symbol on reference line |
Symbols on both sides of reference line |
|
Penetration |
One-sided — weld from one direction |
Both sides — greater penetration and strength |
|
Common Use |
Pipe-to-plate, round bar-to-plate |
Tube-to-tube, structural hollow sections |
|
Weld Strength |
Good for standard loads |
Higher strength — suits heavy structural loads |
|
Fit-Up Complexity |
Simpler |
Requires precise alignment of two curved edges |
When a drawing specifies a double flare-bevel weld, both sides of the joint must be prepared and welded — and the effective throat calculation applies independently to each side. This is common in structural hollow section (HSS) fabrication in Ontario commercial and industrial builds.
Flare-Bevel Weld vs. Fillet Weld vs. V-Groove: Which to Use?
Choosing the wrong weld type is one of the most common and costly mistakes in fabrication. Here’s how the flare-bevel compares to the two weld types it’s most often confused with:
|
Feature |
Flare-Bevel |
Fillet Weld |
V-Groove |
|
Joint Geometry |
Curved edge meets flat surface |
Two flat surfaces at right angle |
Two flat surfaces, both beveled to form ‘V’ |
|
Edge Prep Required? |
No — uses natural curve |
No |
Yes — both edges must be machined |
|
Typical Members |
Round/tube to flat plate |
T-joints, lap joints |
Butt joints in structural plates |
|
Effective Throat |
5/16 × R (calculated) |
0.707 × leg size |
Full penetration if CJP |
|
Weld Symbol |
)⎺ |
Right triangle |
∧ |
|
Ontario Applications |
Pipe-plate, automotive, HSS |
Brackets, gussets, web-to-flange |
Structural beams, pressure vessels |
|
Strength Profile |
Good — geometry-dependent |
Good for shear loads |
Best for tensile/bending loads |
Rule of Thumb: Use a flare-bevel when one member is naturally curved and no edge preparation is practical. Use a fillet for right-angle joints. Use a V-groove when full or deep penetration is required in flat-to-flat butt joints.
Common Applications of Flare-Bevel Welds in Ontario
|
Application |
Description |
Ontario Context |
|
Pipe-to-Plate Joints |
Rounded pipe edge welded to flat plate surface |
Industrial and infrastructure repairs across GTA |
|
Automotive Panels |
Curved sheet metal edges welded to flat chassis components |
Automotive fabrication and repair shops |
|
Mobile Welding Repairs |
On-site welding of curved structural members to flat supports |
Construction sites, bridges, heavy equipment |
|
HVAC & Tubing |
Rounded tubes welded flush to flat panel sections |
Manufacturing plants and industrial setups |
|
HSS to Plate (Structural) |
Hollow structural sections joined to base plates |
Commercial and industrial construction in Ontario |
|
Custom Home Fabrication |
Curved architectural metalwork welded to structural plates |
Custom home builders across GTA |
5 Common Mistakes When Reading the Flare-Bevel Symbol
Mistake 1: Confusing Flare-Bevel with V-Groove
The V-groove symbol uses two straight angled lines forming a ‘V.’ The flare-bevel uses a curved arc. In low-light shop conditions or on faded blueprints, welders sometimes misread one for the other — leading to incorrect joint preparation and failed inspections.
Mistake 2: Misidentifying Arrow Side vs. Other Side
Welding on the wrong side of the joint is a serious error. Always verify whether the symbol sits below (arrow side) or above (other side) the reference line before striking an arc.
Mistake 3: Using Groove Depth Instead of Effective Throat for Calculations
The size dimension on the symbol shows groove depth — not structural throat. Always apply the 5/16 × R formula when calculating load capacity. This is one of the leading sources of nonconformities in CWB inspections.
Mistake 4: Ignoring Contour and Finish Symbols
A flat line above or below the weld symbol means the completed weld must be ground or finished flush. Skipping this step — or not noticing the symbol — results in a rejected weld and costly rework.
Mistake 5: Not Referencing the WPS
The symbol alone doesn’t tell you everything. Preheat requirements, interpass temperatures, and acceptable processes are specified in the Welding Procedure Specification (WPS). CWB-certified welders always read both the drawing and the WPS before starting.
CSA W59 vs. AWS D1.1 for Flare-Bevel Welds
Both standards govern flare-bevel weld sizing and inspection in Canada, but there are important differences every Ontario welder should know:
|
Criteria |
CSA W59 |
AWS D1.1 |
|
Jurisdiction |
Required for structural steel in Canada / Ontario |
US standard — often referenced for cross-border projects |
|
Effective Throat |
Similar formula: 5/16 × R for standard condition |
5/16 × R standard; 5/8 × R for filled-flush GMAW/FCAW |
|
Symbol Standard |
Follows ISO 2553 / CWB conventions |
AWS A2.4 symbol conventions |
|
Inspector Certification |
CWB-certified welding inspectors required |
AWS CWI certification |
|
When to Use |
All Ontario structural / commercial / industrial fabrication |
Cross-border or US client projects |
Always confirm which standard your project is specified under before beginning work. For Ontario construction, CSA W59 is the default — but some industrial or cross-border clients may specify AWS D1.1. When in doubt, ask your project engineer.
Expert Insights from Ontario Welding Professionals
“Flare-bevel welds are deceptively simple but demand careful alignment and correct fit-up. Misreading the symbol — especially confusing groove depth with effective throat — is one of the top reasons structural welds fail inspection in Ontario shops.” — John Matthews, CWB-Certified Welding Inspector, Toronto
Practical Tips from CWB-Certified Welders:
- Use proper clamping fixtures to maintain full edge contact before welding
- Pre-fit curved edges against the flat surface and check for gaps — inconsistent fit-up causes incomplete fusion
- Inspect welds against both blueprint dimensions and the applicable WPS
- On mobile welding assignments, carry portable inspection gauges for on-site throat verification
- When welding HSS (hollow structural sections), confirm whether single or double flare-bevel is specified
Need a Certified Welder in Ontario for Flare-Bevel Work?
Mobile Welding Service brings CWB-certified flare-bevel welding expertise directly to your job site — anywhere across Ontario. Their team handles:
- On-site structural repairs involving pipe-to-plate and HSS joints
- Industrial equipment welding with full WPS documentation
- Pipe and pressure system fabrication to CSA W59 standards
- Automotive and custom sheet metal projects
- Commercial and residential structural welding across the GTA
Every weld performed by Mobile Welding Service adheres to CSA W59 and CWB standards, with documentation available for inspections and project compliance. Call +1 (647) 403-9321 or schedule certified on-site welding or a free consultation.
Conclusion
Mastering the flare-bevel weld symbol is essential for any welder, fabricator, or inspector working to Canadian standards. From correctly identifying the symbol on a blueprint, to applying the 5/16 × R effective throat formula, to distinguishing single from double flare-bevel configurations — every detail matters for structural integrity, code compliance, and project efficiency.
Whether you’re studying for CWB certification, managing a fabrication shop, or working on-site across Ontario, this guide gives you the foundational knowledge to execute flare-bevel welds with confidence. For professional, CWB-certified flare-bevel welding anywhere in Ontario, contact Mobile Welding Service — fully equipped and mobile-ready for every project.
Frequently Asked Questions
What does the flare-bevel weld symbol look like?
The flare-bevel weld symbol consists of a curved arc meeting a straight horizontal line, resembling )⎺ — placed on the reference line of a welding drawing. The curved portion represents the rounded member; the flat line represents the flat plate. It is distinct from the V-groove (∧) and the J-groove (ⱼ).
What is the effective throat of a flare-bevel weld?
Per AWS D1.1 and CSA W59, the standard effective throat of a flare-bevel groove weld is 5/16 × R, where R is the radius of the curved member. When the weld is filled flush to the surface, a larger effective throat of 5/8 × R applies — provided it is verified by inspection.
What is the difference between a single and double flare-bevel weld?
A single flare-bevel weld joins one curved member to one flat surface. A double flare-bevel weld is applied to both sides of a joint — typically when both members are curved, or when greater strength and penetration are required. The symbol appears on both sides of the reference line for a double flare-bevel.
When should I use a flare-bevel weld instead of a fillet weld?
Use a flare-bevel when one member has a curved or rounded edge that naturally forms a groove against a flat surface — such as pipe-to-plate or round bar-to-plate joints. Use a fillet weld for right-angle joints between two flat surfaces. The key difference is joint geometry: flare-bevel is groove-type, fillet is corner/lap-type.
How does CSA W59 differ from AWS D1.1 for flare-bevel welds?
Both standards use a similar 5/16 × R effective throat formula for standard conditions. CSA W59 is the Canadian standard required for structural fabrication in Ontario, while AWS D1.1 is the US equivalent. Always confirm which standard your project specifies — using the wrong standard can result in failed inspections.
Can mobile welders in Ontario perform certified flare-bevel welds?
Yes. Mobile Welding Service employs CWB-certified welders fully trained to execute flare-bevel and all groove weld types on-site across Ontario. All welds comply with CSA W59, with WPS documentation available upon request.
Is a flare-bevel weld as strong as a V-groove weld?
Strength depends on the effective throat and joint conditions. A properly executed flare-bevel weld with correct effective throat provides excellent fusion and structural integrity for its application — particularly for pipe-to-plate and HSS-to-plate joints. V-grooves offer deeper penetration for flat butt joints and are preferred when maximum tensile strength is required across the full plate thickness.
