API FAQ ARCHIVE

En Iso 13920-bf

Title: Understanding EN ISO 13920-BF: General Tolerances for Welded Constructions and Position Tolerances for Plates

Introduction: The European Standard EN ISO 13920 provides general tolerances for welded constructions and position tolerances for plates. The standard is essential for ensuring the quality and accuracy of welded products, which are widely used in various industries, including construction, manufacturing, and engineering. In this blog post, we will focus on the key aspects of EN ISO 13920-BF, a specific part of the standard.

What is EN ISO 13920-BF?

EN ISO 13920-BF specifies general tolerances for welded constructions and position tolerances for plates. The standard applies to welded constructions made from steel, aluminum, and other metals. The tolerances specified in EN ISO 13920-BF are essential for ensuring that welded products meet the required quality and accuracy standards.

Key Aspects of EN ISO 13920-BF:

Importance of EN ISO 13920-BF:

EN ISO 13920-BF is crucial for ensuring the quality and accuracy of welded products. The standard helps to:

Industries Affected by EN ISO 13920-BF:

EN ISO 13920-BF applies to various industries, including:

Conclusion: EN ISO 13920-BF is an essential standard for ensuring the quality and accuracy of welded constructions and position tolerances for plates. The standard provides general tolerances and position tolerances that help to promote interchangeability, reduce errors, and improve quality. By understanding and applying EN ISO 13920-BF, industries can ensure that their welded products meet the required quality and accuracy standards.

Recommendations:

The designation EN ISO 13920-BF a specific set of general tolerances for welded constructions, combining two different accuracy classes defined in the for linear/angular dimensions and for form and position Breakdwon of "BF" When this standard is cited on a drawing (e.g., ISO 13920-BF ), it indicates the following requirements: B (Linear/Angular Dimensions):

This is the "Medium" (mean) tolerance class for lengths and angles. F (Shape and Position):

This class governs tolerances for straightness, flatness, and parallelism. Key Tolerance Categories ISO 13920 standard

replaces individual tolerance callouts on drawings with general workshop-based standards. CertBetter Tolerance Classes Available Class in "BF" Description Linear & Angular A, B, C, D Medium Accuracy

: Standard workshop accuracy for most general steel constructions. Shape & Position E, F, G, H Medium Form Tolerance

: Defines limits for straightness and flatness based on the largest dimension of the part. Application Rules ISO 13920 An Explained Guide to Welding General Tolerances

EN ISO 13920-BF is a specific technical designation used in engineering drawings to define general tolerances for welded constructions. It combines two distinct precision levels from the ISO 13920 standard to ensure that welded parts fit together correctly without needing individual, complex dimensioning for every single weld. Breaking Down the Code: "BF"

The suffix BF tells the manufacturer exactly which tolerance "bracket" to use for different types of measurements:

B (Linear & Angular Dimensions): This represents the "Medium" or "Mean" tolerance class. It is the most commonly used class in general engineering and steel construction. It provides a balance between functional accuracy and cost-effective fabrication. en iso 13920-bf

F (Shape & Position): This refers to the tolerance for straightness, flatness, and parallelism. While linear dimensions use letters A through D, shape and position tolerances use E through H. Class F is the second-most precise level in this category (often considered "Medium" for shape). Why Use EN ISO 13920-BF?

Using this standard shorthand simplifies communication between designers and fabrication shops. Instead of calculating individual limits for every length and angle, a single note—EN ISO 13920-BF—applies a pre-defined set of rules based on the size of the component.

Neutral Benchmarking: It acts as a universal language for international contracts, ensuring a manufacturer in Europe and a client in the Middle East have the same expectations for accuracy.

Cost Efficiency: Specifying "Class B" avoids the high costs associated with the ultra-precise "Class A," while preventing the safety or assembly risks of the looser "Class C".

Broad Application: This standard is widely used in machine construction, steel structures, rail vehicles, and shipbuilding. Tolerance Tables Overview

The actual permissible deviation (in millimeters or degrees) depends on the nominal size of the part. For example, a 1,000 mm beam in Class B will have a specific allowed variation, whereas a 10,000 mm beam will have a larger allowable margin. Type of Measurement Class for "BF" Key Focus Areas Linear Dimensions B (Medium) Length, width, and height of parts. Angular Dimensions B (Medium) Deviations in angles and slopes. Shape & Position F (Medium) Straightness, flatness, and parallelism. Testing and Verification

Compliance with EN ISO 13920-BF is verified using standard workshop tools such as steel straightedges, tape measures, and vernier callipers. It is important to note that this standard covers dimensional accuracy, not weld quality (like cracks or porosity), which is instead governed by ISO 5817. IS0 13920 - iTeh Standards

EN ISO 13920-BF is a combined tolerance designation used in the fabrication of welded structures to specify acceptable deviations in dimensions and shape without detailing every single measurement on a technical drawing. Standard Breakdown EN ISO 13920

: The international standard for "General tolerances for welded constructions". : Refers to the tolerance class for linear and angular dimensions

(lengths and angles). Class B is generally considered "medium" or standard workshop accuracy. : Refers to the tolerance class for shape and position

(straightness, flatness, and parallelism). Class F is often used for structural assemblies where moderate precision is required. Summary of Tolerances

The exact deviation allowed depends on the nominal size of the component. Larger components are permitted greater absolute deviations than smaller ones. Linear Dimensions (Class B)

Class B specifies the following typical tolerances based on the length ( ) of the part: plus or minus 1.0 plus or minus 1.0 plus or minus 3.0 plus or minus 6.0 (Tolerances continue to scale for larger structures) Shape and Position (Class F)

Class F governs how much a part can warp or sit out of alignment (straightness, flatness, and parallelism): : Max deviation of : Max deviation of : Max deviation of Why This is Used Using a general tolerance like EN ISO 13920-BF

simplifies technical drawings by removing the need for hundreds of individual plus or minus

callouts. It ensures that different fabrication shops produce parts to a consistent quality level, reducing the risk of components not fitting together during final assembly. comparison table

of the different tolerance classes (A, B, C, and D) to see which fits your project best? EN ISO 13920

EN ISO 13920-BF is a specific tolerance designation for welded constructions that combines two different accuracy levels for dimensions and geometry .

B (Medium): This refers to the tolerance class for linear and angular dimensions (length, width, height, and angles) . It is based on "customary workshop accuracy" and is the most common class used in general engineering . Title: Understanding EN ISO 13920-BF: General Tolerances for

F (Medium): This refers to the tolerance class for shape and position (straightness, flatness, and parallelism) . Key Features of ISO 13920 ISO 13920 An Explained Guide to Welding General Tolerances

The designation EN ISO 13920-BF refers to a specific combination of tolerance classes for welded constructions. It is a standard shorthand used in engineering drawings to define acceptable variations in dimensions without needing to label every single part. Breaking Down "BF"

The code is split into two distinct parts that cover different geometric features: B (Linear and Angular Dimensions):

This is the tolerance class for lengths (like the distance between two plates) and angles. Class

is considered "medium" or customary workshop accuracy for welded parts. F (Shape and Position): This refers specifically to straightness, flatness, and parallelism

defines how much a welded beam can bow or a plate can warp during the welding process. American National Standards Institute - ANSI Key Features of the Standard

ISO 13920:2023 - Welding Tolerances for Dimensions and Positions

EN ISO 13920-BF is a specific technical standard for general tolerances in welded constructions, the best way to make it "interesting" is to highlight how it prevents costly manufacturing headaches. Here are two options depending on your platform: Option 1: The "Problem-Solver" (Best for LinkedIn)

Headline: Why your welds are great, but your assembly still doesn't fit.

Ever finished a perfect weld only to find the final structure is a few millimeters off? That’s where EN ISO 13920 Specifically, class

is the "sweet spot" for many industrial steel constructions: covers linear and angular dimensions (Fine/Medium balance). handles straightness, flatness, and parallelism. Using a standardized tolerance like Clear Communication:

Your fabricators know exactly how much "wiggle room" they have without constant back-and-forth. Cost Control:

You aren't paying for "precision machining" tolerances on a heavy structural frame where they aren't needed. Interchangeability:

Parts made in different shops actually fit together on-site.

Stop guessing and start specifying. Are you using BF for your general steelwork, or do you prefer a tighter tolerance?

#Welding #Engineering #Manufacturing #ISO13920 #SteelConstruction #QualityControl

Option 2: The "Technical Deep Dive" (Best for a Blog or Newsletter)

Decoding the Blueprint: What does "EN ISO 13920-BF" actually mean? If you see ISO 13920-BF

in a title block, the designer is giving the workshop a roadmap for accuracy. Here is the breakdown: The Scope: Linear dimensions (e

This standard applies to welded structures (not machined parts). It accounts for the heat distortion and shrinkage inherent in welding. The "B" (Length/Angles):

This is the tolerance class for linear dimensions. For a length of 2 meters, a "B" rating allows for roughly of deviation. The "F" (Form):

This covers the "straightness" of the beam or the "flatness" of a plate. It ensures that while the part might be the right length, it isn't "banana-shaped" or twisted.

If your assembly requires high-precision robotic integration later, BF might be too loose. But for 90% of general structural steel, it’s the gold standard for balancing cost and quality.

In the world of metal fabrication, EN ISO 13920-BF isn't just a string of characters—it's the set of rules that keeps heavy structures from being "crooked." If you're building something like a heavy-duty roll trailer desorber unit , this standard is your blueprint for precision. The Story of the "Perfectly Imperfect" Weld

Imagine a team of engineers designing a massive steel frame. They know that when you apply intense heat to metal during welding, it expands, contracts, and twists. Without a shared "tolerance" agreement, the person welding the frame might think a 5mm warp is fine, while the person installing the machinery on top thinks it's a disaster. This is where EN ISO 13920 steps in. It provides a common language for general tolerances for welded constructions Breaking Down the "BF" The suffix

is the specific "handshake" between the designer and the workshop: B (Linear/Angular Dimensions):

This is the "Medium" tolerance class. It’s like saying, "We need this to be accurate, but we aren't building a watch." It allows for small variations in length and angles that are typical for professional workshop accuracy. F (Shape and Position):

This refers to how straight or flat the structure is. Class "F" is a common standard for general engineering, ensuring the final piece isn't so distorted that it won't fit into its designated space. Why it Matters By specifying EN ISO 13920-BF on a drawing, a company like NOVATECH ApS

ensures that their 13-ton trailers are built to a consistent quality. It prevents expensive "re-work" and ensures that if a part is made in one factory, it will perfectly match a part made in another. exact measurement tables for the "B" and "F" classes to use on a technical drawing?

This review is designed for engineering, quality assurance, and drafting departments to determine if this standard is suitable for a given project.

Example: Linear Dimensions (Class B)

If you have a welded beam with a nominal length of 1000 mm:

5. Practical Application Example

Scenario: Fabricate a welded steel frame, 2000 mm long, with a backing run on the main butt joint.

Correct specification:

If someone wrote "EN ISO 13920-BF" on a drawing:
You would ask for clarification. Likely they want:

4. How to Specify Correctly

What the "BF" preparation means:

What is EN ISO 13920?

Before diving into the "BF" subclass, it is essential to understand the parent standard.

EN ISO 13920 (full title: Welding — General tolerances for welded constructions — Linear and angular dimensions — Shape and position) is the European adoption of the international ISO standard. It serves as a universal reference for permissible deviations in welded assemblies.

Unlike machining tolerances (which are very tight), welding tolerances account for the inherent variability of heat-based joining processes. The standard provides five distinct tolerance classes: A (fine), B (medium), C (coarse), D (very coarse), and E (extremely coarse). These classes allow designers to specify how much deviation is acceptable based on the function of the part.

Common confusion:

Thus, "EN ISO 13920-BF" is not a valid tolerance class – it likely means:
Use ISO 13920 (unspecified class, usually Class D or E) + BF weld prep (ISO 9692-1).

API FAQ Privacy Terms Contact
System Status: Stable

By using PasteCode you agree to our cookies policy to enhance your experience

Site design by Brill Vast Almanac. All rights reserved. © 2026