When you look at a Kuna Torque & Tool calibration certificate, you'll see "ASME B107.300" referenced as the methodology standard. This article explains what that means, why it matters, and why it's the appropriate standard for torque wrench calibration in the US.
What ASME Is
The American Society of Mechanical Engineers is one of the oldest and most respected professional engineering organizations in the world. Founded in 1880, ASME develops consensus-based standards used across virtually every field of mechanical engineering — pressure vessels, elevators, pipelines, and yes, hand tools including torque instruments.
ASME standards are developed by technical committees made up of engineers, manufacturers, regulators, and users. They go through rigorous review, public comment, and revision cycles. When ASME says a test method is the standard, it's because hundreds of people with relevant expertise agreed it was — not because one lab or manufacturer decided so.
What B107.300 Actually Requires
For calibration purposes, the key requirements are:
- Test points — calibration must be performed at 20%, 60%, and 100% of the wrench's rated capacity. Testing only at the middle of the range doesn't meet the standard.
- Accuracy tolerances — click and dial type wrenches must be within ±4% of indicated value at each test point. Electronic types must be within ±2%.
- Number of readings — the standard specifies minimum readings per test point to establish a valid result, not just a single pass.
- Reference standard requirements — the equipment used to calibrate must itself be calibrated and traceable to a national standard.
- Direction of testing — clockwise testing is required for all wrenches; counter-clockwise testing is required for reversible types.
Why test at 20%, 60%, and 100%? A wrench that's accurate at its rated capacity may be significantly off at lower settings — and most real-world torque applications don't happen at the wrench's maximum. Testing across the range gives a complete picture of actual accuracy.
Why This Standard and Not Another?
Other standards exist — ISO, military specifications, OEM requirements. For general commercial and industrial use in the United States, ASME B107.300 is the appropriate choice for several reasons:
- It's the US consensus standard — widely recognized by manufacturers, OEMs, quality systems, and auditors
- It's designed for the tool type — unlike general measurement standards applied to torque tools, B107.300 was written specifically for torque instruments
- It's what most quality programs reference — ISO 9001 quality systems, OEM service requirements, and fleet maintenance programs typically accept or require ASME B107.300 calibration documentation
- It provides clear pass/fail criteria — the tolerance requirements are explicit and verifiable, which makes the certificate meaningful
Standards vs Accreditation
It's important to distinguish between following a standard and being accredited. ASME B107.300 is a methodology standard — it defines how to perform the calibration. Accreditation (like ISO 17025) is a third-party verification that a laboratory has a quality management system in place.
For torque wrench calibration in most shop and fleet environments, following ASME B107.300 with NIST-traceable reference standards produces results that are technically equivalent to accredited lab results. The standard is the same. The traceability is the same. What differs is the overhead — and who pays for it.
The standard is the substance. A certificate that references ASME B107.300 and NIST-traceable standards tells you exactly how the calibration was performed and what it was measured against. That's the information that matters for most applications.
What "NIST Traceable" Means in This Context
ASME B107.300 requires that calibration be performed using reference standards with known, documented accuracy traceable back to national measurement standards. In the US, that means NIST — the National Institute of Standards and Technology, which maintains the national measurement reference standards.
Kuna Torque & Tool achieves traceability by sending our reference standards to a NIST-traceable calibration laboratory for regular calibration. Those lab certificates document the chain: our standards → traceable lab → NIST. When we calibrate your wrenches against our standards, that traceability chain extends to your certificate.
This is the same traceability model used by the vast majority of calibration services — including many accredited laboratories. The difference is in documentation overhead, not technical substance.
Questions About Our Methodology?
We're happy to discuss our calibration process, traceability documentation, or whether our service meets your specific quality requirements.
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