Your tool supplier offers "calibration included". That sounds convenient - but what exactly are you getting? Is it a DAkkS-certified calibration with assured traceability? Or a factory calibration that comes with a certificate, but no accreditation mark? In day-to-day operations this may seem like a minor distinction. In an audit or in the event of damage, it can be critical.
This article explains, in a neutral and factual way, how the two methods differ - and when you actually need which type of calibration. As the second part of our practical campaign "Calibration & Service", this article builds directly on the fundamentals we covered in our guide on calibrating torque wrenches.
What Is a Factory Calibration?
Factory calibration - often referred to as ISO calibration - is performed by the manufacturer or by a non-accredited laboratory. Calibrations carried out outside an accreditation framework are always based on the voluntary self-commitment of the respective lab and are not monitored by DAkkS.
The result is a factory calibration certificate documenting measurement values and deviations - but without the DAkkS accreditation mark. Accredited calibration certificates must display the DAkkS logo together with an individual accreditation number. Factory certificates do not carry this symbol and are therefore not covered by the EA-MLA.
What a factory calibration delivers:
- Documents the measurement deviation of the tool against a reference standard
- Creates a traceable test record for basic audit documentation
- Is usually more cost-effective and faster to obtain
- Is sufficient for ISO 9001-compliant processes in many cases
What it does not deliver:
- No external monitoring of the calibration laboratory by an independent authority
- No guaranteed, fully documented calibration traceability to national standards
- The test certificates do not have worldwide validity - many auditors also reject them at national level, which is permissible within the scope of audits
Factory calibration can be an efficient calibration service for simple applications, but it is not a regulated calibration in the strict sense.
What Is a DAkkS Calibration?
DAkkS is the national accreditation body of the Federal Republic of Germany and is authorized to issue conformity certificates for calibration laboratories. A DAkkS calibration means that the instrument has been calibrated in a DAkkS-accredited lab in line with internationally recognized standards.
Accredited calibrations are regularly audited and monitored by the Deutsche Akkreditierungsstelle in terms of form, structure, and content. DAkkS ensures that the laboratory has the necessary technical competence, equipment, and an appropriate management system.
The result is a DAkkS calibration certificate with the accreditation mark - a globally recognized proof that the measurement is traceable and that the procedure is externally supervised, from the reference standards through to the final calibration certificate.
What a DAkkS calibration guarantees:
- Calibration in accordance with DIN EN ISO/IEC 17025 by an accredited laboratory
- Complete, externally monitored calibration traceability to national standards (PTB)
- Full specification of measurement uncertainty according to GUM
- International recognition of the calibration certificate in all countries whose accredited institutions have signed the multilateral agreements (MLA): EA, IAF, and ILAC
- Unrestricted acceptance for IATF 16949, EN 9100, and customer audits
In other words: DAkkS calibration is the benchmark for safety-critical connections and for all applications where production traceability and audit documentation must be watertight.
The Critical Difference: Traceability
The core difference between the two methods is not the measurement result itself - it is the proven quality of this result.
Only calibration in accordance with ISO 17025 guarantees traceability to the national standard.
What traceability means in practice: A continuous chain of comparison measurements that can be traced back to the Physikalisch-Technische Bundesanstalt (PTB). DAkkS calibrations are carried out with reference standards that are regularly recalibrated by PTB or a DAkkS-accredited lab. These calibrations can only be issued by a DAkkS-accredited calibration laboratory and only in line with binding standards and guidelines. This is the essence of regulated calibration.
In the case of factory calibration, by contrast, responsibility for ensuring traceability lies solely with the laboratory's own self-commitment - there is no external control. Factory calibrations rely on the lab's internal promise of correct indication of measurement uncertainty, traceability, and careful lab practice.
Why This Matters in the Event of Damage
In the context of product liability, acceptance testing, or expert assessments, DAkkS calibration is the standard. Courts and insurers accept DAkkS calibration certificates as proof that the measuring equipment has been properly verified. A factory certificate without an accreditation mark represents an increased risk in such situations - because you must then prove that the issuing lab is trustworthy and competent.
For more on this, see our article on liability risks in bolted joint assembly.
Direct Comparison: Factory Calibration vs. DAkkS Calibration
| Characteristic | Factory calibration | DAkkS calibration |
|---|---|---|
| Performing laboratory | Manufacturer or non-accredited laboratory | DAkkS-accredited laboratory (DIN EN ISO/IEC 17025) |
| Traceability to national standards | Laboratory self-declaration - no external verification | Assured and regularly monitored by DAkkS |
| Calibration certificate | Factory calibration certificate - without DAkkS accreditation mark | DAkkS calibration certificate with accreditation mark |
| International recognition | Restricted - sometimes rejected by auditors | Worldwide recognized (EA-MLA, ILAC, IAF) |
| External monitoring of the laboratory | None | Regular appraisal by DAkkS |
| Measurement uncertainty specification | Fundamental - not always complete | Fully in accordance with GUM, transparently documented |
| Acceptance in IATF 16949 / EN 9100 audits | Restricted - risk of non-recognition | Fully recognized |
| Suitability for Category-A fastenings (VDI/VDE 2862) | Not sufficient | Yes - mandatory |
| Costs | Cheaper | Higher, but legally compliant |
| Typical use | C-fastenings, internal test equipment without audit relevance | A- and B-fastenings, all audited processes |
When Is Factory Calibration Sufficient?
Factory calibration is not inherently inferior - for certain applications it is the right and most economical choice of calibration service:
- Category C bolted joints according to VDI/VDE 2862, where there is no safety or functional risk
- Internal measuring equipment without audit relevance, which is used exclusively within your own organization
- Interim checks between regular calibration intervals to detect deviations at an early stage - as a complement to DAkkS calibration
- Processes that are certified only under ISO 9001 and do not have to comply with sector-specific standards such as IATF 16949
In these scenarios, a factory calibration can provide sufficient audit documentation while keeping costs and turnaround times low.
When Is DAkkS Calibration Mandatory?
There are three typical situations where you unequivocally need DAkkS-accredited calibration:
1. Category A and B bolted joints according to VDI/VDE 2862
Bolted joints in Category A according to VDI/VDE 2862 pose a risk to life, limb, and the environment in the event of failure. Category A bolted joints pose a risk to life, limb, and the environment if they fail. Category B bolted joints pose a risk of functional failure. Category C bolted joints do not pose a safety or functional risk.
According to guideline VDI/VDE 2862 Sheet 2, tools used in production for these categories must be tested by an accredited testing laboratory - in practice, that means a DAkkS accredited lab with DAkkS certified procedures for torque and angle.
2. Audit-relevant processes under IATF 16949 and EN 9100
IATF 16949 section 7.1.5.3.2 stipulates that calibration certificates must bear an accreditation mark from the national accreditation body.
IATF 16949, Section 7.1.5.3.2: Calibration certificates must bear an accreditation mark of the national accreditation body. A pure in-house calibration without a DAkkS mark does not fulfill this requirement in IATF-16949-audited processes not - and may be recorded as a finding in the audit.
The trigger for the stricter requirements was the IATF 16949 standard with its extended demands on "monitoring and measuring resources". It states that "the relevant calibration service shall be included in the scope of the accreditation. Calibration certificates shall bear the accreditation symbol of a national accreditation body."
In the automotive industry, accredited calibration is therefore a mandatory requirement under IATF 16949 for external labs. In aerospace, EN 9100 defines the highest safety level and likewise expects accredited calibration and full calibration traceability.
3. Wherever traceability must be proven without gaps
Whenever customers, authorities, or courts require proof that your measurements are traceable to international standards, a DAkkS calibration certificate is the only document that fully and externally confirms this requirement.
You will find a concise overview of all 10 aspects that auditors check in bolting processes - including calibration traceability and audit documentation - in our audit checklist for bolted joint processes.
Your Quick Check: DAkkS or Factory Calibration?
Unsure which method your application requires? Answer four short questions and receive an immediate, clear assessment:
Cost Comparison: What You Are Really Paying For
At first glance, factory calibration is cheaper - and that is true. A test in accordance with DIN ISO 9001 involves lower direct costs than a DAkkS calibration.
However, this cost advantage can quickly reverse once you consider the follow-up costs:
| Cost factor | Factory calibration | DAkkS calibration |
|---|---|---|
| Direct calibration costs | Lower | Higher |
| Recalibration due to audit findings | Yes - double effort | Not required |
| Risk in safety-relevant damage cases | Increased (missing traceability) | Minimized |
| International validity | Limited | Full |
| Regular external lab surveillance | None | Included (by DAkkS) |
| Audit security for IATF 16949 / EN 9100 | Not ensured | Fully ensured |
The key question: What is the risk if your calibration certificate is not accepted in an audit - and all affected tools have to be recalibrated? Your decision between DAkkS calibration and factory calibration directly influences market access, product liability, and your quality reputation.
Factory calibration offers short-term cost benefits, but DAkkS calibration ensures long-term competitiveness - especially in regulated markets with zero-defect tolerance and strict calibration traceability requirements.
The GWK DAkkS Calibration Laboratory: Precision at Class 0.2
GWK operates its own DAkkS calibration laboratory - with the fully automated DWPM-1000c test machine at its heart. This calibration bench in accuracy class 0.2 covers a measuring range from 2-1000 Nm and enables standard-compliant test routines according to DIN EN ISO 6789 and VDI/VDE 2648 - fully automated, documented, and traceable.
This DAkkS accredited lab is designed specifically for highly precise torque and angle tools in safety-critical connections and demanding production environments.
What the GWK lab offers:
- Stationary calibration in our lab in Schauren - with full DAkkS documentation and a DAkkS calibration certificate for your audit documentation
- Mobile calibration on site - GWK performs on-site calibration directly in your production to minimize downtime, combining maximum availability with complete calibration traceability
- Third-party tools - you can also submit torque and angle torque wrenches from other manufacturers for DAkkS calibration
- Calibrated upon delivery - all GWK tools leave our factory with a valid DAkkS calibration certificate
For you, this means: Whether you receive a QUANTEC MCS® analysis tool for your development department or an OPERATOR® production tool for the assembly line, the calibration certificate is already included - audit-ready, without additional effort.
Our Q-CHECK® quality assurance tool for residual torque measurements and process capability studies (PFU) according to VDI/VDE 2645-3 is likewise delivered calibrated. Important: Q-CHECK® is a QA and audit tool - not a calibration device. The actual regulated calibration is carried out by the DWPM-1000c in the DAkkS calibration laboratory.
And If You Do Not Want to Buy Your Own Tool?
With the GWK ToolRent® rental system, you get calibrated measuring devices on demand - with no capital investment and no own calibration effort. Whether weekly, monthly, or annual rental: the devices are supplied with a valid DAkkS calibration certificate and are ready for immediate use.
This is particularly attractive for:
- Project-based measurement tasks without long-term demand
- Bridging solutions during maintenance or calibration intervals
- Pilot lines, ramp-ups, and prototype builds
- Companies that want to minimize capital costs while still ensuring audit-safe documentation and full calibration traceability
ToolRent combines the advantages of DAkkS certified equipment with the flexibility of mobile calibration and on-site calibration logistics.
Conclusion: Decide Correctly Once - No More Audit Surprises
Factory calibration is not a bad method - for many applications it is the economically sensible choice. However, as soon as standards such as IATF 16949 or EN 9100 apply, Category A or B bolted joints according to VDI/VDE 2862 are involved, or traceability has to be demonstrated without any gaps, there is no way around DAkkS calibration in a DAkkS accredited lab.
The good news: You do not have to make this decision alone. With its DAkkS calibration laboratory, mobile calibration and on-site calibration service, and the flexible ToolRent® rental system, GWK provides a partner who supports you from the very first calibration certificate all the way through to passing the most demanding audits. Accuracy by GWK.
Frequently Asked Questions: DAkkS vs. Factory Calibration
Is a factory calibration basically worthless?
No. Factory calibration is absolutely sufficient for many applications — especially for Category-C fastenings and internal testing equipment without audit relevance. However, it is subject to the laboratory's own commitment and is not externally monitored by the DAkkS. Where traceability must be proven without gaps, it is not sufficient.
Must my calibration certificate bear the DAkkS logo?
Yes. For processes audited to IATF-16949 and EN-9100, as well as Category-A and B fastenings according to VDI/VDE 2862, yes. IATF 16949 (Chapter 7.1.5.3.2) explicitly requires calibration certificates to carry an accreditation mark. A factory calibration certificate without this symbol is not a fully valid proof in the audit.
What does 'traceability' mean concretely?
Traceability describes an unbroken chain of comparison measurements that can be traced back to a national or international primary standard — in Germany the Physikalisch-Technische Bundesanstalt (PTB). Only a DAkkS-accredited laboratory can demonstrate this chain in a binding and externally verifiable manner.
Can GWK calibrate tools from other manufacturers as well?
Yes. The DAkkS-accredited calibration laboratory at GWK calibrates not only its own tools but also third-party tools in the 2-1000 Nm measurement range. The calibration is performed fully automatically with the DWPM-1000c (accuracy class 0,2), either stationary or mobile on-site.
What happens if my expired certificate is detected during the audit?
An expired calibration certificate is one of the most common audit findings. In the best case, it leads to a deviation with a deadline for rectification. In the worst case—especially for safety-critical A-class fastenings—production stoppage, recall of already manufactured parts, or liability issues under the Product Liability Act (ProdHaftG) may occur.
How often does a torque wrench need calibration?
According to DIN EN ISO 6789: recalibration at the latest after 12 months or 5.000 uses—whichever occurs first. After a drop, overload or repair, immediate recalibration is required, regardless of the interval.
