--- title: "Torque vs Preload" description: "Preload Monitoring" url: "https://strainlabs.clearagency.ai/preload-monitoring/torque-vs-preload" canonical: "https://strainlabs.clearagency.ai/preload-monitoring/torque-vs-preload" markdown_url: "https://strainlabs.clearagency.ai/preload-monitoring/torque-vs-preload.md" site: "Smart Bolts by Strainlabs" publisher: "Smart Bolts by Strainlabs" language: "en-GB" updated: "2026-11-11" breadcrumbs: - "Home: https://strainlabs.clearagency.ai/" - "Preload monitoring by Strainlabs: https://strainlabs.clearagency.ai/preload-monitoring" - "Torque vs Preload: https://strainlabs.clearagency.ai/preload-monitoring/torque-vs-preload" translations: - "sv-SE: https://strainlabs.clearagency.ai/sv/overvakning-av-forspanning/atdragningsmoment-vs-forspanning" x_default: "https://strainlabs.clearagency.ai/preload-monitoring/torque-vs-preload" --- # Torque vs Preload > Preload Monitoring _Preload Monitoring_ ## Torque vs. Preload It may seem straightforward to tighten a bolt with a certain torque and achieve a desired preload. However, there are several factors that can affect the result. What does this uncertainty mean for safety and reliability and how can one know that a bolt is tight? ![A torque wrench tightening a bolt](https://strainlabs.clearagency.ai/media/mwcnv91v-ea2jk923.webp) ### Request a demo This section is a form (“Request a demo”) that visitors fill in on the web page. It asks for: - **Name** (required): short text - **Work Email** (required): email address It is sent with the “Send” button and goes to the Smart Bolts by Strainlabs team. _Discover more:_ - Preload Monitoring ([Preload Monitoring](https://strainlabs.clearagency.ai/preload-monitoring)) - Torque vs. Preload ([Torque vs. Preload](https://strainlabs.clearagency.ai/preload-monitoring/torque-vs-preload)) - IoT & Sensor Technology ([IoT & Sensor Technology](https://strainlabs.clearagency.ai/preload-monitoring/iot-sensor-technology)) - IndTech ([IndTech](https://strainlabs.clearagency.ai/preload-monitoring/indtech)) _Definitions_ ### What is torque? - Torque definition — Torque is the length of a lever multiplied by the perpendicular force applied to it. Measuring torque is an indirect way of estimating preload. _Torque (T) = Force (F) x Length (L)_ - Torque must overcome friction — Torque is the length of a lever multiplied by the perpendicular force applied to it. Measuring torque is an indirect way of estimating preload. The majority of input torque is needed to overcome friction in the joint. _Definitions_ ### What is preload? - Preload – the axial force in the bolt — Preload is the axial force in the bolt that is introduced by tightening. A preloaded bolt creates the reactive clamping force in the joint. A bolted joint will be challenged by vibration and dynamic loads, thermal cycles and natural settlements, and relaxations in the clamped parts. Therefore, achieving and maintaining preload is critical for the bolted joints functionality. Achieving and maintaining bolt preload is critical for what external forces and environmental challenges the bolted joint can withstand. _Torque & Achieved preload_ ### The relationship between torque and achieved preload Due to the reality of the relationship between specified torque and preload outcome, it is difficult to construct a safe bolted joint from a tightening perspective. In strive of ensuring functional preload, joints are commonly over-dimensioned. - The relationship between preload and torque is linear and determined by the friction coefficient. Theoretically, a specific torque value corresponds to a specific preload value. - However, the friction coefficient is not a set value, but varies between a min and max level. Therefore, a specific torque value results in a preload value within a range. - To make matters more complicated, the tightening torque also varies due to tool inaccuracy and the operator. Thus further increasing the variation in obtained preload. _Functional Preload range_ ### What happens if the bolt preload goes below or above the functional range? - Going below minimal functional preload risks: - Lost contact (unintentional loosening) - Sliding between clamped parts - Going above maximum functional preload risks: — Yielding of bolt (i.e. overstretching), threads or the strength of the clamped surfaces _Bolt tightness_ ### How to know how tight the bolt is? Since the bolt was invented, mechanical engineers and installation teams have had to rely on torque measuring and performing impractical and manual work – without a lot of accuracy. Examples of such work include: - Measuring torque input — Measuring torque input commonly done at installation for a rough idea of preload, however, as explained above this method normally involves several unknown factors and assumptions which make it difficult to be certain that a functional preload has been achieved. - Torque check inspection — Torque check inspection is made by utilizing a calibrated torque and checking if it “clicks”. If the bolt does not move it is considered okay. The problem is though that the frictional condition could have changed significantly since tightening. - Retightening inspection — Retightening inspection is a more valid inspection compared to torque check, but it means that the tightened bolt is untightened and tightened again. Normally the force required to untighten is checked, to know that the bolt is safe. Untightening torque is often not linear to the tightening torque; however, this is a somewhat more accurate and a reliable method compared to torque check inspections. It can seem a bit ironic to have to untighten (completely loosen) a bolt to know if it is safe. So how is it possible to know if a machinery relies on the tightness of a bolt? Historically, bolt preload could only be measured under laboratory conditions. Strainlabs preload monitoring solution equips bolts with a preload-sensor that regularly reports preload levels, a solution that for many industrial applications quickly pays off compared to manual torque inspection and maintenance schedules. ### Discover the Strainlabs solution Get to know us to learn more about Internet of Bolts, Preload Monitoring and how Strainlabs System can benefit your operations. This section is a form (“Discover the Strainlabs solution”) that visitors fill in on the web page. It asks for: - **Your name** (required): short text - **Company** (optional): short text - **Phone** (optional): short text - **Work Email** (required): email address - **Message** (optional): free text It is sent with the “Send” button and goes to the Smart Bolts by Strainlabs team. ## Related pages **Part of** - [Preload monitoring by Strainlabs](https://strainlabs.clearagency.ai/preload-monitoring) ([Markdown](https://strainlabs.clearagency.ai/preload-monitoring.md)): Learn how preload monitoring helps industrial teams detect loose bolts, reduce manual inspections and prevent costly downtime. **Alongside this page** - [Business Case](https://strainlabs.clearagency.ai/preload-monitoring/business-case) ([Markdown](https://strainlabs.clearagency.ai/preload-monitoring/business-case.md)): Why loss of preload costs money and how preload monitoring will help you get the most from your assets and let your maintenance teams work smarter. - [IndTech](https://strainlabs.clearagency.ai/preload-monitoring/indtech) ([Markdown](https://strainlabs.clearagency.ai/preload-monitoring/indtech.md)): Discover how IndTech combines IT, OT, IoT sensors and data analytics to modernize industrial operations and maintenance. - [IoT & Sensor Technology](https://strainlabs.clearagency.ai/preload-monitoring/iot-sensor-technology) ([Markdown](https://strainlabs.clearagency.ai/preload-monitoring/iot-sensor-technology.md)): Learn how IoT sensor technology helps industrial teams collect data, improve safety and monitor critical bolted joints remotely. **Main pages** - [Smart Bolts with Built-in Sensors](https://strainlabs.clearagency.ai/) ([Markdown](https://strainlabs.clearagency.ai/home.md)): Strainlabs smart bolts measure preload every 10 minutes and alert you months before failure. Continuous bolt monitoring for industrial operations. - [About us](https://strainlabs.clearagency.ai/about) ([Markdown](https://strainlabs.clearagency.ai/about.md)): Strainlabs offers smart bolts with built-in sensors, paired with a system that enables real-time monitoring and alerts, to prevent unexpected production stops - [Contact](https://strainlabs.clearagency.ai/contact) ([Markdown](https://strainlabs.clearagency.ai/contact.md)): Let's talk! - [Customer cases](https://strainlabs.clearagency.ai/customer-cases) ([Markdown](https://strainlabs.clearagency.ai/customer-cases.md)): Our success stories - [Downloads](https://strainlabs.clearagency.ai/downloads) ([Markdown](https://strainlabs.clearagency.ai/downloads.md)): Learn more - [Industries](https://strainlabs.clearagency.ai/industries) ([Markdown](https://strainlabs.clearagency.ai/industries.md)): Industries - [Maintenance Glossary](https://strainlabs.clearagency.ai/maintenance-glossary) ([Markdown](https://strainlabs.clearagency.ai/maintenance-glossary.md)): All Key Terms in Maintenance & Reliability Explained - [Our Solution](https://strainlabs.clearagency.ai/our-solution) ([Markdown](https://strainlabs.clearagency.ai/our-solution.md)): Our Solution - [Part of Service Offering](https://strainlabs.clearagency.ai/part-of-service-offering) ([Markdown](https://strainlabs.clearagency.ai/part-of-service-offering.md)): Application and industries - [Partners](https://strainlabs.clearagency.ai/partners) ([Markdown](https://strainlabs.clearagency.ai/partners.md)): Local expertise. Global reach. - [Privacy policy](https://strainlabs.clearagency.ai/privacy-policy) ([Markdown](https://strainlabs.clearagency.ai/privacy-policy.md)): Last updated: 2021-08-25 - [Request a demo](https://strainlabs.clearagency.ai/request-a-demo) ([Markdown](https://strainlabs.clearagency.ai/request-a-demo.md)): Want to know more? Request a demo - [Sustainability](https://strainlabs.clearagency.ai/sustainability) ([Markdown](https://strainlabs.clearagency.ai/sustainability.md)): Preload monitoring ## How to cite Smart Bolts by Strainlabs. “Torque vs Preload”. Smart Bolts by Strainlabs, 2026-11-11. https://strainlabs.clearagency.ai/preload-monitoring/torque-vs-preload (accessed ). ## Company & contact - **Company:** Smart Bolts by Strainlabs - **Address:** Strainlabs head office, Stockholm: | Kungsgatan 64, 111 22 Stockholm - **General enquiries:** [contact@strainlabs.com](mailto:contact@strainlabs.com) - **Phone:** +46 (0) 46 286 4000 - **About:** Get to know us to learn more about Internet of Bolts, Preload Monitoring and how Strainlabs System can benefit your operations. **Other languages:** [Svenska](https://strainlabs.clearagency.ai/sv/overvakning-av-forspanning/atdragningsmoment-vs-forspanning.md) --- [View on site](https://strainlabs.clearagency.ai/preload-monitoring/torque-vs-preload) · [Site index for agents (llms.txt)](https://strainlabs.clearagency.ai/llms.txt)