Measuring Clamp Load in a Bolted Joint

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A clamp load, also referred to as a preload, is the force that holds a joint together. In a bolted joint, the compression occurs on the surface of impact between two parts of the joint, creating a clamping force. When used in bolted joints, this creates tension that keeps the bolt together and makes it stronger and more reliable. If the clamp load of a bolted joint is too high, it could lead to wear and tear on the threads. If it is too low, the bolt may loosen.

Methods of Measuring and Estimating Clamp Load

There are various methods to measure or estimate clamp load in bolted joints. Each method has its own pros and cons but may be more useful in certain situations than others.

The Force Torque Method

One of the most common forms of determining preload in a bolted joint is using a specially designed force-torque sensor. By attaching the sensor to a torque wrench, you can measure the amount of needed force to loosen or tighten the bolt, resulting in a reading of clamp load values.

The Proof Load Method

Proof load shows an estimation of the elastic range of the bolt and can help prevent deformation. This method is conducted by measuring the amount of force that can be applied to a bolt before it deforms by using a load cell sensor to measure the torque and load relationship.

The Turn-of-Bolt Method

Possibly the simplest and most economical way to get a clamp load estimate, it involves marking both sides of the bolted joint with a permanent marker or paint and applying torque until the position has changed by 90 degrees. The clamp load is determined by the amount of torque it took to achieve this rotation, and this torque could be measured with a torque wrench. This is also known as the torsional angle.

Measuring and estimating clamp load in bolted joints is essential for engineers. With the range of methods available, it’s important to understand how they can be used depending on the specific application. By taking the necessary measurements, you’ll be able to create better designs with a more reliable clamp load that will last for years to come. At Electronic Fasteners, we understand the importance of measuring and estimating clamp load in bolted joints and have a variety of products suitable for every application. If you have any questions about how to get the perfect clamp load for your bolted joints, contact us today to get started.