What is Bolt Clamping Force?

Bolt clamping force refers to the force that is exerted on a bolt or fastener to hold two or more objects together. This force is the compressive load on the joint members that results from the tensile force developed in a tightened bolt. In simple terms, the bolt clamp force is what holds a bolted joint together, preventing them from separating. This force is critical to the safety and stability of many structures and machines, including bridges, buildings, and vehicles.

Why is it important to measure the Bolt Clamping Force?
By measuring the clamp force one can be sure that proper preloading forces were exerted to the bolted joint so that it will be better able to support varying service loads. Inaccurate or insufficient clamping force can result in structural failures, which can lead to catastrophic consequences. For example, if a bolt in a bridge or building is not tightened sufficiently, the structure can collapse, causing severe damage and loss of life.

Measuring the clamping force of a bolt also allows for proper maintenance and repair of machines and structures. Over time, bolts can loosen or stretch, causing the clamping force to decrease. Regular measurements of the bolt clamping force can alert engineers and maintenance personnel to potential issues and help prevent failures.

How Load Cells can be used in this application?
There are various factors to consider when applying load cell sensors to measure the clamping force of a bolt. First, the load cell must be properly assembled in the fixturing elements to ensure accurate measurements. The load cell must be mounted in a way that ensures it is not subject to external forces or vibrations that could affect the bolt load measurement. This requires proper load cell geometry specification that matches the bolt and nut mechanical requirements. Additionally, the load cell must be mounted to allow easy access to the bolt or fastener being measured for future maintenance and replacement.

Second, the load cell must be properly calibrated to ensure accurate measurements. Calibration is typically done using a known weight or force, and the load cell output is adjusted to match the known value. FUTEK offers an accredited A2LA load and torque calibration lab to ensure our products are shipped with proper calibration.

Last but not least, it is important to consider the effects of thread friction and underhead friction when using load cells to measure a bolt's clamping force. These friction forces can significantly affect the accuracy of the bolt load measurement and must be properly accounted for when interpreting the load cell output.

FUTEK's Donut/Thru Hole Load Cells are major players when measuring the tightening of the load directly. Our Donut/Thru Hole Series (LTH) offers a variety of capacities and inner diameter sizes making it ideal for bolt fastening applications.

Why is it important to measure the clamping force in metal die-casting applications?

Die Casting clamping force is the force applied to a mold by the clamping unit of the die-casting machine. Using load cells to measure mold clamping forces is critical for three reasons:

• It helps ensure that the mold remains closed during the casting process, preventing any molten metal from escaping and causing safety hazards or defective parts. The clamping force also ensures that the mold halves remain aligned, preventing any warpage or distortion of the final product;
• It helps identify any issues with the mold or machine that could affect the casting process. For example, if the clamping force is not sufficient, it may indicate that the mold is worn or damaged, or that the machine needs maintenance or repair.
• Proper mold clamping force is necessary to achieve consistent casting quality and reduce scrap rates. If the force is too low, it may result in flash, where molten metal seeps out between the mold halves, or cold shuts, where the metal solidifies before filling the mold cavity completely. Both of these defects can result in scrapped parts and increased production costs.