Understanding Screw Axial Force
A screw axial force calculator estimates the clamping force created when torque turns a screw, bolt, or threaded jack. The force acts along the screw axis. It is useful for preload checks, lifting screws, fixture clamps, machine frames, and test rigs. Torque alone does not define clamp force. Diameter, pitch, thread friction, collar friction, and efficiency can change the answer greatly.
Why Friction Matters
Most tightening torque is lost to friction. Only a smaller part becomes useful axial load. A clean lubricated screw may create much higher force than a dry dirty screw at the same torque. That is why this calculator includes nut factor, thread friction, collar friction, thread angle, and efficiency methods. These options help compare practical cases instead of relying on one simple estimate.
Engineering Use
The nut factor method is fast and common for bolted joints. It uses torque, nominal diameter, and a tightening coefficient. The thread friction method is better when pitch, mean diameter, flank angle, and collar drag are known. The efficiency method is helpful for lead screws and screw jacks, where mechanical efficiency is measured or estimated.
Reading the Results
The result starts with initial axial force per screw. It then applies preload loss, screw count, and safety factor. The retained clamp force shows the useful load after relaxation, embedment, or seating loss. The stress result compares retained load with tensile stress area. Proof utilization shows how much of the selected proof load is being used.
Good Input Practice
Use consistent and realistic data. Choose torque from a calibrated wrench or design target. Use measured pitch and mean diameter when possible. Select friction from test data, coating information, or reliable tables. For safety critical assemblies, confirm preload with direct methods such as load cells, ultrasonic elongation, or validated torque angle procedures.
Limits and Assumptions
This calculator gives an engineering estimate. It does not replace joint testing, fatigue checks, bearing pressure checks, thread stripping checks, or code requirements. Real assemblies may include washers, coatings, temperature change, vibration, gasket compression, and surface settling. Use conservative factors when data is uncertain. Review outputs with an engineer before final production use. Always check material grade, engagement length, and service environment before choosing torque.