NK Series Screw Torsional Strength Testing Machine

Overview

The NK Series Screw Torsional Strength Testing Machine is designed to evaluate the torsional performance of screws. The screw is clamped into a split chuck featuring an internal thread, and torque is manually applied using a torque wrench until the screw fails by torsional fracture.

1. Torsional Failure Test

If the applied torque does not meet the specified minimum requirement, the product is deemed non-compliant. Non-compliance may indicate that the screw material is too soft or that the root diameter is insufficient.

2. Driving Test

In addition to torsion testing, a driving test can be conducted by screwing the test specimen into a specially prepared test plate with specified hardness, thickness, and hole diameter. If the screw drives through the plate but becomes deformed, the product is also deemed non-compliant. This may indicate inadequate or shallow surface hardening of the screw.

3. Driving Torque Test

This test is required for thread-rolled screws only. The test involves driving the screw into the test plate while measuring the peak driving torque. If the torque exceeds the standard specified value (which varies depending on the screw’s size and surface treatment), the product is considered non-compliant. Such non-compliance may be caused by insufficient surface lubrication or improper thread formation requiring excessive torque.

4. Torsional Resistance

A screw’s torsional resistance indicates its ability to withstand being twisted until failure. Most screw standards define minimum torsional strength requirements for self-tapping screws.