There are a lot of technical terms we throw around when it comes to the quality of screws and making sure they hold up. We have defined a few below so you know what factors to look for when fastening together your next project.
This is how much axial load a screw can withstand without breaking.
Yield strength is the amount of resistance of a material to plastic deformation, so it determines how much stress a screw must withstand with the bolt being permanently elongated.
Proof Load is the amount of resistance of a material to plastic deformation, so it determines how much stress a screw must withstand without being permanently elongated.
Tensile Strength under Wedge Loading
Bolts and screws are subject to the wedge test to measure ductility and head integrity. The test is performed by placing a wedge below the screw head and the screw must break in the thread or in the shank.
The screw head must not have signs of cracking after being formed being cold formed.
There are different tests for hardness like Vickers hardness, Brinell hardness or Rockwell hardness, but they all measure the resistance of the material to penetration by a test body.
Notch Impact Strength
This is the impact energy consumed during notch impact testing. Testing gives information on micro-structure, steel making process, inclusion content and more.
Surface defects can be multiple things. They can arise in the semi-finished product and those would be called slag inclusions, material folds and die marks. Also there could be cracks or crystalline breaks without inclusion of foreign materials.
This is the loss of carbon at the surface of ferrous materials.
We hope these definitions helped you learn a little bit more about the technical terms that can be thrown around in different projects. If you have any questions, contact us at ProvenProductivity@bossard.com.
Mechanical Properties for Screws by Bossard