Illustrative image: testing tasks for metallic fasteners.
Materials testing · Fasteners
Fastener testing: which test suits your component?
Bolts, screws, nuts and studs serve different purposes. Fastener testing therefore starts with what you need to know: how hard is the component, and how has heat treatment affected it? How much load can it carry? Or how does the assembled joint behave? This page helps you choose the right starting point for your testing enquiry.
Testawell offers Vickers, Rockwell and Brinell hardness testing. We measure hardness in the core and at the surface, and hardness profiles across ground and polished sections. Testawell is currently not accredited to DIN EN ISO/IEC 17025. If you need an accredited test report, arrange the testing in advance with a laboratory accredited for the required method.
What do you need to know about your fastener?
Incoming inspection often asks: does the delivered batch meet the purchase order and drawing requirements? After heat treatment, the hardness of the core and the condition near the surface matter. For a broken part, the fracture surface, previous loads and material condition are also examined. A single measured value cannot answer all these questions.
Start by describing why testing is needed and which decision you want to make using the result. We can help especially with hardness testing of bolts and screws and choosing suitable measurement locations. Whether and how other types of testing are possible must be agreed separately.
Choosing the right requirements for bolts, screws, nuts and studs
The requirements depend on material, design and loading. A metric steel bolt, a nut and a stainless steel screw may therefore need different tests. The table gives an initial guide. Before testing, check whether the standard applies to your component. [1][2][3]
Component
Standard to check
What matters
Bolts, screws and studs made of carbon steel or alloy steel
ISO 898-1
Consider property class, dimensions and how much load the design can carry.
Nuts made of carbon steel or alloy steel
ISO 898-2
Proof load and nut hardness are separate testing tasks.
Stainless steel bolts and screws, such as A2/A4
ISO 3506-1
A2-70 and A4-80 follow a different system from 8.8 and 10.9.
Washers, set screws, tapping screws and drilling screws
The relevant product and property standard
Requirements for metric bolts under tensile loading do not automatically apply here.
Which testing method answers which question?
Hardness testing measures how strongly the material resists a test tip or ball pressed into it at a specified location. Tensile and proof load tests examine other mechanical properties; the condition of the specimen or component for these tests is agreed in advance. Torque/clamp force testing examines behaviour during tightening. Fatigue testing shows behaviour under repeated loading. [4]
These methods can complement one another, but answer different questions. If a purchase order calls for “screw testing”, we first clarify what needs to be tested.
Hardness and heat treatment: Vickers, Rockwell or Brinell; separate measurements of the core, surface and hardness profile where required.
Strength requirements in a standard: tests based on the standard that applies to the component, such as tensile or proof load testing.
Assembly and service: the complete joint needs to be examined; hardness measurement alone is not enough.
What type of test report do you need?
State in your enquiry whether measured values for internal assessment are sufficient or a specific inspection document is required. ISO 16228 describes types of inspection documents for fasteners. A laboratory report covering a few hardness measurements is not automatically a complete F3.1 or F3.2 inspection document. [5]
Agree which parts and batches will be tested, which tests are needed and which requirements will be used to assess the results. Results for individual parts do not automatically apply to the whole delivery lot. If the contract requires an accredited report, the laboratory must also be accredited for the specific test method.
What information do we need with your enquiry?
A drawing or photograph and the markings on the parts help with the first discussion. The number of samples needed depends on what will be tested. A comparison at individual measurement locations, an examination of several positions and the inspection of a delivery lot may each need different numbers of samples.
Component type, thread, dimensions and material or property class.
Batch, heat treatment and any coating.
Test objective: incoming inspection, hardness deviation, complaint investigation or verification against a purchase order.
Standard and edition, drawing requirements and the required report type.
Number of available samples and whether the parts may be cut and prepared for testing.
Here, fasteners include bolts, screws, nuts, studs, washers and pins. The tests needed depend on the design, material and intended use.
Is fastener testing the same as screw testing?
Fastener testing is the broader term. Bolt and screw testing is one part of it. Tests for nuts, washers and other components must be selected to suit each type.
Which tests does Testawell perform itself?
We offer Vickers, Rockwell and Brinell hardness testing. We measure in the core, at the surface and along planned series of measurement points on ground and polished sections. We agree the measurement locations and sample preparation with you.
Is Testawell an accredited testing laboratory?
Testawell is currently not accredited to DIN EN ISO/IEC 17025. If you need an accredited test report, arrange the testing in advance with a laboratory accredited for the required method.
Arrange fastener testing for your requirements
Send us the component drawing and details of the material, batch and test objective. We will agree the hardness tests, number of samples and report contents with you.
