The ability to conduct strength tests on-site is a huge advantage but, above all, a necessity—one of the most important responsibilities we bear for human safety.
And who knows this responsibility better than those who carry out these tests? Here is the perspective of our Head of Quality Control Department, Robert Sumiński:
“At the company where I work, I am responsible for the final acceptance and approval of products for sale—I handle comprehensive quality control and ensure compliance with dimensional standards or drawing specifications every day. The basis is always dimensional inspection, and I never leave without my caliper and micrometer. In our quality control laboratory, I have a full range of measuring tools allowing me to precisely verify whether the manufactured product meets the required criteria.
Although it might seem that the parts we mostly produce—mainly fasteners like bolts, screws, nuts, and washers—are simple and undemanding, it is worth explaining why, contrary to appearances, the correctness of their manufacture is extremely important. Let’s take a moment to abstract: how many of the things you used today would exist without screws and nuts?
Exactly—these unassuming and common components ensure that most things around us exist and can fulfill their function, thereby making our lives easier every day. This awareness gives me immense motivation to work because I know that although at first glance we make something seemingly ordinary, these items are incredibly important and play a key role in our environment.
This significance is further supported by a great responsibility to ensure, for example, that the devices in which our bolts are installed remain fully functional and safe for the user for as long as possible. Just a ‘small bolt,’ yet it can make a big difference. And the differences in fasteners themselves are huge…
Have you ever seen a bolt marked with numbers like 5.6 or 12.9? Surely you have. But do you know what those mean? Due to different needs, countless types of metal materials are used in the production of fasteners. Most often, this is to match the material’s strength to the ‘work’ the fastener must perform. Sounds odd? Indeed. The word ‘work’ is the most appropriate—the connection of a bolt and a nut in a construction is not just about joining parts together. These components ‘work,’ bearing specific loads related to physical forces acting on them and must function to withstand these forces.
Hence the coding system of letters and numbers—a specific technical shorthand that allows the selection of sufficiently strong fasteners appropriate to the task they must accomplish. So what do A4-80 or 10.9 mean? That is the essence of my work.
According to international standards, A4-80 means an austenitic stainless steel with a minimum tensile strength of 800 megapascals (MPa). Meanwhile, 10.9 is a high-strength steel that can withstand loads of 1 ton per square millimeter, with a yield strength of 900 MPa. In the laboratory, I can perform a static tensile test, which is an effective method to determine the actual strength of the product—i.e., how much ‘work’ a bolt can do without failure.
The static tensile test is one of the fundamental tests used to determine the quality of construction materials based on stress criteria under static load conditions. It allows observation of material behavior across the entire deformation range (elastic, elastoplastic, up to fracture). This test helps determine not only strength but also plasticity characteristics of the material. This destructive test involves stretching the material (in the form of a standardized sample, or for bolts, also in the form of a finished product) in opposite directions until it breaks. Properties determined during the test include tensile strength and yield strength. These two parameters allow us to verify whether a bolt made from a specific metal batch meets the structural load requirements.
Because bolts are mass-produced and ubiquitous, common strength classes have been established to facilitate selection for specific applications.
This test identifies the maximum forces that cause irreversible damage and fracture of the metal, which in real life could lead to catastrophic failure. Therefore, it is also crucial to determine the yield strength—the point at which the material deforms so much that it can no longer return to its original shape. This is the moment when the microscopic bonds in the material break and can no longer hold the original structure. It is the first step toward complete fracture.
Why is identifying this yield point so important? Because it is visually noticeable and serves as a warning. The material does not yet fracture, but it signals what will inevitably happen if forces continue to act. By observing the behavior of the connecting element and noting elongation indicating plastic deformation, this slowly failing part can be replaced in time.
Material plasticity is a kind of safety fuse signaling that the part is worn out and requires replacement. Using established strength class markings guarantees that the right material is used for the functional needs of the structure in which the fastener ‘works.’
Thanks to the tests I perform daily in our in-house quality control laboratory, I am confident that the fasteners we produce are safe for human life.
This awareness gives me great satisfaction, and knowing the importance of my work motivates me to carry out the control process responsibly and thoroughly. I am proud of what I do every day. I also enjoy explaining the specifics of strength testing during practical workshops with students from technical secondary schools in Radom.”