Previous shares on the incoming inspection of bolts were relatively complex and professional, more suitable for warehouse staff with a certain foundation in the hardware industry. However, the fastener industry is quite specialized. Newcomers, especially those who take up warehouse management work right after graduation, often lack relevant knowledge and easily feel confused.
Therefore, this article will analyze several common defects of bolts and matching components, allowing newcomers to quickly identify problems.
First, check the material and surface treatment marks. High-strength bolts (including carbon steel and alloy steel bolts) usually have strength grade marks on their heads-for example, 8.8-grade and 10.9-grade bolts are marked with "8.8" and "10.9" respectively. During inspection, confirm that the marks are clear and consistent with the order requirements. The color of the surface treatment also needs to be verified: carbon steel bolts without surface treatment are mostly iron-gray in their natural color; electrogalvanized bolts are commonly white or blue-white; nickel-plated bolts are usually bright silver (matte nickel plating shows a satin silver color); Dacromet-coated bolts are silver-gray with a distinct gray tone; hot-dip galvanized bolts are silver-gray with a relatively rough and dull surface. If the color does not match the order requirements, or if there are problems such as partial absence of plating or peeling plating, they are all considered defective.
Next, check for common defects on the bolt head, focusing on "crooked head (eccentricity)": the shank of hexagon head bolts should be aligned with the center of the head, the across-flat dimensions of the hexagon head must meet the standards, and the deviation of the three opposite sides should be within the tolerance range without obvious skew. For hexagon socket head bolts, the shank should also be perpendicular to the center of the head, and the head shape should be symmetrical. Special attention should be paid to the hexagon socket-if the socket is eccentric, excessive torque during installation will easily cause uneven force on the head, leading to head breakage. In addition, check the head for cracks, chips, and excessive burrs.
Then, check for common thread defects. Even from qualified suppliers, threads may have problems-do not only focus on stains during inspection: first, check thread integrity, including whether there are damaged threads (broken thread teeth), stripped threads (deformed thread profile that cannot engage properly), or incorrect thread pitch; second, check thread cleanliness. If the threads are attached with oil stains, iron filings left from production, or rust marks, they will not only be difficult to screw together during installation but also affect connection strength. Such uncleaned products should be rejected and returned to the supplier for processing before delivery. A small amount of dust accumulated during packaging usually does not affect use and will fall off naturally during installation.
Finally, check for common defects of flat washers. There are two key inspection points for flat washers: first, thickness-confirm that the thickness meets the standard according to the national standard (GB) model specified in the order (e.g., GB/T 97.1, GB/T 97.2). Taking M12 flat washers as an example, GB/T 97.1 (small washers) specifies a thickness of 1.6mm, while GB/T 97.2 (chamfered flat washers) specifies 2mm-this cannot be generalized. Some merchants use products thinner than the standard to cut costs. Second, appearance-check for excessive burrs, edge notches, and surface warpage. These issues are mostly caused by poor stamping process and worn molds, which will affect installation fit and use safety and should be rejected.
The above are the basic inspection points and common defects of bolts and matching flat washers.
