How can surface defects in screw fasteners be quickly identified?
2026-03-18
The quality of screw fasteners has always been a top priority for Xin Chun and its customers. While there are specific standards for fastener inspection, some of the inspection procedures can be somewhat cumbersome in practice. So how can we conduct a preliminary inspection of fasteners in a more straightforward manner? In what follows, we will take surface defects in screw fasteners as our starting point and briefly describe several common types of such defects. With a thorough understanding of these defects and practical application, we believe that you will be able to quickly identify substandard fasteners simply by examining their appearance.
The following are the various surface defects and their visual characteristics:
1. Cracks—quenching cracks typically appear on the surfaces of screws and nuts as irregular, intersecting fractures with no discernible orientation.
2. Cracks—Forging cracks—are located on the top surface of bolt and screw heads, as well as on the raised portions of recessed heads.
3. Cracks—Forging Blowouts: These occur on the opposite flat surfaces or diagonals of bolt and screw hex heads, on flange faces or the circumferential surfaces of round-head products, or on raised portions of recessed features.
4. Cracking—Shear Spalling: This type of cracking typically occurs around the circumference of rounded heads or flange faces, usually at an angle of approximately 45° to the product’s axis; it may also appear on the opposite flat surfaces of hexagonal heads.
5. Cracks or longitudinal streaks in the raw material are typically narrow, straight lines or smooth curves that extend longitudinally along the thread, shank, or head.
6. Dent: A shallow pit or depression appearing on the surface of bolts and screws.
7. Wrinkles are folds in the metal that appear on the fastener’s surface.
8. Cut marks: Shallow grooves running longitudinally or circumferentially.
9. Damage, such as dents, scrapes, notches, and chisel grooves. (Mostly caused by collisions during transportation.)
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Address: No. 1, Xinning West Road, Group 6, Ningtong Residence, Jiang’an Town, Rugao City, Jiangsu Province
Nantong Longyu Rail Equipment Co., Ltd.
Contact: General Manager Wu
Address: No. 1, Xinning West Road, Group 6, Ningtong Residence, Jiang’an Town, Rugao City, Jiangsu Province
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