Stainless steel toothless swage nuts are typically made of stainless steel grades such as 304 or 316 to ensure excellent rust and corrosion resistance in various complex environments. They mainly come in two external designs: cylindrical and hexagonal.
Cylindrical swage nuts, coded as ZZS, are suitable for scenarios requiring high surface flatness and compact space. Hexagonal swage nuts, coded as NZNZS, perform well in situations that demand high-torque operation and prevention of nut rotation. The part of both types that is pressed into the sheet metal is cylindrical and has no internal threads. During installation, a dedicated swaging tool is required to tightly rivet the nut to the thin sheet metal through a swaging process, thereby forming a secure connection point on the thin sheet for subsequent matching with fasteners such as bolts.
Although stainless steel toothless swage nuts have no internal threads themselves, they need to be used with external bolts. Therefore, the compatible thread specification determines the inner diameter of the nut. Common compatible metric thread specifications include M3, M4, M5, M6, M8, M10, M12, etc.
Taking the M4 thread as an example: the inner diameter of the matching swage nut should be slightly larger than the outer diameter of the M4 bolt, generally controlled between 4.2-4.3mm with a tolerance range of ±0.05mm. This ensures the bolt can be smoothly screwed in while guaranteeing connection tightness—avoiding loosening caused by excessive clearance or installation difficulties (even thread damage) due to insufficient clearance.
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Cylinder Diameter: The cylinder is a critical part connecting the swage nut to the sheet metal, so its diameter must be precisely matched with the pre-drilled hole in the sheet. For instance, a cylindrical ZZS-type swage nut of M5 specification typically has a cylinder diameter of 7.95-8mm with an allowable deviation of ±0.1mm. If the cylinder diameter is too large, excessive pressure will be exerted on the hole wall of the sheet during swaging, causing the sheet to deform or even crack; if the diameter is too small, insufficient clamping force will be formed between the nut and the sheet after swaging, resulting in an unstable connection.
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Sheet Hole Size: The diameter of the pre-drilled hole in the sheet must be processed strictly according to the cylinder diameter of the swage nut. Generally, the sheet hole diameter is approximately 0.08mm larger than the cylinder diameter. For example, the sheet hole diameter matching the aforementioned M5 swage nut should be 8.03-8.08mm. Meanwhile, the processing tolerance of the sheet hole should be controlled within 0-+0.075mm. A punching process is recommended to ensure the perpendicularity of the hole wall and surface roughness, laying a good foundation for the installation of the swage nut.
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Cylindrical Head Dimensions: For cylindrical ZZS-type swage nuts, there are corresponding standards for head diameter and height. Taking the M6 specification as an example: the head diameter is generally 8.98-9mm, and the height is 6-6.2mm. The head dimensions must ensure tight fitting with the sheet surface after swaging to achieve good surface flatness, while providing a sufficient pressure-bearing area to disperse stress at the connection point.
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Hexagonal Head Dimensions: Hexagonal NZNZS-type swage nuts have clear specifications for the distance across flats (AF), distance across corners (AC), and head height. For example, an M8 hexagonal swage nut has a distance across flats of approximately 10.98-11mm, a distance across corners of about 12.7-12.8mm, and a head height of 6-6.2mm. These dimensions must not only meet the space requirements for wrench operation but also ensure the nut can bear force stably without deformation or slipping during tightening.
The cylinder length of the swage nut should be selected based on the thickness of the connected sheet. Generally, the cylinder length should be 1.5-2mm longer than the sheet thickness. For example, if the sheet thickness is 3mm, a swage nut with a cylinder length of 4.5-5mm should be selected. If the cylinder is too short, an effective riveted structure cannot be formed after swaging, resulting in insufficient connection strength; if the cylinder is too long, the head may protrude or the nut may loosen after swaging, affecting product appearance and connection stability.
In practical production and application, strictly adhering to the dimensional standards of stainless steel toothless swage nuts is key to ensuring product quality.
In the field of electronic device manufacturing—such as the connection of internal structural parts in mobile phones and tablets—due to limited space and high requirements for surface flatness, when using cylindrical stainless steel toothless swage nuts, all dimensions must be precisely controlled to ensure the nut does not affect the overall appearance of the device or internal wiring after installation.
In products with strict corrosion resistance requirements, such as outdoor communication cabinets and medical equipment, when using hexagonal stainless steel toothless swage nuts, appropriate specifications must be selected according to dimensional standards. This ensures connection reliability in long-term complex environments and avoids equipment failures or safety hazards caused by issues like loosening or corrosion due to nut dimensional deviations.
The dimensional standards for stainless steel toothless swage nuts form a rigorous system covering thread compatibility, cylinder-sheet hole matching, head structure, and length compatibility. Whether in design selection or installation operation, strict compliance with these standards is essential to fully leverage their advantages in the industrial fastening field and provide solid guarantees for the quality and safety of various products.
