Helicoil and Fastener Assemblies

Fastener insertion is one of the most critical and essential processes in sheet metal manufacturing, precision mechanics, and the defense industry. It is a process in which components such as nuts, studs, standoffs, and pins are inserted into raw materials, usually sheet metal, by pressing, in order to create strong and durable threads in thin materials that cannot be tapped directly.

Fastener insertion: the precision behind a strong connection

In modern industry, the goal is always to combine maximum strength with minimum weight. Since thin sheet metal does not allow for deep enough threads to withstand loads, fastener insertion technology, sometimes referred to as “PEM technology” after the leading manufacturer, provides the ideal solution.

The importance of precise execution

Fastener insertion is far more than simply “pressing a screw into a hole.” A lack of attention to small details can lead to serious failures:

Torque and pull-out resistance: A fastener that is not inserted correctly may spin in place when the screw is tightened or may be pulled out of the sheet under load.

Damage to sheet flatness: Excessive pressure or mismatch between the fastener and the material may cause deformation or warping of the entire sheet.

Aesthetic considerations: In high-tech and medical industries, the product’s appearance is critical. Poor insertion leaves marks, scratches, or unwanted protrusions.

Electrical conductivity: In electronic products, the fastener may serve as a grounding point. Failure to ensure full and continuous contact can impair the device’s performance.

Material types and compatibility

The material of the fastener must be selected in full compatibility with the base material into which it is inserted:

Carbon steel fasteners: Very common, usually zinc-plated for corrosion protection. Suitable for insertion into steel and aluminum sheets.

Stainless steel fasteners: Used in wet environments or in products requiring high corrosion resistance. Important note: to insert a fastener into stainless steel sheet, the fastener itself must be made of specially hardened stainless steel, such as 400 series, because the inserted material must be harder than the base material.

Aluminum fasteners: Mainly used for weight reduction and where full thermal compatibility with the base material is required.

Insertion method: process steps

The insertion process is usually carried out using dedicated pressing machines, pneumatic or hydraulic, operating under controlled pressure:

Pre-hole creation: This is the most critical stage. The hole must be drilled to the exact diameter specified by the manufacturer, with very tight tolerances. A hole that is too large will cause the fastener to fall out, while a hole that is too small will deform the material.

Selection of the anvil and punch: The correct tools must be used according to the shape of the fastener head to avoid crushing or damage.

Pressing under controlled force: The machine presses the fastener into the hole. Beneath the fastener head there is a groove or knurl. During pressing, the base material flows into this groove, locking the fastener in place and preventing rotation or pull-out.

Quality control: Sample testing of push-out force and torque-out resistance is carried out to ensure the process meets required standards.

Summary

Fastener insertion is a form of engineering craftsmanship. Attention to quality materials, precise tooling, and disciplined workmanship ensures a final product that is strong, reliable, and aesthetically clean. In an industry where every screw matters, the difference between success and failure lies in the small details of the insertion process.

Riveting and rivets: the permanent and powerful connection

Riveting is a process of creating a permanent mechanical connection between two parts, usually sheets or profiles, using a rivet. Unlike a screw, which can be removed, a rivet is intended to create an irreversible joint that will not loosen due to vibration, making it critical in complex engineering structures.

The importance of correct riveting

In riveting, precision is the difference between a stable structure and a safety failure:

Hole filling: A correctly installed rivet must expand and completely fill the hole. If any clearance remains, the rivet will begin to shear under load.

Edge distance: A minimum distance from the sheet edge must be maintained to prevent tearing of the base material.

Clamping pressure: Riveting that is too loose allows moisture penetration and corrosion between the sheets, while excessive pressure may crack brittle materials.

Common types of rivets

Blind / Pop rivet: The most common type in workshops. It allows connection of two parts when access is available from only one side. It consists of a rivet body and a mandrel that is pulled and broken.

Solid rivet: Requires access from both sides. One side has a factory head, while the other side is deformed using a pneumatic hammer or press. These are the rivets used in bridges and aircraft.

Rivet nut / Nutsert: As seen in the previous images you attached, this is a rivet installed into a panel and leaves an internal thread ready for a screw.

Rivet materials

The basic rule in riveting is material compatibility in order to prevent galvanic corrosion, where one metal effectively “eats” the other:

Aluminum: Lightweight and corrosion resistant, mainly used for joining aluminum sheets.

Steel: For joints requiring very high shear strength.

Stainless steel: For marine environments or the food industry.

Copper / brass: For decorative applications or where high electrical conductivity is required.

Installation method for blind riveting

Drilling: Drill a hole with a diameter 0.1–0.2 mm larger than the rivet diameter.

Insertion: Insert the rivet into the hole and position it in the rivet gun.

Pulling: The gun pulls the mandrel. The mandrel head deforms the tail of the rivet on the blind side and clamps the sheets together.

Breaking: When the force reaches its peak, the mandrel breaks at a pre-designed point and is expelled, leaving a tight joint behind.

Guide summary

Press-fit fasteners (PEM): For thin sheets, requires a press.

Rivets: For permanent joints, vibration resistance, and the possibility of working from one side only.

HELICOIL is a precision metal coil used as a strong threaded insert inside soft or damaged materials. It allows restoration of stripped threads or reinforcement of threads in aluminum, magnesium, and plastic. The coil is usually made of stainless steel with a diamond-shaped cross-section, providing high resistance to wear and load. Its installation creates a reliable connection that preserves the original screw dimensions and prevents mechanical failures over time