A thread rolling screw (TRS) is a type of threaded fastener that utilizes threads to reliably and securely fasten different materials. These types of screws create threads in the material by forcing the material outward. As a result, they are most popular in applications where you want to avoid loose chips that are typically created by thread-cutting screws.
What Are They?
Unlike traditional screws, thread rolling screws do not require a pre-tapped hole. As a member of the tapping screw family, these fasteners “roll” or form their own threads by displacing the material instead of removing it. The name “thread rolling screw” is typically reserved for self-tapping screws that have a coarse pitch and a standard machine screw thread form.
What’s the Difference Between a Standard Bolt and a Thread Rolling Screw?
While a standard bolt and thread rolling screw can appear to be similar, there are distinct differences.
Standard M10 Metric Flange Screw
Pictured above is a standard M10 metric flange screw. This type of screw can be threaded into a tapped hole or a mating nut. With this type of screw, make sure to recognize how the lead thread is rounded and uniform.
Thread Rolling Screw
The screws pictured above are both thread rolling screws and will create their own threads into the properly prepared light metal or steel. With thread rolling screws, it’s important to recognize the triangular shape to the point. You should also notice the distinct tapering of the first two to three threads.
The unique tapered lead threads and different shapes are instrumental in helping start rolling threads in the mating material. Although several different point styles can be used with thread rolling screws, they must all meet performance specifications in the corresponding fastener standards such as:
- SAE J1237 or
- DIN 7500
Key Characteristics of Thread Rolling Screws
Thread rolling screws are typically case-hardened. This attribute allows them to create threads into ductile metals that may be up to twice their diameter. The surface hardness of the screw must be harder than the material it’s being threaded into. And thread rolling screws are not ideal for brittle materials, such as cast iron.
Understanding the Fastener Hole
When using thread-forming fasteners, hole preparation is paramount. The hole size can vary based on the thickness and type of material. Because of this, it’s vital to refer to foundational literature, such as the chart below:
You can view this table and other technical literature on the technical section of our website at www.bossard.com.
When creating a pilot hole, the displacement of the material at the entrance of the hole must be taken into consideration. One tip is to add a countersink to the hole, so the bulge isn’t created upon thread forming. The creation of a bulge could result in the parts not seating flat against each other.
Contact Bossard for Thread Rolling Screws
When deciding whether to use thread-rolling screws, it’s important to evaluate the needs of your application. And the engineers at Bossard offer decades of experience providing expert guidance in all matters involving fasteners and thread rolling screws.
For more information on Thread Rolling Screws or any type of fasteners, check out www.bossard.com or contact us at ProvenProductivity@bossard.com.
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