What are the differences and benefits between Thread Rolling and Thread Cutting?
There are two ways of creating threads on mechanical fasteners: rolling or cutting. Sometimes customers ask what is the difference between both? Knowing both processes yield similar results, there are a few differences in each process that cause differences in the products. Before we get into strength of the products, let’s go over the differences between rolled thread and cut thread bolts.
The process of thread rolling a bolt is a cold forming process using a set of hardened steel dies to form threads onto a bolt. The die extends into the outside diameter of the blank bolt to form threads onto the bolt. As the bolt is under high pressure, the steel grain flows in multiple directions, causing the bolt to be stronger, as it does not disturb the structural integrity of the steel. Rolled thread bolts are also smoother in installation and more resistant to damage due to them being hardened and more compressed.
As for thread cutting, it involves severing the steel’s grain structure to produce threads. Rolled thread bolts offer more advantages over cut ones, more specifically strength and cost.
Strength wise, no work is made on the material of thread cut bolts, in alternative, metal removal is used to form the thread. As for rolled thread bolts, the threaded section is formed by metal movement during the cold forming process. This process is what makes the rolled threads stronger.
Thread rolling offers many advantages over thread cutting, mainly a significantly shorter labor times, which mean lower costs. As the threaded bolt has a smaller body.
Rolled threads have improved physical characteristics, great accuracy and a high degree of surface finish than Cut threads. They are uniformly produced at high rates of production with no material waste. These major advantages account for the increased use of thread rolling.
– PHYSICAL CHARACTERISTICS
The cold forging that threads receive during the rolling process strengthens them in tension, shear, and fatigue.
– TENSILE STRENGTH
The cold working of the surface increases the tensile strength of the metal worked, and static tensile test have frequently recorded increases on the order of 10% in the breaking strength of the parts.