As the name suggests, a thread insert is a part that is installed — or inserted — into a workpiece. When properly installed, inserts provide high-quality, wear resistant, permanent internal threads.
In many situations, thread inserts are ideal to repair stripped threads. Thread inserts are also commonly used in new part designs because of the many benefits that they offer. Thread inserts are supplied in a variety of configurations. A tang-free helical insert is installed in much the same way, although instead of using a metal coil tang that has to be removed after installation, tang-free inserts have a drive notch in the helical coil that is used as a grip point for the helical insert tools.
Although both types of helical inserts are used across various industries, the tang-free insert eliminates a step—tang removal—which saves time and money. It also eliminates the need for tang retrieval and the risk of loose metal getting into the machinery. The size of the coil is determined using an STI gauge to match the insert to the hole size. The coil itself is then screwed in place so it presses against the existing screw threads.
Once the coil has been screwed in place, the tang is snapped off so there is no obstruction to the bolt. When the bolt is screwed in place, the helical coil expands inside the drill hole, retaining a locking torque, which creates a firm, lasting connection.
The spring action of the insert is one advantage of using a helical coil. With conventional bolts, more than 75 percent of the load is carried by the first three threads of the assembly.
The helical coil insert transfers shear stress into radial loading over the entire length of the insert. The result is a much stronger bond than you would get with drilling and tapping.
Helical coils are used in various applications, including manufacturing, electrical engineering, aerospace, medical devices, telecommunications, and more. A common example in the automotive industry is repairing an engine cylinder head; often, over-torquing or cross-threading of spark plugs will require a coil to repair the pre-drilled threads.
Because they retain a tight seal, helical coils are particularly useful for gear housings, drills, printing presses, and machinery that generates continuous vibration. In addition to deciding about tanged versus tang-free helical coils, there are other helical insert design choices to consider.
Each type of helical insert is designed for different applications. Free-running helical coils, for example, are extremely flexible inserts designed so that each coil in the helical insert can independently adjust to the fastener threads. This enables more surface contact between the coil and the parent materials, which creates a stronger and more reliable seal because the load is evenly distributed.
The System Thread inserts create high-strength fastenings in low-strength metal materials and have been well established in the market for over 50 years. These stainless steel thread inserts are formed into flexible spirals of proven quality wire with a rhombic profile. After installation, the tang can be broken off at the notch predetermined breaking point to allow through hole threads.
This is a system of high reliability for which German and international industrial property rights have been filed and which is available worldwide. This technology is the basis of national, aeronautical and military standards. A coil thread insert with tang which does not have to be broken off.
Installed quickly and securely — The innovation: The installation mandrel bends it backward during spinning off and then compresses it. As to the Free Running version, thread by thread it is a completely free running coarse thread.
To screw in the thread insert, all you need is the Smart installation mandrel of similar size as a tap. Very special is the blade position control. Simply place it and screw it in like a screw using an installation mandrel with similar dimensions to those of a tap. Existing tools from the previous model can still be used. Installed quickly and securely — and no tang to break.
The innovative coil of the insert allows installation from both ends with identical quality. The spring-mounted installation blade grips into the notch of the coil thread insert and securely installs it in the prepared pilot thread. In addition, the optimised geometry minimises wear on the tools. The tool concept is impressive, boasting long service life for the blades and simple maintenance.
There is a tang, but it does not have to be broken off and removed. The installation time is therefore reduced by approx. Every thread of the thread insert with precision-formed, rhombic profile is free running. The result is a true-to-gauge internal thread including the last thread which is in every case threadable. The thread insert with its precision-formed rhombic profile runs through freely turn for turn. The result is an internal thread that is true to gauge and accepts the insertion of a screw at both ends.
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