Helicoil-Threaded insert

A thread insert, also known as a threaded bushing, is a fastener element that is inserted into an object to add a threaded hole. They may be used to repair a stripped threaded hole, provide a durable threaded hole in a soft material, place a thread on a material too thin to accept it,mold or cast threads into a workpiece thereby eliminating a machining operation, or simplify changeover from unified to metric threads or vice versa.^[1]

Types

Thread repair inserts come in many varieties, depending on the application.

Captive nut

Captive nuts, also known as insert nuts, are threaded inserts with a knurled base that digs into thin panels. They are used on thin sheet metal that is too thin to be threaded or in soft panels that are too weak to be threaded. They are installed by pressing them in with an arbor press.^[2]

Externally threaded insert

Externally threaded inserts have threads on the outside and inside of the insert. The insert is threaded into a pre-tapped hole, or some inserts tap their own threads in a drilled or molded hole. It is then anchored by various means, such as a nylon locking element. Inserts that are anchored via Loctite are more commonly known by the trademarked name E-Z Loc. A thin walled solid bushing insert by the trademarked name Time-sert is locked in by rolling the bottom few internal thread into the base material with a special install driver which will permanently lock the insert in place.^{[citation needed]} Key locking inserts, more commonly known by the trademarked name Keenserts, use keys that are hammered into grooves through the threads, permanently locking the insert.^[3][4][5] Inserts that are self-tapping and lock via friction are more commonly known by the trademarked names Tap-lok or Speedserts.

Helical insert

Helical inserts, more commonly known by the trademark Heli-coil,^[7] are inserts made of coiled wire. The insert is inserted into a tapped hole that is larger than the desired hole. They are usually over-sized so that they anchor themselves. Some have tangs to install them while others don't. Special tools are required to install the inserts.

Mold-in insert

Mold-in inserts are internally threaded and have a specially shaped outer diameter to anchor the insert in plastic. The insert is placed in the mold of an injection molded part beforehand. The mold is then closed and filled with the plastic filling in around the insert. These inserts can also be heated and pressed into pre-made thermoplastics.

Press fit inserts

Press fit inserts are internally threaded and have a knurled outer diameter. They are pressed into a plain hole with an arbor press.