A threaded insert is a metallic fasteners with an internal or external metric thread that is installed into one member of a fastened joint. A second component can be assembled to it by using a regular metric screw or a nut.
Threaded inserts are usually used in components made of plastic, laminates and wood – which means in soft materials.
- increase the pull-out resistance in plastic parts.
- can make screw assembly easier.
- allow a multiple disassembly and re-assembly during repairs and servicing.
- enable assembly with a regular metric screw in different materials.
- “restore” damaged internal threads.
To assure they are fixed well in a given component, different types of anchoring profiles were developed.
Which type of retaining profile should be used depends on the:
- Material of the component.
- Possible assembly method.
- Needed pull-out resistance.
Low anchoring profile for hard materials
Deep widespaced anchoring profile for soft materials
Assembly of threaded inserts into a given component is carried out as follows:
- by tapping or thread-forming.
- by insertion and expansion.
- by pressing- in (cold, hot, ultrasonically).
- by die-casting and injection-molding.
Assembled threaded insert
A special type of thread insert is the wire thread insert. It is used frequently in aluminum and magnesium to increase the pull-out resistance from the soft material.
Wire thread inserts
It is also very appropriate for the repair of damaged internal threads.
Principally, Bossard recommends the application of thread-forming screws instead of threaded inserts.
- Thread forming screws need less space in the host part.
- There are no costs for buying and assembling the threaded insert.
- Thread forming screws have a better vibration resistance than machine screws in threaded inserts.
Pilot hole for ecosyn®-plast screws instead of a threaded insert
The Bossard proposal as shown in the adjacent figure brought for the customer savings of about US$ 80,000.-/ year.
However, as already above- mentioned, there may be design or assembly circumstances that require threaded inserts. In such cases they are excellent and cost-efficient fasteners.