Threaded Inserts FAQs

The purpose of this page is to help new or existing customers find the answers to the most often asked questions received by our technical and sales departments.

We'll try and lead you through, from start to finish, how the best threaded inserts are chosen, whether they need to be fitted in plastic, wood or metal, the most suitable method of installation and if you still need help, the best way to contact us.

Wikipedia description - A threaded insert, also known as a threaded bush, 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 threads into a workpiece thereby eliminating a machining operation.

General Questions

Q: What are threaded inserts used for?

A: Threaded inserts are commonly used in plastic casings, housing, and parts to create a metal thread, usually brass, steel or stainless steel, to allow for screws to be used in the assembly of many consumer electronics and consumer products.

Q: Why use threaded inserts?

A: Threaded inserts 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, mould or cast threads into a work piece thereby eliminating a machining operation, or simplify changeover from unified to metric threads or vice-versa.

Q: How do threaded inserts work?

A: Threaded inserts are available in different shapes, which are determined by their use and function. The cylindrical metal shapes, which are placed in holes to provide threaded tracks for bolts and screws, provide extra durability, strength and stability.

Q: What size hole should be used for threaded inserts?

A: As each threaded insert is different, and each screw or bolt that it is being inserted into also differs depending on size and material, each hole will change in size too. Our products all come with a recommended hole size, which is what we advise to ensure that our threaded inserts perform to the highest standard.

Q: How do you choose the best threaded insert?

Q: What type of material is the threaded insert going into?

A: The material (thermoplastic, thermoset, DMC etc) in which the insert will be installed will directly influence the correct choice of insert, the achievable performance and installation method.

Q: What ‘torque’, ‘pull-out’ and ‘jack-out’ performance is required?

A: Torque is the maximum rotating force (Nm) that can be applied to the insert before it ‘spins’ in the moulding. Pull-out performance is the maximum force (Kg), applied in a direct line, that results in the insert being pulled out of the moulding.
Jack-Out is the maximum rotating force (Nm) that can be applied to the insert before it starts to be ‘pulled-out’ of the moulding and occurs when the design of the two mating parts has not been done correctly.

      NOTE: The performance of any insert is directly dependent on the hole size, material and method of installation.

Q: Does the threaded insert need to be ‘headed’ or ‘un-headed’?

A: The majority of threaded inserts we supply are ‘un-headed’ as they are usually installed ‘flush’ into a blind hole. The ‘headed’ style are used in a ‘through hole’ application to prevent them ‘pulling through’. They can also be used in applications where there is an oversize clearance hole in the mating part preventing a ‘jack-out’ situation and for use as an electrical contact.

Q: Choose the appropriate ‘brand’ of threaded insert?

A: Fitsco offer several different types of threaded inserts to suit all types of applications, materials and performance.

Q: What's the best way to install threaded inserts?

A: There are two methods of installing threaded inserts, 'post-moulded' and 'moulded-In'. The three main methods of installing ‘post-moulded’ threaded inserts are using heat or ultrasonics ; cold and screw-in, each method having it's own advantages and disadvantages. The easiest method of installation is to press the threaded inserts in cold. You will get a better performance if the inserts are put in hot using some type of installation machine. The ‘screw-in’ range of inserts has to be installed with specialist equipment and is therefore the hardest to method of installation, but provides the best performance. Moulded-In Installation is the method that provides the maximum performance, but has the disadvantage of requiring the threaded insert to be installed directly into the ‘mould tool’. This method is mainly used in thermoset or DMC mouldings where cycle times are slower, so the time taken to install the threaded inserts is not too much of a disadvantage. The majority of inserts are ‘blind’ stopping plastic material going inside the insert and contaminating the thread.

Q: How do you install threaded inserts in composite or fibreglass?

A: The standard method for thick or cored composite is to epoxy a knurled threaded insert into a small hole. Another method is to tap the hole in the composite and install a self-tapping threaded insert, covering both hole and threaded insert with epoxy. With both types, the insert should be mounted on a greased screw to protect the internal threads from the epoxy. An insert that is bonded will be durable and stronger than a sheet-metal screw inserted straight into the fibreglass, but it is not an effective replacement for a thru-bolt with a backing plate.

Q: How do you install and use threaded inserts in metal?

A: If a threaded insert is being installed in metal, most will require tapping the hole, although there are some types of self-tapping threaded inserts that can be used in soft metals. The taps are usually a special size and thread intended just for the particular insert, which will typically come with the insert as a kit. Coil threaded inserts may also require an insertion tool to tighten the coil.

Q: How do you fit threaded inserts?

A: We are often asked by customers how they should insert their threaded inserts. When screws or bolts are threaded directly into plastic, wood, metal or fibreglass components, failures often occur. Threaded inserts provide stability, strength and durability to the joint. There are several methods of installing threaded inserts, including thermal and ultrasonic, as well as being pressed, moulded and screwed in.

Q: How do you install and use threaded inserts in wood?

A: Threaded inserts which are being installed into wood can be barbed, which are usually pressed or hammered into the hole. Screw threaded inserts will prove to be more durable however. These are typically inserted by spinning, like a wood screw. Some will have a hex socket and are installed with the use of an Allen wrench. Slotted inserts could be installed with a screwdriver, but due to the slot being fragile, the most preferred method is to thread a nut, then the insert, onto a long bolt. The nut should be locked against the insert, then the threaded insert should be turned into the hole with a wrench or socket.

Q: Why use threaded inserts in wood?

A: Threaded inserts will provide strengthening, durability and stability to your products. 

Q: How do you install threaded inserts in plastic?

A: Threaded inserts are typically pressed into plastic with the assistance of heat. A more unorthodox way would be to thread the insert onto a bolt. Use pliers to hold the bolt with the insert in place of the hole, whilst applying pressure downwards. The bolt should be heated with a soldering iron, and as the heat transfers to the insert, which after a minute or so should begin to sink into the softening plastic. Downward pressure should be continued until the threaded insert is at the sought depth, at which point the heat should be removed and hold the bolt steady until the plastic stiffens.

Ready to select the right threaded insert?

Ready to select the right threaded insert?



Choose from the following:



"MultiFit" threaded insert - For 'hot' or 'cold' installation into all types of thermoplastic materials


"HeatFit" threaded insert - For heat or ultrasonic insertion into all types of thermoplastic materials


"Pressfit" threaded insert - For cold installation into both thermoplastic and thermoset materials


"ScrewFit" threaded insert - For 'screw-in' installation into thermoplastic and some thermoset materials


"MouldFit" threaded insert - For 'moulded-in' installation into thermoplastic and thermoset materials


"RotoFit" threaded insert - For 'moulded-in' installation into rotational mouldings

Q: How do you remove threaded inserts?

A: We are often asked if threaded inserts can be removed.  When screws or bolts are repeatedly reinserted into threaded inserts, sometimes the threaded insert needs replacing. With the help of a threaded insert removal tool, the inserts can be removed very quickly.

Firstly, inspect the hole where the threaded insert is located to see how deep and tight it is in the hole. Ensure that it is in the hole, and make sure that it is not flush with the hole, so the insert removal tool can be set on top and remove the threaded insert. Once this is complete, the threaded insert tool needs to be placed and set on top of the threaded insert, lining up the guide shaft with the middle of the hole to decrease the chance of contact between the parent threads and the blade. Attach it in place so that it is secure against the threaded insert, turning the tool anti-clockwise around the threaded insert, simultaneously allowing the blades of the tool to cut grooves into the top coil of the threaded insert. The threaded insert should begin to loosen up and the turning should become less strenuous. Pull up on the threaded insert, whilst still turning it, to remove it from the hole. Check inside the hole to ensure that it is empty, before inserting a new threaded insert.

Still need help?

Still need help?

                . . . . . then please contact our 'help desk' on:

            T: +44 (1) 952 953533 or email: [email protected]

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