Wire thread inserts
Sometimes referred to by the brand names of Helicoil® or Recoil®, helically-coiled wire thread inserts are a thread strengthening fastening device used to create high strength threads in softer core materials. The high performance internal thread provided by our wire inserts is far stronger than most parent materials, and is also heat, corrosion, and wear resistant too.
Manufactured in a huge variety
We manufacture wire inserts in free running and screw locking types in a huge range of sizes and lengths in Metric, Unified, and British Standard thread forms. Made from aircraft quality 304/A2 stainless steel wire, we also stock and supply inserts in a range of alternative materials and finishes, each of which have their own unique benefits. We can also apply colouring to inserts too, which is often requested by customers for identification purposes.
Free Running Inserts
Our standard free running wire thread inserts are produced from Austenitic Stainless Steel wire, which is cold drawn (profiled) to form a diamond-shaped wire. This wire is then helically coiled to produce the wire thread insert.
Larger in diameter than the tapped hole, the insert is compressed during installation to ensure maximum surface contact between the flanks of the wire insert and tapped threads. Once fitted, the action of the radial pressure between the insert’s coils and flanks of the tapped hole holds them in place securely.
The flexibility of our inserts enhances load bearing capacity by deflecting the residual forces into a helical direction, which is dispersed into the wall of the tapped hole.
Screw Locking Inserts
Our screw locking inserts have all of the advantages of a free running type plus the additional benefit of prevailing locking torque, which makes them a valuable and reliable choice for use in applications subject to cyclic vibration or impact.
The locking torque is achieved by the action of a polygonal grip coil in the insert that exerts radial pressure on the male thread, with each grip coil consisting of a number of tangential locking chords that protrude inside the minor diameter of the normal free running coils. As the male thread passes through these grip coils, the locking flats are displaced, thereby exerting radial pressure and prevailing locking torque on the male thread.
On removal of the male thread, the locking coil relaxes to its original form, allowing for repeated assembly whilst retaining a measurable level of prevailing torque.
Note: It is recommended that only close fit plated or lubricated bolts and screws are used with screw locking inserts. Pre-wind tools must be used to install locking inserts.
Materials
304/A2 Stainless Steel
Inserts made from aircraft quality wire that is cold worked in accordance with SAE AS 7245 (equivalent and former specifications include 18/8 Austenitic, DTD 734A, BS EN 2947, and W.NR.1.3401).
- High degree of toughness and hardness
- Excellent corrosion resistance
- Tensile strength up to 1400 N/mm²
- Hardness of RC 43-50
- Withstands temperature range of -200°C to +325°C without detriment to its properties
- Withstands temperature surges up to 425°C.
316/A4 Stainless Steel
Inserts produced in accordance with UNS S31600.
- Good wear resistance
- Superior corrosion resistance when compared to 304/A2 stainless steel
- Particularly suited to applications where there is exposure to galvanic corrosion e.g. marine, saltwater
- Tensile strength up to 1400 N/mm²
- Withstands temperature range of -200°C to +300°C
- Withstands temperature surges up to 425°C.
Phosphor Bronze
Inserts produced from a non-ferrous Copper/Tin alloy in accordance with BS EN 12166 (equivalent specification Wr 2.1020.34).
- Low co-efficient of friction
- Good elastic properties
- Exceptionally resistant to corrosion fatigue
- Anti-galling
- Tensile strength up to 1100 N/mm²
- Particularly useful in applications requiring non-magnetic inserts
- Withstands temperature range of -200°C to +300°C.
Inconel X-750
Inserts produced from precipitation hardened Nickel Chromium alloy in accordance with SAE AS 7246 (equivalent specifications include EN3108 and W.NR.2.4669).
- Especially corrosion resistant
- Tensile strength up to 1600 N/mm²
- Particularly useful in applications requiring non-magnetic inserts
- Withstands temperature range of -200°C to +550°C
- Good creep rupture strength at high temperature surges up to approximately 700°C.
Please note: Inconel X-750 inserts are only available upon special request and minimums may apply.
Nitronic 60®
Inserts manufactured from Austenitic Stainless Steel in accordance with UNS S21800 (equivalent specification SAE AMS 5848). Nitronic 60® is a registered trademark of AK Steel.
- Good corrosion resistance
- Excellent anti-galling
- Excellent wear resistance
- Tensile strength up to 1400 N/mm²
- Withstands temperature range of -200°C to +300°C
- Withstands temperature surges up to +425°C.
Please note: Nitronic 60® inserts are only available upon special request and minimums may apply.
Nimonic 90®
Inserts manufactured from precipitation hardened Nickel Chromium Cobalt alloy in accordance with BS HR503 (equivalent specifications include UNS N07090 and W.NR.2.4632). Nimonic 90® is a registered trademark of Special Metals Corporation.
- High stress rupture strength at elevated temperatures
- Excellent corrosion resistance at high temperatures
- Excellent resistance to oxidation at high temperatures
- Tensile strength up to 1600 N/mm²
- Withstands temperature range of -200°C to +650°C and surges up to 950°C.
Please note: Nimonic 90® inserts are only available upon special request and minimums may apply.
Finishes, platings, and coatings
Cadmium Plate
Inserts with an electrolitically deposited cadmium plating in accordance with SAE AMS 03-19 (formerly DEF STAN 03-19) and AMS-QQ-P-416.
- Excellent barrier between dissimilar metals, reducing the effect of galvanic corrosion
- High lubricity and excellent corrosion resistance prevent seizure and galling between threaded components
- Withstands marine conditions
- Not affected by alkalis
- Suitable for operation in temperatures ranging from -200°C to +235°C.
Zinc Plate
Inserts with an electrolitically deposited Zinc plating in accordance with SAE AMS 03-20 (formerly DTD903).
- Good sacrificial coating for reducing galvanic corrosion
- Provides good corrosion resistance by acting as a barrier and sacrificial coating
- Suitable cost effective alternative to Cadmium plated inserts
- Withstands temperatures ranging from -200°C to +250°C.
Silver Plate
Inserts with an electrolitically deposited Silver plating in accordance with BS EN 2786 and ASTM B700 (formerly DTD939).
- Prevents seizing and galling between threaded components at elevated temperatures
- Widely used in aero-engine applications
- Withstands temperatures ranging from -200°C to +650°C.
Dry Film Lubricant
Inserts with a molybdenum di-sulphide dry film lubricant coating in accordance with MIL-PRF-46010 and SAE AS 5272.
- Prevents seizing and galling between threaded components
- Particularly effective on screw locking inserts
- Withstands temperatures ranging from -100°C to +250°C.
PTFE
Inserts with a solid film heat cured PTFE dry film lubricant coating (Teflon® and Xylan®).
- Lower frictional co-efficient than molybdenum di-sulphide
- Prevents seizing and galling between threaded components
- Available in a range of colours including red, green, and blue
- Withstands temperatures ranging from -100°C to +250°C.
IVD Aluminium
Inserts with an ion vacuum deposited pure Aluminium coating in accordance with MIL-DTL-83488.
- Corrosion resistance superior to Cadmium Plate in most applications
- Uniform film thickness eliminates hydrogen embrittlement
- Withstands temperatures ranging from -200°C to +500°C.
Colourings
At the customer’s request, we are also able to provide wire inserts coloured red, green, and blue. The sold film heat cured colour coating does not affect the insert's performance and is merely an aesthetic choice, typically used as a means of easily identifying between free running and screw locking inserts.
Benefits
Installation procedure
There are six basic stages for installing wire thread inserts:
- Depending upon your application, either drill a new hole, or drill out the damaged thread.
- Tap thread in the hole using a wire insert tap. A standard tap will not provide the correct thread.
- Check the tapped hole using a wire insert gauge.
- Use your tool of choice to install the insert into the hole. Wind the insert until it is positioned approximately 1/4 to 1/2 a pitch below the surface.
- Use a tang break tool or a plain pin punch to break off the tang. Remove the loose tang from the hole.
- Check the installed insert using a thread plug gauge.