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Description
FINISHED THREADM14 × 1.25
VARIANT2.5×D (35 mm)
MATERIALStainless steel
SYSTEMV-Coil
M14x1.25 2.5xD thread repair insert – V-Coil DIN 8140 helical thread insert
Thread insert technical data table
| V-COIL M14x1.25 2.5×D THREAD REPAIR INSERT | |
|---|---|
| Restored thread | M14 × 1.25 |
| Thread pitch P | 1.25 mm |
| Length variant | 2.5×D |
| Insert height | 35 mm |
| Repair system | V-Coil |
| Compatible tap | M14x1.25 4H V-Coil |
| Pre-drilled hole | Ø14.3 mm |
The V-Coil M14x1.25 thread repair insert is a resilient Helicoil-type stainless steel wire coil. Installed in a hole tapped with an STI thread repair tap, it restores a fully functional M14x1.25 thread for a standard screw. It repairs the joint without a larger screw or replacement of the entire part. Choose the 2.5xD variant, 35 mm high, for soft materials and screws tightened to higher torque. The insert dimensions are specified by DIN 8140 form A, free-running version.
M14x1.25 thread repair step by step – from the hole to the completed joint
Four installation steps in the V-Coil system
Thread repair process M14 × 1.25
1Prepare the hole
diameter: Ø14.3 mm
2Tap the thread
tool: V-Coil 4H
3Screw in the insert
length: 2.5×D
✓Restore the joint
thread: M14 × 1.25
Screw in the insert using an installation tool — do not stretch it or twist it sideways.
Practical installation checks
Before installation, clean chips and coolant residue out of the hole. Screw in the insert with an installation tool, keeping it straight and using no force. A properly seated insert sits 1/4–1/2 of a turn below the surface. Finally, break off the tang (the crosspiece at the bottom of the insert) with a punch; if the hole is blind, remove the broken piece so that it does not obstruct the screw.
Helicoil-type insert made from diamond-section wire – construction and operating principle
How the insert stays in the hole
The wire has a diamond-shaped cross section: one edge acts as a screw in relation to the hole, and the other as a nut in relation to the screw being installed. The free coil is slightly larger than the thread in the hole; as it is screwed in, it contracts elastically, then expands upon release and locks permanently in place without adhesive or additional components. Cold-rolled wire with a minimum tensile strength of 1400 MPa produces a thread that is harder and smoother than one cut directly into the material.
Why a standard M14x1.25 tap will not work here
The insert wire has a thickness of approx. 0.81 mm (calculated from the thread pitch: 0.65 × 1.25 mm).
The thread for the insert must accommodate the wire on both sides of the profile, so its diameter is approx. 15.62 mm — approximately 1.6 mm larger than a standard M14x1.25 thread (14 mm).
This enlarged thread can only be cut with a thread repair tap M14x1.25 4H V-Coil, after drilling the hole Ø14.3 mm. Once the insert is screwed in, the screw again engages a standard thread M14 × 1.25.
M14x1.25 thread repair in steel, stainless steel, cast iron and aluminum
When to choose the 2.5xD version
The insert restores M14x1.25 threads in steel, stainless steel, cast iron and aluminum, as well as magnesium and plastics. Select the length according to the parent material and screw property class. The variant 2.5xD is suitable for soft materials and screws of property class 8.8 or higher. Choose the shorter 1.5xD insert for steel and shallow holes, and a longer one for more heavily loaded joints. Applications include repairing a stripped spark plug thread in an aluminum cylinder head. The longer coil distributes the load across more thread turns because the first turn carries approximately half the load.
Thread strength: how much load each turn carries
| Thread turn | Standard thread (without an insert) | Thread with a V-Coil insert |
|---|---|---|
| 1 (first from the screw head) | 50% | 30% |
| 2 | 25% | 22% |
| 3 | 12% | 17% |
| 4 | 6% | 13% |
| 5 | 3% | 10% |
| 6 | 2% | 8% |
How to read the table: when the screw is tightened, each thread turn carries part of its load. In a standard thread, the first turn carries as much as 50% of the load — and it strips first. With an insert, the same turn carries only 30% because the load is distributed over the entire thread length. Catalog data from wire thread insert manufacturers.
M14x1.25 2.5×D insert compatibility – required V-Coil system tools
Check before purchasing
✓Nominal thread: M14x1.25 with a pitch of 1.25 mm.
✓Tap: special M14x1.25 4H V-Coil thread repair tap.
✓Tap drill hole: Ø14.3 mm drill bit.
▲Depth: space for an insert 35 mm high and proper seating.
▲
V-Coil system requirements
Installing the insert requires an STI thread — it can only be cut with an M14x1.25 4H V-Coil thread repair tap. The free-running insert allows the screw to be screwed in and out freely; where severe vibration occurs, add threadlocker or choose a screw-locking version.
A properly installed V-Coil M14x1.25 2.5xD thread repair insert carries loads so that the screw shank fails first, rather than the thread in the material. Plan the hole depth: the insert takes up 35 mm, equivalent to two and a half thread diameters (2.5 × 14 mm). In series production, the same insert serves as preventive reinforcement.
Frequently asked questions
The length is selected according to the parent material and screw property class: the weaker the material and the stronger the screw, the longer the insert. The 1.5xD version is suitable for steel and cast iron, 2xD is standard for aluminum, and 2.5–3xD is suitable for soft materials and screws of property class 8.8+. This insert has a length of 2.5xD (35 mm).
No — the coil is larger than the thread in the hole and locks itself permanently in place. Threadlocker is needed only under severe vibration; an alternative is a form B screw-locking insert in accordance with DIN 8140.
Yes — insert dimensions are specified by DIN 8140 and ASME B18.29.1, so Helicoil, V-Coil, Recoil and BaerCoil models are interchangeable. The size, pitch and length must match.
Aluminum has low shear strength, and in a cut thread, the first turn carries approximately 50% of the total load. In addition, the spark plug is removed from its threaded hole during every service, often with the engine hot. The insert distributes the load evenly across successive thread turns.
Product accessories
Thread repair tap M14x1.25 4H V-Coil
Reference: 0000006028 In stock > 10 items
€19.47
€23.95 brutto
Thread repair insert M14x1.25 2xD V-Coil
Reference: 0000007177 In stock > 10 items
€1.05
€1.29 brutto
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| Courier GLS | Przelew24 / Prepayment | 14,76 zł gross | Delivery time 1 working day |
| Courier GLS | Cash on delivery | 17,26 zł gross | Lead time 1 working day |
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