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Description
FINISHED THREADM2 × 0.4
VARIANT2.5×D (5 mm)
MATERIALStainless steel
SYSTEMV-Coil
M2 2.5xD thread repair insert – V-Coil DIN 8140 helical thread insert
Thread insert technical data table
| V-COIL M2 2.5×D THREAD REPAIR INSERT | |
|---|---|
| Restored thread | M2 × 0.4 |
| Thread pitch P | 0.4 mm |
| Length variant | 2.5×D |
| Insert height | 5 mm |
| Repair system | V-Coil |
| Compatible tap | M2 4H V-Coil |
| Pre-drilled hole | Ø2.1 mm |
The V-Coil M2x0.4 thread repair insert is a Helicoil-type stainless steel wire coil that restores stripped threads in metal and plastic. When screwed into a hole tapped with a thread repair tap, it creates a fully functional M2 thread for a standard screw. It does not require a larger screw or replacement of the entire part. The version 2.5xD with a height of 5 mm is selected for soft materials and higher property class screws. The design complies with DIN 8140, form A (free-running).
M2 thread repair step by step – from the hole to the completed joint
Four installation steps in the V-Coil system
Thread repair process M2 × 0.4
1Prepare the hole
diameter: Ø2.1 mm
2Tap the thread
tool: V-Coil 4H
3Screw in the insert
length: 2.5×D
✓Restore the joint
thread: M2 × 0.4
Screw in the insert using an installation tool — do not stretch it or twist it sideways.
Practical installation checks
After tapping, remove chips and coolant from the hole. Guide the insert with an installation tool without applying pressure — it should screw in easily. The correct depth is 1/4–1/2 of a turn below the material surface. Break off the tang with a punch, and remove the broken piece from a blind hole.
Helicoil-type insert made from diamond-section wire – construction and operating principle
How the insert stays in the hole
The insert is a resilient helix made from diamond-section wire. The outer edge of the diamond anchors in the enlarged thread in the hole, while the inner edge restores the nominal thread for the screw. In its free state, the coil is larger than the hole — installation compresses it, and upon release the coils expand and hold without adhesive. The wire has a minimum tensile strength of 1400 MPa, so the new thread is harder than the original and noticeably smoother.
Why a standard M2 tap cannot prepare the insert hole
A pitch of 0.4 mm means a wire thickness of approx. 0.26 mm (the 0.65 × P rule).
The installation thread for the insert is therefore approx. 2.52 mm in diameter — approx. 0.5 mm larger than the nominal 2 mm of an M2 thread.
It can only be prepared with a tap M2 4H V-Coil after drilling Ø2.1 mm; after repair, the screw engages a standard thread M2 × 0.4.
M2 thread repair in steel, stainless steel, cast iron and aluminum
When to choose the 2.5xD version
The same insert restores M2 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 2.5xD version is suitable for soft materials and screws of property class 8.8 and higher. Choose a shorter insert for a shallow hole and hard steel, and a longer one for soft material. M2 threads are used in small mechanical assemblies, including electronics and RC models. The restored thread distributes the load more evenly, because the first thread carries approximately half the force.
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.
M2 2.5×D insert compatibility – required V-Coil system tools
Check before purchasing
✓Nominal thread: M2 with a pitch of 0.4 mm.
✓Tap: special M2 4H V-Coil thread repair tap.
✓Tap drill hole: Ø2.1 mm drill bit.
▲Depth: space for an insert 5 mm high and proper seating.
▲
What to remember before repair
The insert requires an STI thread cut with a V-Coil system thread repair tap — a standard M2 tap cuts a smaller thread in which the insert cannot be seated. The free-running version does not lock the bolt: for joints exposed to vibration, use threadlocker or a screw-locking insert.
A correctly installed V-Coil M2 2.5xD thread repair insert carries loads such that the screw shank fails before the thread in the material. Plan the hole depth: the insert occupies 5 mm, or two and a half thread diameters (2.5 × 2 mm). In series production, the same insert serves as preventive reinforcement.
Frequently asked questions
Select the length according to the parent material and screw property class: the weaker the material and the stronger the screw, the longer the insert. For steel, cast iron, and shallow holes, 1.5xD is sufficient; for aluminum, 2xD is standard; soft materials and screws of property class 8.8 require 2.5–3xD. This insert has a length of 2.5xD (5 mm).
No, the standard coil is larger than the hole thread and locks itself permanently in place. Use threadlocker only under severe vibration, or choose a form B screw-locking insert in accordance with the standard 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. Thread size, pitch, and insert length must match.
Tighten with a torque screwdriver: the recommended torque is 0.3–0.6 Nm for M2.5, and approximately 0.6–1.0 Nm for M3. A thread restored with an insert is harder than one cut in aluminum because the wire has a minimum tensile strength of 1400 MPa. This allows it to withstand more assembly cycles.
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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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