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Description
FINISHED THREADM4 × 0.7
VARIANT3×D (12 mm)
MATERIALStainless steel
SYSTEMV-Coil
M4 3xD thread repair insert – V-Coil DIN 8140 helical thread insert
Thread insert technical data table
| V-COIL M4 3×D THREAD REPAIR INSERT | |
|---|---|
| Restored thread | M4 × 0.7 |
| Thread pitch P | 0.7 mm |
| Length variant | 3×D |
| Insert height | 12 mm |
| Repair system | V-Coil |
| Compatible tap | M4 4H V-Coil |
| Pre-drilled hole | Ø4.1 mm |
The M4x0.7 V-Coil thread repair insert is a coil made from Helicoil-type stainless steel wire. When installed in a hole tapped with a thread repair tap, it creates a fully functional M4 thread for a standard screw. The repair requires neither a larger screw nor replacement of the component. The version 3xD with a height of 12 mm is selected for soft materials and heavily loaded joints. The design complies with DIN 8140 form A (free-running).
M4 thread repair step by step – from the hole to the completed joint
Four installation steps in the V-Coil system
Thread repair process M4 × 0.7
1Prepare the hole
diameter: Ø4.1 mm
2Tap the thread
tool: V-Coil 4H
3Screw in the insert
length: 3×D
✓Restore the joint
thread: M4 × 0.7
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 wire has a diamond-shaped cross section, so it works on both sides simultaneously: the outer edge engages the thread in the hole, while the inner edge forms a new thread for the screw. Before installation, the coil is slightly larger than the hole. As it is screwed in, the coils compress; when the tool is released, they expand and lock permanently in place — without adhesive. The wire has a minimum tensile strength of 1400 MPa — the new thread is harder and smoother than a thread cut directly into the material.
Why a standard M4 tap cannot prepare the insert hole
A pitch of 0.7 mm means a wire thickness of approx. 0.45 mm (the 0.65 × P rule).
The installation thread for the insert is therefore approx. 4.91 mm in diameter — approx. 0.9 mm larger than the nominal 4 mm of an M4 thread.
It can only be prepared with a tap M4 4H V-Coil after drilling Ø4.1 mm; after repair, the screw engages a standard thread M4 × 0.7.
M4 thread repair in steel, stainless steel, cast iron and aluminum
When to choose the 3xD version
The insert restores a damaged M4 thread in steel, stainless steel, cast iron, and aluminum, as well as magnesium and plastics. The 3xD version with a height of 12 mm is suitable for soft materials and screws of property class 8.8 or higher. A shorter version is sufficient for a shallow hole and hard steel. The M4 size is used in applications such as terminals and terminal blocks in electrical equipment. After installation, the first thread turn carries approximately half the force, while the remaining turns carry the rest of 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.
M4 3×D insert compatibility – required V-Coil system tools
Check before purchasing
✓Nominal thread: M4 with a pitch of 0.7 mm.
✓Tap: special M4 4H V-Coil thread repair tap.
✓Tap drill hole: Ø4.1 mm drill bit.
▲Depth: space for an insert 12 mm high and proper seating.
▲
Application limitations
The thread for the insert must be cut with an M4 4H V-Coil STI tap — a nominal M4 thread is too small for the insert to anchor in it. The free-running version does not prevent the bolt from loosening: threadlocker or a screw-locking insert helps under vibration.
After the V-Coil M4 3xD thread repair insert is installed, the screw determines the load limit of the joint, rather than the thread in the part. The hole must accommodate the 12 mm insert (3 × 4 mm), including the correct recess below the surface. In addition to repairs, the insert is suitable for reinforcing threads during manufacture.
Frequently asked questions
The length is selected according to the parent material and screw property class: weaker material and a stronger screw require a longer insert. In steel and cast iron, 1.5xD is sufficient; in aluminum, 2xD is standard; and soft materials and screws of property class 8.8 require 2.5–3xD. This insert has a length of 3xD, or 12 mm after installation.
No, adhesive or additional locking measures are not needed. The coil is larger than the thread in the hole and locks itself permanently in place after installation. Threadlocker is only used under severe vibration; an alternative is a screw-locking insert conforming to DIN 8140 form B.
No, a standard M4 thread with a diameter of 4 mm is approximately 0.9 mm too small. The insert requires an STI thread with a diameter of approximately 4.91 mm. The hole is drilled to Ø4.1 mm and tapped with an M4 4H V-Coil tap.
Yes, the free-running insert is designed for repeated assembly and disassembly. The hard wire with a minimum tensile strength of 1400 MPa does not strip like a soft aluminum thread. Distributing the load across all thread turns protects the thread each time it is tightened.
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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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