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Description
FINISHED THREADM11 × 1.5
VARIANT2.5×D (26 mm)
MATERIALStainless steel
SYSTEMV-Coil
M11 2.5xD thread repair insert – V-Coil DIN 8140 helical thread insert
Thread insert technical data table
| V-COIL M11 2.5×D THREAD REPAIR INSERT | |
|---|---|
| Restored thread | M11 × 1.5 |
| Thread pitch P | 1.5 mm |
| Length variant | 2.5×D |
| Insert height | 26 mm |
| Repair system | V-Coil |
| Compatible tap | M11 4H V-Coil |
| Pre-drilled hole | Ø11.2 mm |
The V-Coil M11x1.5 thread repair insert is a resilient Helicoil-type stainless steel wire coil that restores a damaged thread in its seat. When screwed into a hole tapped with a thread repair tap, it creates a fully functional M11 thread for a standard screw. The repair does not require a larger screw or replacement of the entire part. The 2.5xD version with a height of 26 mm is selected for soft materials and higher property class screws. Insert dimensions are specified by the standard DIN 8140 in form A (free-running).
M11 thread repair step by step – from the hole to the completed joint
Four installation steps in the V-Coil system
Thread repair process M11 × 1.5
1Prepare the hole
diameter: Ø11.2 mm
2Tap the thread
tool: V-Coil 4H
3Screw in the insert
length: 2.5×D
✓Restore the joint
thread: M11 × 1.5
Screw in the insert using an installation tool — do not stretch it or twist it sideways.
Practical installation checks
A clean hole is essential for straightforward installation — remove chips and coolant residue. Install the insert with an installation tool, without forcing or tilting it. The top coil should sit 1/4–1/2 of a turn below the material surface. Break off the tang with a punch; always remove it from a blind hole.
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 M11 tap cannot prepare the insert hole
A pitch of 1.5 mm means a wire thickness of approx. 0.98 mm (the 0.65 × P rule).
The installation thread for the insert is therefore approx. 12.95 mm in diameter — approx. 1.9 mm larger than the nominal 11 mm of an M11 thread.
It can only be prepared with a tap M11 4H V-Coil after drilling Ø11.2 mm; after repair, the screw engages a standard thread M11 × 1.5.
M11 thread repair in steel, stainless steel, cast iron and aluminum
When to choose the 2.5xD version
The insert is suitable for steel, stainless steel, cast iron, and aluminum, as well as magnesium and plastics. The length is selected according to the parent material and screw property class. The version 2.5xD, or 26 mm, distributes the load over more threads. A shorter insert is selected for a shallow hole and hard steel. A longer insert is used in soft material and with bolts of property class 8.8 and higher. The M11x1.5 thread is found in VW and Audi cylinder head bolts, among other applications. The thread load distribution shows that 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.
M11 2.5×D insert compatibility – required V-Coil system tools
Check before purchasing
✓Nominal thread: M11 with a pitch of 1.5 mm.
✓Tap: special M11 4H V-Coil thread repair tap.
✓Tap drill hole: Ø11.2 mm drill bit.
▲Depth: space for an insert 26 mm high and proper seating.
▲
Application limitations
The thread for the insert must be cut with an M11 4H V-Coil STI tap — a nominal M11 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.
A correctly installed V-Coil M11 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 26 mm, or two and a half thread diameters (2.5 × 11 mm). In series production, the same insert serves as preventive reinforcement.
Frequently asked questions
The length is selected according to the parent material and bolt property class. The 1.5xD version is sufficient for steel, cast iron and shallow holes, 2xD is standard for aluminum, and 2.5–3xD is used in soft materials and with bolts of property class 8.8 and higher. This insert is 2.5xD (26 mm).
The top turn of the insert should sit 1/4–1/2 of a turn below the material surface. After installation, the drive tang is broken off with a punch. In a blind hole, the broken piece must be removed.
Yes, insert dimensions are specified by the standard DIN 8140 and ASME B18.29.1. This makes Helicoil, V-Coil, Recoil and BaerCoil interchangeable. The insert size, pitch and length are what matters.
No, this size is used almost exclusively in engines. The M11x1.5 thread is found in the cylinder head bolts of many VW and Audi engines, including 1.8T, 2.0T and 2.8 V6. It is virtually nonexistent outside automotive applications, which makes the availability of an M11 repair tool important.
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All orders are delivered by courier company GLS. For orders exceeding 369 PLN gross shipping is FREE
| 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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