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Description
FINISHED THREADM18 × 1.5
VARIANT1.5×D (27 mm)
MATERIALStainless steel
SYSTEMV-Coil
M18x1.5 1.5xD thread repair insert – V-Coil DIN 8140 helical thread insert
Thread insert technical data table
| V-COIL M18x1.5 1.5×D THREAD REPAIR INSERT | |
|---|---|
| Restored thread | M18 × 1.5 |
| Thread pitch P | 1.5 mm |
| Length variant | 1.5×D |
| Insert height | 27 mm |
| Repair system | V-Coil |
| Compatible tap | M18x1.5 4H V-Coil |
| Pre-drilled hole | Ø18.5 mm |
The V-Coil M18x1.5 thread repair insert is a resilient Helicoil-type stainless steel wire coil. Installed in a hole tapped with a thread repair tap, it creates a fully functional M18x1.5 thread for a standard screw. The repair requires neither a larger screw nor replacement of the entire part. The 1.5xD version with a height of 27 mm is selected for shallower holes and harder materials. The dimensions comply with DIN 8140 form A, the free-running version.
M18x1.5 thread repair step by step – from the hole to the completed joint
Four installation steps in the V-Coil system
Thread repair process M18 × 1.5
1Prepare the hole
diameter: Ø18.5 mm
2Tap the thread
tool: V-Coil 4H
3Screw in the insert
length: 1.5×D
✓Restore the joint
thread: M18 × 1.5
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 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 an STI tap is required instead of a standard M18x1.5 tap
The wire thickness is determined by the thread pitch: 0.65 × 1.5 mm ≈ 0.98 mm.
The thread for the insert is enlarged to accommodate the wire on both sides of the profile — its diameter is approx. 19.95 mm compared with 18 mm for a standard M18x1.5 thread.
It can only be cut with a thread repair tap M18x1.5 4H V-Coil in a hole drilled to Ø18.5 mm; after the insert is installed, the hole returns to the nominal thread M18 × 1.5.
M18x1.5 thread repair in steel, stainless steel, cast iron and aluminum
When to choose the 1.5xD version
The same M18x1.5 thread can be restored in steel, stainless steel, cast iron, and aluminum. The version 1.5xD with a height of 27 mm is suitable for shallow holes and hard materials such as steel. A shorter insert is selected for a shallow hole in steel, and a longer one for soft material and screws of property class 8.8 or higher. The M18x1.5 thread is a standard size for oxygen sensor ports, among other applications, where repair avoids replacement of the exhaust manifold. Distributing pressure improves engagement between thread turns, since the first turn carries approximately half the assembly 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.
M18x1.5 1.5×D insert compatibility – required V-Coil system tools
Check before purchasing
✓Nominal thread: M18x1.5 with a pitch of 1.5 mm.
✓Tap: special M18x1.5 4H V-Coil thread repair tap.
✓Tap drill hole: Ø18.5 mm drill bit.
▲Depth: space for an insert 27 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 M18x1.5 tap cuts a smaller thread in which the insert will not seat. The free-running version does not lock the screw: use threadlocker or a screw-locking insert for joints exposed to vibration.
A correctly installed V-Coil M18x1.5 1.5xD thread repair insert carries loads so that the screw shank fails before the thread in the material. Plan the hole depth: the insert occupies 27 mm, or one and a half times the thread diameter (1.5 × 18 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. The 1.5xD version is suitable for steel, cast iron, and shallow holes, while 2xD is standard for aluminum. This insert is the 1.5xD version with a height of 27 mm.
The top turn of the insert should sit 1/4 to 1/2 of a turn below the material surface. After installation, break off the installation tang with a punch. In a blind hole, remove the broken fragment before installing the screw.
Yes, because insert dimensions are specified by DIN 8140 and ASME B18.29.1. This makes Helicoil, V-Coil, Recoil, and BaerCoil inserts interchangeable. Matching size, pitch, and length are what matter, for example M18x1.5.
Yes, this is a standard repair: the M18x1.5 thread is restored with an insert after tapping the hole with an STI tap. Insert system manufacturers offer dedicated sensor thread kits in their catalogs. The repair allows the exhaust manifold to be retained.
Product accessories
Thread repair tap M18x1.5 4H V-Coil
Reference: 0000008300 In stock > 10 items
€14.47
€17.80 brutto
HSSE 18.5 cobalt metal drill bit DIN 338
Reference: 13299 In stock > 10 items
€18.42
€22.66 brutto
Thread repair insert M18x1.5 2xD V-Coil
Reference: 0000008302 In stock > 10 items
€1.84
€2.27 brutto
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| Courier GLS | Cash on delivery | 17,26 zł gross | Lead time 1 working day |
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