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Description
FINISHED THREADM10 × 1.25
VARIANT3×D (30 mm)
MATERIALStainless steel
SYSTEMV-Coil
M10x1.25 3xD thread repair insert – V-Coil DIN 8140 helical thread insert
Thread insert technical data table
| V-COIL M10x1.25 3×D THREAD REPAIR INSERT | |
|---|---|
| Restored thread | M10 × 1.25 |
| Thread pitch P | 1.25 mm |
| Length variant | 3×D |
| Insert height | 30 mm |
| Repair system | V-Coil |
| Compatible tap | M10x1.25 4H V-Coil |
| Pre-drilled hole | Ø10.3 mm |
The M10x1.25 V-Coil thread repair insert is a coil made of Helicoil-type stainless steel wire that is installed in a hole tapped with a thread repair tap. It creates a fully functional M10x1.25 thread for a standard bolt, without a larger bolt or part replacement. The 3xD version, 30 mm high, is selected for soft materials and higher tightening torques. The design conforms to DIN 8140, form A, which is free-running.
M10x1.25 thread repair step by step – from the hole to the completed joint
Four installation steps in the V-Coil system
Thread repair process M10 × 1.25
1Prepare the hole
diameter: Ø10.3 mm
2Tap the thread
tool: V-Coil 4H
3Screw in the insert
length: 3×D
✓Restore the joint
thread: M10 × 1.25
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 M10x1.25 tap cannot prepare the hole
A pitch of 1.25 mm means a wire thickness of approx. 0.81 mm (the 0.65 × P rule).
The installation thread for the insert is therefore approx. 11.62 mm in diameter — approximately 1.6 mm larger than the nominal 10 mm of the M10x1.25 thread.
It can only be prepared with a tap M10x1.25 4H V-Coil after drilling Ø10.3 mm; after repair, the screw engages a standard thread M10 × 1.25.
M10x1.25 thread repair in steel, stainless steel, cast iron and aluminum
When to choose the 3xD version
The insert restores threads equally well in steel, stainless steel, cast iron, and aluminum, as well as magnesium and plastics. The length is selected according to the parent material and bolt property class. The 3xD version is suitable for soft materials and bolts of property class 8.8+, where the longer coil distributes the load across more threads. A shorter version is sufficient in a shallow hole and hard steel. The M10x1.25 size is found in engine bolts, among other applications, where the repair preserves the original tightening torque. After installation the first thread carries approximately half the force, as shown in the load distribution table below.
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.
M10x1.25 3×D insert compatibility – required V-Coil system tools
Check before purchasing
✓Nominal thread: M10x1.25 with a pitch of 1.25 mm.
✓Tap: special M10x1.25 4H V-Coil thread repair tap.
✓Tap drill hole: Ø10.3 mm drill bit.
▲Depth: space for an insert 30 mm high and proper seating.
▲
Application limitations
The thread for the insert must be cut with an M10x1.25 4H V-Coil STI tap — the nominal M10x1.25 thread is too small for the insert to anchor in it. The free-running version does not prevent the screw from loosening: threadlocker or a screw-locking insert helps under vibration.
A correctly installed M10x1.25 3xD V-Coil thread repair insert transfers loads so that the bolt shank fails before the thread in the material. Plan the hole depth: the insert occupies 30 mm, or three thread diameters (3 × 10 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 weaker the material and the stronger the bolt, the longer the insert. The 1.5xD version is sufficient in steel, cast iron, and shallow holes; 2xD is standard for aluminum, while 2.5–3xD is used in soft materials and with bolts of property class 8.8+. This insert has a length of 3×D, equivalent to 30 mm.
No, because the coil is larger than the tapped hole thread and wedges itself permanently in place. Threadlocker is used only under severe vibration. An alternative is a screw-locking insert conforming to DIN 8140, form B.
Yes, insert dimensions are specified by DIN 8140 and ASME B18.29.1, so products from Helicoil, V-Coil, Recoil, and BaerCoil are interchangeable. Size, pitch, and length matter, rather than the manufacturer.
Yes, frequently disassembled threaded holes, such as those for spark plugs or fittings, are typical insert applications. The hard stainless steel wire with a tensile strength of Rm min. 1400 MPa withstands repeated assembly without thread wear. Stainless steel also reduces galvanic corrosion in the aluminum cylinder head.
Product accessories
Thread repair tap M10x1.25 4H V-Coil
Reference: 0000006030 In stock > 10 items
€12.37
€15.21 brutto
Thread repair insert M10x1.25 2xD V-Coil
Reference: 0000007947 In stock > 10 items
€0.47
€0.58 brutto
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Shipping
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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