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Description
FINISHED THREADM9 × 1.25
VARIANT2×D (18 mm)
MATERIALStainless steel
SYSTEMV-Coil
M9x1.25 2xD thread repair insert – V-Coil DIN 8140 helical thread insert
Thread insert technical data table
| V-COIL M9x1.25 2×D THREAD REPAIR INSERT | |
|---|---|
| Restored thread | M9 × 1.25 |
| Thread pitch P | 1.25 mm |
| Length variant | 2×D |
| Insert height | 18 mm |
| Repair system | V-Coil |
| Compatible tap | M9x1.25 4H V-Coil |
| Pre-drilled hole | Ø9.3 mm |
The V-Coil M9x1.25 thread repair insert restores a damaged thread using Helicoil-type stainless steel wire. Installed in a hole tapped with a thread repair tap, it creates a fully functional M9x1.25 thread for a standard screw. There is no need for a larger screw or replacement of the entire part. Select the 2xD version with a height of 18 mm for standard holes and typical loads. The dimensions comply with DIN 8140 form A, the free-running version.
M9x1.25 thread repair step by step – from the hole to the completed joint
Four installation steps in the V-Coil system
Thread repair process M9 × 1.25
1Prepare the hole
diameter: Ø9.3 mm
2Tap the thread
tool: V-Coil 4H
3Screw in the insert
length: 2×D
✓Restore the joint
thread: M9 × 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 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 M9x1.25 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. 10.62 mm in diameter — approximately 1.6 mm larger than the nominal 9 mm of the M9x1.25 thread.
It can only be prepared with a tap M9x1.25 4H V-Coil after drilling Ø9.3 mm; after repair, the screw engages a standard thread M9 × 1.25.
M9x1.25 thread repair in steel, stainless steel, cast iron and aluminum
When to choose the 2xD version
The same insert restores an M9x1.25 thread 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 version 2xD is suitable for typical conditions. Select a shorter version for a shallow hole in steel and a longer one for soft material and screws of property class 8.8 or higher. The M9x1.25 size may be needed, for example, when repairing unusual older designs. After installation, the first thread turn carries approximately half the force, as shown in the load distribution table.
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.
M9x1.25 2×D insert compatibility – required V-Coil system tools
Check before purchasing
✓Nominal thread: M9x1.25 with a pitch of 1.25 mm.
✓Tap: special M9x1.25 4H V-Coil thread repair tap.
✓Tap drill hole: Ø9.3 mm drill bit.
▲Depth: space for an insert 18 mm high and proper seating.
▲
Application limitations
The thread for the insert must be cut with an M9x1.25 4H V-Coil STI tap — the nominal M9x1.25 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.
After installation of the V-Coil M9x1.25 2xD thread repair insert, the screw determines the joint's load limit, rather than the thread in the part. The hole must accommodate the 18 mm insert (2 × 9 mm) along with the proper recess below the surface. In addition to repairs, the insert is suitable for reinforcing threads during manufacturing.
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. In steel, cast iron, and shallow holes, 1.5xD is sufficient; 2xD is standard for aluminum, while soft materials and screws of property class 8.8+ require 2.5–3xD. This insert has a length of 2×D, equivalent to 18 mm.
No — the coil is larger than the tapped hole and locks itself permanently in place. Use threadlocker only under severe vibration, or alternatively select a DIN 8140 form B screw-locking insert.
Yes — insert dimensions are specified by DIN 8140 and ASME B18.29.1, so Helicoil, V-Coil, Recoil, and BaerCoil are interchangeable. Matching size, pitch, and length are what matter.
After the insert is installed, the thread returns to its nominal M9x1.25 size, so the existing screw fits. Screws of this size are available from fastener distributors as a special size.
Product accessories
Thread repair tap M9x1.25 4H V-Coil
Reference: 0000005933 In stock > 10 items
€10.53
€12.95 brutto
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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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