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Description
FINISHED THREADM20 × 2.5
VARIANT3×D (60 mm)
MATERIALStainless steel
SYSTEMV-Coil
M20 3xD thread repair insert – V-Coil DIN 8140 helical thread insert
Thread insert technical data table
| V-COIL M20 3×D THREAD REPAIR INSERT | |
|---|---|
| Restored thread | M20 × 2.5 |
| Thread pitch P | 2.5 mm |
| Length variant | 3×D |
| Insert height | 60 mm |
| Repair system | V-Coil |
| Compatible tap | M20 4H V-Coil |
| Pre-drilled hole | Ø20.5 mm |
M20 thread repair insert V-Coil is a Helicoil-type stainless steel wire coil. When screwed into a hole tapped with a thread repair tap, it restores a fully functional M20 thread for a standard bolt. It does not require drilling the hole out to a larger size or replacing the entire housing. The 3xD version, with a height of 60 mm, is the longest version, intended for soft materials and heavily loaded joints. Dimensions are specified by DIN 8140 (form A, free-running).
M20 thread repair step by step – from the hole to the completed joint
Four installation steps in the V-Coil system
Thread repair process M20 × 2.5
1Prepare the hole
diameter: Ø20.5 mm
2Tap the thread
tool: V-Coil 4H
3Screw in the insert
length: 3×D
✓Restore the joint
thread: M20 × 2.5
Screw in the insert using an installation tool — do not stretch it or twist it sideways.
Practical installation checks
With a 60 mm insert, drilling perpendicular to the surface is critical — deviation accumulates along the entire thread length. Remove chips and coolant from the hole, and fit the insert with an installation tool without forcing it. The top coil should sit 1/4–1/2 of a turn below the material surface. Break off the tang with a punch; be sure to 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 insert is a resilient helix made from diamond-section wire. The outer edge of the diamond anchors in the oversized 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 once released, 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 needed instead of a standard M20 tap
The wire thickness depends on the thread pitch: 0.65 × 2.5 mm ≈ 1.63 mm.
The thread for the insert is enlarged to accommodate the wire on both sides of the profile — its diameter is approximately 23.25 mm, compared with 20 mm for a standard M20 thread.
It can only be cut with an M20 4H V-Coil thread repair tap in a hole predrilled to Ø20.5 mm; after the insert is installed, the hole returns to the nominal M20 × 2.5 thread.
M20 thread restoration in aluminum, cast iron, and steel structures
When to choose the 3xD version
The insert restores threads in steel, stainless steel, cast iron, and aluminum, as well as magnesium and plastics. The length is selected to suit the parent material and bolt property class. Choose the 3xD version where the material is soft and the bolt is strong: aluminum castings, magnesium alloys, and joints using bolts of property class 8.8 or higher. In steel and cast iron, a shorter 1.5xD insert does the same job, while 2xD is standard for aluminum under moderate loads. The M20 thread carries high forces — it is found in machine frames, gearbox housings, lifting attachments, and hydraulic connections. In a threaded joint, the first thread carries approximately half the force; the table below shows the load distribution.
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.
M20 3×D insert compatibility – required V-Coil system tools
Check before purchasing
✓Nominal thread: M20 with a pitch of 2.5 mm.
✓Tap: special M20 4H V-Coil thread repair tap.
✓Tap drill hole: Ø20.5 mm drill bit.
▲Depth: space for an insert 60 mm high and proper seating.
▲
Application limitations
The thread for the insert must be cut with an M20 4H V-Coil STI tap — a nominal M20 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 M20 3xD V-Coil thread repair insert carries loads so that the bolt shank fails before the thread in the parent material. Plan the hole depth: the insert occupies 60 mm, or three thread diameters (3 × 20 mm). In series production, the same insert provides preventive reinforcement of the threaded hole in the casting.
Frequently asked questions
The length depends on the parent material and bolt property class: the weaker the material and the stronger the bolt, the longer the insert required. The 1.5xD version is suitable for steel, cast iron, and shallow holes, 2xD is standard for aluminum, and 2.5–3xD is suitable for soft materials and bolts of property class 8.8 or higher. This insert is 3×D (60 mm) long.
The insert itself occupies 60 mm. In a blind hole, allow additional depth for tap runout and space for the broken-off tang — in practice, approximately 5 mm, or two thread pitches. Cut the STI thread deeper than the insert length; otherwise, the final coils will not fit.
Yes — insert dimensions are specified by DIN 8140 and ASME B18.29.1, so Helicoil, V-Coil, Recoil, and BaerCoil models are interchangeable. Size, pitch, and length must match.
No — the coil is larger than the thread in the hole and locks itself permanently in place. Threadlocker is only needed under severe vibration; an alternative is a form B screw-locking insert in accordance with DIN 8140.
Product accessories
Drill 20.5 Cobalt NWKc HSSE DIN 345
Reference: 0000008560 In stock < 10 items
€35.53
€43.70 brutto
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| Courier GLS | Cash on delivery | 17,26 zł gross | Lead time 1 working day |
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