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Description
FINISHED THREADM18 × 1.5
TOLERANCE4H
PRE-DRILLED HOLEØ18.5 mm
LENGTH L1104 mm
M18x1.5 thread repair tap – STI tap for V-Coil M18x1.5 inserts
Tool dimension table and technical data
| V-COIL M18x1.5 THREAD REPAIR TAP | |
|---|---|
| Thread to be repaired | M18 × 1.5 |
| Tolerance class | 4H |
| Tap diameter B | 20 mm |
| Overall length L1 | 104 mm |
| Flute length L2 | 29 mm |
| Shank diameter D2 | 14 mm |
| Square drive a | 11.2 mm |
| Pre-drilled hole | Ø18.5 mm |
The V-Coil M18x1.5 thread repair tap cuts an STI (Screw Thread Insert) thread for a Helicoil-type insert. The tool restores a load-bearing thread in a damaged hole without increasing the screw size. Once the insert is installed, the hole again accepts a standard M18x1.5 screw, and the joint regains its original size. The 14 mm shank with a 11.2 mm square drive fits typical hand tap wrenches.
Repairing stripped M18x1.5 threads in steel, stainless steel, cast iron, and aluminum
Materials, tips, and limitations
The tool works in steel, stainless steel, cast iron, and aluminum. Threads strip most often in soft metals, while in steel the insert improves the fatigue life of the joint. A typical application is repairing an M18x1.5 oxygen sensor thread damaged while removing a corroded sensor from the exhaust manifold. The hole for the STI tap is made with a drill bit Ø18.5 mm. Drill at the upper tolerance limit and tap with coolant to obtain a clean profile.
The cut STI thread has dimensions conforming to DIN 8140-2, so the M18x1.5 thread repair tap prepares a hole for any insert conforming to this standard — lengths of 1.5xD, 2xD are available in the store. The tool measures 104 mm (L1) with a flute length of 29 mm (L2), and the repaired thread carries loads comparable to or greater than those of the original.
Repairing an M18x1.5 thread step by step
From drilling to the nominal thread
Repairing with an insert is faster and less expensive than replacing the entire exhaust manifold and involves a few simple steps.
Thread repair M18x1.5 with a wire insert
1Drilling
Hole: Ø18.5 mm
2Chamfering the hole entrance
Angle: 90–120°
3STI tapping
With coolant, 4H
4Insert installation
Tang: break off
✓Nominal thread
Screw: M18 × 1.5
In a blind hole, remove the broken-off tang before installing the screw
M18x1.5 Helicoil tap (STI) – why it is larger than a standard tap
Compensating for the wire thickness of the thread insert
The STI tool differs from a standard M18x1.5 tap only in profile size — the 60° angle and 1.5 mm pitch remain metric. The insert wire takes up space on both sides of the profile, so the diameter is D STI = 18 + 1.3 × 1.5 = 19.95 mm; hence the nonstandard 20 mm cutting section, which neither an M20 nor an M22 tap can provide. Tolerance class 4H (equivalent to inch class 3B) is also used for screw-locking inserts, while the finished thread after insert installation is class 6H.
Tap compatibility with the V-Coil insert
What must match before starting the repair
✓Matching size: V-Coil M18x1.5 insert with a 1.5 mm pitch.
✓Matching hole: prepare a Ø18.5 mm diameter before tapping.
✓Matching version: available M18x1.5 insert lengths: 1.5xD, 2xD.
▲Required inspection: depth and wall thickness of the component being repaired.
This is not a substitute for an M18x1.5 tap
The tool cuts only an oversized thread for an insert. A standard M18x1.5 bolt will not engage in a hole tapped this way without an insert, and a standard tap will not prepare the hole for an insert.
Frequently asked questions
For the STI thread, use a drill bit Ø18.5 mm, because the insert requires a larger hole than a standard M18x1.5 thread, for which 16.5 mm is sufficient. Drill at the upper tolerance limit and chamfer the hole entrance at 90–120°.
No, because the STI thread has a nonstandard diameter 19.95 mm, which neither M20 nor M22 can reproduce. An incorrect profile prevents the insert from locking properly. The tool's cutting diameter B is 20 mm.
The designation 4H indicates a close-fit STI thread tolerance class, equivalent to inch thread class 3B used in aerospace and screw-locking inserts. After the insert is installed, the finished thread meets class 6H.
Yes, this is a standard repair. The M18x1.5 thread is restored with an insert after the hole is tapped with an STI tap. Dedicated sensor thread repair kits are listed in the catalogs of insert system manufacturers.
Product accessories
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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Shipping
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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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