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Description
FINISHED THREADM10 × 1.5
TOLERANCE4H
PRE-DRILLED HOLEØ10.3 mm
LENGTH L189 mm
M10 thread repair tap – STI tap for V-Coil M10x1.5 inserts
Tool dimension table and technical data
| V-COIL M10 THREAD REPAIR TAP | |
|---|---|
| Thread to be repaired | M10 × 1.5 |
| Tolerance class | 4H |
| Tap diameter B | 11.9 mm |
| Overall length L1 | 89 mm |
| Flute length L2 | 29 mm |
| Shank diameter D2 | 9 mm |
| Square drive a | 7.1 mm |
| Pre-drilled hole | Ø10.3 mm |
The V-Coil M10 thread repair tap cuts an STI (Screw Thread Insert) thread for a Helicoil-type M10x1.5 wire thread insert. The tool restores a load-bearing seat where the thread has stripped without increasing the bolt size — once the insert is installed, the hole again accepts a standard M10 bolt. The 9 mm diameter shank with a square drive measuring 7.1 mm across flats fits standard hand tap wrenches.
Repairing stripped M10 threads in aluminum, cast iron, and steel
Materials, tips, and limitations
The tap for M10x1.5 thread inserts is most often used in materials with low shear strength: aluminum alloys, magnesium alloys, and cast iron, where a directly cut thread pulls out under load. It is also suitable for repairing M10 threads in steel — the resilient insert evens out the load distribution across the thread turns and improves the fatigue life of the joint. The recommended hole size for the STI tap is Ø10.3 mm; drill near the upper tolerance limit and tap with coolant, periodically reversing the tool to break the chip.
The M10 thread repair tap cuts an STI thread with dimensions conforming to DIN 8140-2. The tool's overall length L1 is 89 mm, and its flute length L2 is 29 mm. The tool is compatible with V-Coil inserts in lengths from 1.5xD to 3xD, and a properly repaired thread carries loads comparable to or greater than the original thread.
M10 thread repair step by step
From drilling to the nominal thread
Repairing an M10 thread with a V-Coil insert takes a little over ten minutes and does not require replacing the damaged component, such as an engine block or gearbox housing.
Thread repair M10 with a wire insert
1Drilling
Hole: Ø10.3 mm
2Chamfering the hole entrance
Angle: 90–120°
3STI tapping
With coolant, 4H
4Insert installation
Tang: break off
✓Nominal thread
Screw: M10 × 1.5
In a blind hole, remove the broken-off tang before installing the screw
Helicoil M10 tap (STI) – why it is larger than a standard tap
Compensating for the wire thickness of the thread insert
The STI thread retains the pitch P = 1.5 mm and the 60° thread angle of the ISO metric thread, but its diameter is intentionally enlarged. The increase compensates for the insert wire thickness on both sides of the profile, according to the following relationship: D STI = 10 + 1.3 × P = 10 + 1.3 × 1.5 = 11.95 mm. Therefore, the tool's cutting diameter B is 11.9 mm — a nonstandard value that neither an M11 nor an M12 tap can provide. The 4H tolerance corresponds to inch thread class 3B and is also suitable for screw-locking inserts; once the insert is installed, the finished thread achieves the standard 6H class.
Tap compatibility with the V-Coil insert
What must match before starting the repair
✓Matching size: V-Coil M10 insert with a 1.5 mm pitch.
✓Matching hole: prepare a Ø10.3 mm diameter before tapping.
✓Matching version: the 3×D insert has a height of 30 mm.
▲Required inspection: depth and wall thickness of the component being repaired.
This is not a standard M10 tap
The tool prepares an oversized mounting thread for a V-Coil insert. Do not use it to cut a standard M10 thread without an insert, and do not substitute a standard tap for it when installing an insert.
Frequently asked questions
The STI tap cuts a thread with a major diameter of approximately 11.95 mm instead of 10 mm — the increase corresponds to twice the insert wire thickness. The 1.5 mm pitch and 60° profile angle remain identical, so a standard M10 bolt fits only after the insert is installed. Inserts from different brands — Helicoil, V-Coil, Recoil, BaerCoil — are interchangeable because their dimensions are specified by DIN 8140.
The recommended pilot hole size is 10.3 mm — significantly larger than the 8.5 mm for a standard M10 thread, because the hole must accommodate the insert wire thickness. Drill near the upper tolerance limit and chamfer the entrance at 90–120°.
4H is a close-fit class for STI threads, equivalent to inch class 3B recommended for aerospace applications and screw-locking inserts. Once the insert is installed, the finished thread meets standard class 6H.
Yes. The inner edge of the insert wire restores the nominal M10 × 1.5 thread — the minor diameter after installation is approximately 8.38 mm, almost identical to the 8.376 mm of an ISO 724 thread. The bolt requires no modifications.
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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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