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Description
FINISHED THREADM6 × 1
TOLERANCE4H
PRE-DRILLED HOLEØ6.2 mm
LENGTH L172 mm
M6 thread repair tap – STI tap for V-Coil M6x1 inserts
Tool dimension table and technical data
| V-COIL M6 THREAD REPAIR TAP | |
|---|---|
| Thread to be repaired | M6 × 1 |
| Tolerance class | 4H |
| Tap diameter B | 7.3 mm |
| Overall length L1 | 72 mm |
| Flute length L2 | 22 mm |
| Shank diameter D2 | 8 mm |
| Square drive a | 6.3 mm |
| Pre-drilled hole | Ø6.2 mm |
The V-Coil M6 thread repair tap cuts an STI (Screw Thread Insert) thread designed for Helicoil-type inserts. The tool restores a load-bearing seat in a damaged hole without increasing the screw size. Once the insert is installed, the thread accepts a standard M6 screw again without any modifications. The 8 mm shank with a 6.3 mm square drive fits standard hand tap wrenches and helps keep the tap aligned.
Repairing a stripped M6 thread in steel, stainless steel, cast iron, and aluminum
Materials, tips, and limitations
The tool works in steel, stainless steel, cast iron, and aluminum, so one tap serves the entire workshop. Threads strip most often in soft metals, while in steel an insert increases the fatigue life of the joint. An insert can save components such as aluminum housings, where frequent disassembly strips the original thread and the steel wire provides a seat harder than the base material. The pilot hole is drilled to Ø6.2 mm for the STI tap. Drill at the upper tolerance limit and use coolant when tapping to produce a clean thread profile.
The M6 thread repair tap cuts an STI thread with dimensions conforming to DIN 8140-2. The tool's overall length L1 is 72 mm, and its flute length L2 is 22 mm. The tool is compatible with V-Coil inserts in lengths of 2xD, 3xD, and a correctly repaired thread carries loads comparable to or greater than the original thread.
M6 thread repair step by step
From drilling to the nominal thread
Repairing with an insert is faster and less expensive than replacing the entire equipment housing, and the steps below guide you through installation from drilling to the finished threaded seat.
Thread repair M6 with a wire insert
1Drilling
Hole: Ø6.2 mm
2Chamfering the hole entrance
Angle: 90–120°
3STI tapping
With coolant, 4H
4Insert installation
Tang: break off
✓Nominal thread
Screw: M6 × 1
In a blind hole, remove the broken-off tang before installing the screw
Helicoil M6 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 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 = 6 + 1.3 × P = 6 + 1.3 × 1 = 7.3 mm. Therefore, the tool's cutting diameter B is 7.3 mm — a nonstandard value that neither an M7 nor an M8 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 M6 insert with a 1 mm pitch.
✓Matching hole: prepare a Ø6.2 mm diameter before tapping.
✓Matching version: available M6 insert lengths: 2xD, 3xD.
▲Required inspection: depth and wall thickness of the component being repaired.
Tool exclusively for insert threads
The thread cut by this tool is larger than nominal and is intended exclusively for installing a V-Coil insert. Use a standard tap to cut a regular M6 thread — never use it to cut the seat for an insert.
Frequently asked questions
For an STI insert, drill the hole to Ø6.2 mm, rather than 5 mm as for a regular M6 thread. Drill at the upper tolerance limit so the insert fits freely. Chamfer the hole entrance at 90–120° to make starting the tap easier.
No, because the STI thread has a nonstandard diameter 7.3 mm, which neither M7 nor M8 can reproduce. The cutting diameter B of this tool is exactly 7.3 mm. An incorrect thread prevents the insert from locking properly in the hole.
Class 4H provides a close fit for STI threads, equivalent to inch class 3B used in aerospace applications and with screw-locking inserts. The close-fitting thread holds the insert securely. Once the insert is installed, the finished thread meets standard class 6H.
Yes, the free-running insert is designed for repeated assembly and disassembly. The hard wire, with a minimum tensile strength of 1400 MPa, does not strip like a soft thread in aluminum. Distributing the load across all thread turns protects the tapped hole each time the fastener is tightened.
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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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