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Description
FINISHED THREADM12 × 1.75
TOLERANCE4H
PRE-DRILLED HOLEØ12.4 mm
LENGTH L195 mm
M12 thread repair tap – STI tap for V-Coil M12x1.75 inserts
Tool dimension table and technical data
| V-COIL M12 THREAD REPAIR TAP | |
|---|---|
| Thread to be repaired | M12 × 1.75 |
| Tolerance class | 4H |
| Tap diameter B | 14.3 mm |
| Overall length L1 | 95 mm |
| Flute length L2 | 30 mm |
| Shank diameter D2 | 11.2 mm |
| Square drive a | 9 mm |
| Pre-drilled hole | Ø12.4 mm |
The V-Coil M12 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 M12 screw, without moving to a larger size. The 11.2 mm shank with a 9 mm square drive fits typical hand tap wrenches and allows the tap to be guided by hand.
Repairing a stripped M12 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 it is not limited to a single industry. Threads strip most often in soft metals, while in steel and cast iron the insert also improves the fatigue life of the joint. Repair applications include machine mountings, brackets, and steel and cast iron structures. The hole diameter for the STI tap is Ø12.4 mm. Drill at the upper tolerance limit and tap with coolant to obtain a clean, accurate thread profile.
The M12 thread repair tap cuts an STI thread with dimensions conforming to DIN 8140-2. The tool's overall length L1 is 95 mm, and its flute length L2 is 30 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.
M12 thread repair step by step
From drilling to the nominal thread
Repairing with an insert is faster and less expensive than replacing the entire component, especially for bolted joints frequently disassembled during maintenance.
Thread repair M12 with a wire insert
1Drilling
Hole: Ø12.4 mm
2Chamfering the hole entrance
Angle: 90–120°
3STI tapping
With coolant, 4H
4Insert installation
Tang: break off
✓Nominal thread
Screw: M12 × 1.75
In a blind hole, remove the broken-off tang before installing the screw
Helicoil M12 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 = 1.75 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 = 12 + 1.3 × P = 12 + 1.3 × 1.75 = 14.28 mm. Therefore, the tool's cutting diameter B is 14.3 mm — a nonstandard value that neither an M14 nor an M16 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 M12 insert with a 1.75 mm pitch.
✓Matching hole: prepare a Ø12.4 mm diameter before tapping.
✓Matching version: available M12 insert lengths: 2xD, 3xD.
▲Required inspection: depth and wall thickness of the component being repaired.
This is not a standard M12 tap
The tool prepares an oversized mounting thread for a V-Coil insert. Do not use it to cut a standard M12 thread without an insert, and do not substitute a standard tap for it when installing an insert.
Frequently asked questions
For the STI thread, use a drill bit Ø12.4 mm, rather than 10.2 mm as for a standard M12 thread. Drill at the upper tolerance limit and chamfer the hole entrance at 90–120°.
The STI tap cuts a larger profile with a major diameter of approximately 14.28 mm instead of 12 mm, because it must accommodate two wire thicknesses of 1.14 mm each. The 1.75 mm pitch and 60° angle remain identical. Thanks to DIN 8140, inserts from Helicoil, V-Coil, Recoil, and BaerCoil are interchangeable.
Yes, the inner edge of the wire recreates the nominal M12 × 1.75 thread. The minor diameter after installation is approximately 10.11 mm and conforms to ISO 724. The screw fits without any modifications.
Yes, the same inserts are factory-installed to reinforce threads in cast iron and aluminum. The thread gains the hardness of the wire with a minimum tensile strength of 1400 MPa and uniform load distribution. This also improves the fatigue life of the joint.
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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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