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Description
FINISHED THREADM20 × 1.5
TOLERANCE4H
PRE-DRILLED HOLEØ20.5 mm
LENGTH L1113 mm
M20x1.5 thread repair tap – STI tap for V-Coil M20x1.5 inserts
Tool dimension table and technical data
| V-COIL M20x1.5 THREAD REPAIR TAP | |
|---|---|
| Thread to be repaired | M20 × 1.5 |
| Tolerance class | 4H |
| Tap diameter B | 22.6 mm |
| Overall length L1 | 113 mm |
| Flute length L2 | 33 mm |
| Shank diameter D2 | 16 mm |
| Square drive a | 12.5 mm |
| Pre-drilled hole | Ø20.5 mm |
The V-Coil M20x1.5 thread repair tap cuts a seat for a Helicoil-type insert and creates an STI (Screw Thread Insert) thread with an enlarged profile. The tool restores a load-bearing seat in a damaged component without increasing the screw size itself. Once the insert is installed, the hole accepts a standard M20x1.5 screw again. The 16 mm diameter shank with a 12.5 mm square drive fits standard hand tap wrenches.
Repairing stripped M20x1.5 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 frequently in soft metals, while in steel the insert increases the fatigue life of the joint. M20x1.5 threads are found in drain plugs on older engines and near exhaust system sensor ports, among other applications. The hole is predrilled to a diameter of Ø20.5 mm for the STI tap. Drill at the upper tolerance limit and use coolant when tapping to produce a clean thread profile.
The dimensions of the cut STI thread are specified by DIN 8140-2. The M20x1.5 thread repair tap has an overall length L1 of 113 mm and a flute length L2 of 33 mm, and is compatible with V-Coil inserts in lengths of 1.5xD and 2xD. A correctly installed insert restores a thread with a load capacity comparable to or greater than the original.
Repairing an M20x1.5 thread step by step
From drilling to the nominal thread
Repairing a thread with an insert is faster and less expensive than replacing the entire manifold or drain plug, and involves a few steps.
Thread repair M20x1.5 with a wire insert
1Drilling
Hole: Ø20.5 mm
2Chamfering the hole entrance
Angle: 90–120°
3STI tapping
With coolant, 4H
4Insert installation
Tang: break off
✓Nominal thread
Screw: M20 × 1.5
In a blind hole, remove the broken-off tang before installing the screw
M20x1.5 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 M20x1.5 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 = 20 + 1.3 × 1.5 = 21.95 mm; hence the nonstandard 22.6 mm cutting section, which neither an M22 nor an M24 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 M20x1.5 insert with a 1.5 mm pitch.
✓Matching hole: prepare a Ø20.5 mm diameter before tapping.
✓Matching version: available M20x1.5 insert lengths: 1.5xD, 2xD.
▲Required inspection: depth and wall thickness of the component being repaired.
This is not a standard M20x1.5 tap
The tool prepares an oversized mounting thread for a V-Coil insert. Do not use it to cut a standard M20x1.5 thread without an insert, and do not substitute a standard tap for it when installing an insert.
Frequently asked questions
The hole for the STI tap is drilled to a diameter of Ø20.5 mm, rather than 18.5 mm as for a standard M20x1.5 thread. Drill at the upper tolerance limit so the insert fits freely. Chamfer the entrance at 90–120°.
No. The STI thread has a nonstandard diameter of 21.95 mm that neither an M22 nor an M24 tap can reproduce. An incorrect thread profile prevents the insert from locking in its seat. The cutting diameter of this tool is B = 22.6 mm.
Yes. The inner edge of the insert wire restores the nominal M20 × 1.5 thread, allowing a standard screw to be installed without modification. The minor diameter after installation is approximately 18.38 mm, in accordance with ISO 724.
Yes, this is a standard repair without removing the manifold. The seat is tapped with an STI tap, and the insert restores the M18x1.5 thread. Sensor thread repair kits are catalog items offered by insert system manufacturers.
Product accessories
Drill 20.5 Cobalt NWKc HSSE DIN 345
Reference: 0000008560 In stock < 10 items
€35.53
€43.70 brutto
Thread repair insert M20x1.5 2xD V-Coil
Reference: 0000010715 In stock > 10 items
€1.97
€2.43 brutto
Thread repair insert M20x1.5 1.5xD V-Coil
Reference: 0000010797 In stock < 10 items
€2.08
€2.56 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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