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Description
FINISHED THREADM20 × 2
TOLERANCE4H
PRE-DRILLED HOLEØ20.5 mm
LENGTH L1113 mm
M20x2 thread repair tap – STI tap for V-Coil M20x2 inserts
Tool dimension table and technical data
| V-COIL M20x2 THREAD REPAIR TAP | |
|---|---|
| Thread to be repaired | M20 × 2 |
| 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 M20x2 thread repair tap cuts an STI (Screw Thread Insert) thread for a Helicoil-type insert. The tool restores a load-bearing tapped hole in a damaged housing without increasing the screw size. Once the insert is installed, the hole accepts a standard M20x2 screw again. The 16 mm shank with a 12.5 mm square drive fits common hand tap wrenches and provides reliable guidance along the hole axis.
Repairing stripped M20x2 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. Applications include machine joints with property class 8.8 and 10.9 screws exposed to vibration. The pilot hole is made with a drill bit Ø20.5 mm for the STI tap. Drill at the upper tolerance limit and tap with coolant to produce a clean profile.
The M20x2 thread repair tap cuts an STI thread with dimensions conforming to DIN 8140-2. The tool's overall length L1 is 113 mm, and its flute length L2 is 33 mm. The tool is compatible with V-Coil inserts in lengths of 2xD, and a properly repaired thread carries loads comparable to or greater than the original thread.
Repairing an M20x2 thread step by step
From drilling to the nominal thread
Restoring a thread with an insert is faster and less expensive than replacing the entire housing, for example when a joint is frequently disassembled during maintenance.
Thread repair M20x2 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 × 2
In a blind hole, remove the broken-off tang before installing the screw
M20x2 Helicoil tap (STI) – why it is larger than a standard tap
Compensating for the wire thickness of the thread insert
The STI thread profile remains a metric 60° triangle with a 2 mm pitch — only the size changes. The diameter increases by twice the insert wire thickness: D STI = 20 + 1.3 × 2 = 22.6 mm. This is why the tool's cutting section measures 22.6 mm, and neither an M22 nor an M24 tap can replace it. Class 4H is the metric equivalent of inch class 3B, also recommended for screw-locking inserts. Once the insert is installed, the bolt engages a standard class 6H thread.
Tap compatibility with the V-Coil insert
What must match before starting the repair
✓Matching size: V-Coil M20x2 insert with a 2 mm pitch.
✓Matching hole: prepare a Ø20.5 mm diameter before tapping.
✓Matching version: available M20x2 insert lengths: 2xD.
▲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 solely for installing a V-Coil insert. Use a standard tap to cut a standard M20x2 thread — never to prepare a seat for an insert.
Frequently asked questions
For the STI tap, drill a hole Ø20.5 mm, which is larger than the 18 mm required for a standard M20x2 thread. Drill at the upper tolerance limit so the insert can enter freely. Chamfer the entrance at 90–120°.
No, the STI thread has a nonstandard diameter 22.6 mm and neither standard M22 nor M24 taps can reproduce it. The tool's cutting diameter B is 22.6 mm. An incorrect thread prevents the insert from locking in the hole.
4H is a close fit class for STI threads, corresponding to the inch 3B class used in aerospace and with screw-locking inserts. The close-fitting thread ensures secure seating of the insert. Once installed, the finished thread achieves class 6H.
Yes, the free-running version can be used with threadlocker or a self-locking nut. For severe vibration, form B screw-locking inserts are available according to standard DIN 8140. Their polygonal coil presses against the screw and locks it in the hole.
Product accessories
Drill 20.5 Cobalt NWKc HSSE DIN 345
Reference: 0000008560 In stock < 10 items
€35.53
€43.70 brutto
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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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