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Description
THREAD BEING REPAIREDM4x0.7
THREAD FOR INSERT4.9 mm
INSERT HEIGHT6.0 mm
NUMBER OF REPAIRS15
M4 thread repair kit – 1.5xD helicoil-type inserts
Kit with drill bit, STI tap, installation tool and 15 inserts
| KIT DATA | |
|---|---|
| Thread to be repaired | M4x0.7 |
| Inserts included | 15 pcs |
| Insert length | 1.5xD = 6.0 mm |
| Drill bit | Ø4.1 mm |
| Tap | STI M4x0.7 HSS-G |
| Insert material | stainless steel |
| Manufacturer | Varel |
| Product code | 13962 |
The M4 thread repair kit restores a stripped threaded hole M4x0.7 without switching to a larger bolt — after repair, the same M4 bolt and the same wrench are used. The kit contains four tools and 15 stainless steel inserts, enough for fifteen holes.
Contents of the M4 thread repair kit
Four tools and a set of inserts in a case
Ø4.1 mm drill bit
HSS, DIN 338 – 1 pcs
M4 STI tap
HSS-G – 1 pcs
M4x0.7 inserts
1.5xD, stainless steel – 15 pcs
Installation tool
tool steel – 1 pcs
Punch
breaks off the tang – 1 pcs
Only the inserts are consumed. The drill bit, tap, installation tool and punch are reusable, so once the inserts in the kit run out, only M4x0.7 1.5xD thread inserts need to be purchased.
Technical data for the STI tap and 1.5xD insert
Dimensions of both kit components
| STI M4x0.7 TAP | |
|---|---|
| Thread to be repaired | M4x0.7 |
| Thread pitch P | 0.7 mm |
| Thread diameter B | 4.9 mm |
| Overall length L1 | 48 mm |
| Flute length | 16 mm |
| Square drive | 4.0 mm |
| Material | HSS-G (ground thread) |
| Tap drill hole | Ø4.1 mm |
| Hole type | through and blind |
| M4x0.7 1.5xD INSERT | |
|---|---|
| Restored thread | M4x0.7 |
| Thread pitch P | 0.7 mm |
| Height after installation | 6.0 mm (1.5xD) |
| Thread count | approximately 6.0 |
| Free-state outside diameter | 5.05–5.6 mm |
| Material | stainless steel |
| Installation version | with tang |
| Recommended drill bit | Ø4.1 mm |
| Thread direction | right-handed |
The 1.5xD inserts supplied in the kit have a universal length suitable for steel, stainless steel, cast iron, and aluminum. Six coils distribute the screw load over the full depth of the tapped hole, while the stainless steel wire separates the steel screw from the aluminum, reducing galvanic corrosion.
How the M4x0.7 thread insert works
Comparison of a directly tapped thread and a thread with an insert
| What changes in the threaded hole | Standard M4 thread | Thread for insert |
|---|---|---|
| Tap drill | 3.3 mm | 4.1 mm |
| Thread cut in the parent material | 4.0 mm | 4.91 mm |
| Tap | M4 | M4 STI |
| Bolt after repair | M4 | M4 |
The insert is a resilient coil made from diamond-section wire, also known in workshops as a thread repair sleeve or spring. The outer edge of the diamond anchors in the oversized thread in the material, while the inner edge provides a standard thread for the screw M4x0.7. The last row of the table says the most: the joint design remains unchanged.
The increase in thread diameter results from the wire thickness. At a pitch of 0.7 mm, the wire measures 0.65 × 0.7 = 0.46 mm, and because it lies on both sides of the profile, the thread in the material increases to 4 + 1.3 × 0.7 = 4.91 mm. This is the diameter cut by the tap M4 STI with a 4.9 mm thread, guided in a hole 4.1 mm.
The insert holds without adhesive. In its free state, it measures 5.05–5.6 mm, larger than the thread in the material. The tool compresses the coils during installation; when torque is released, the coil expands and locks in the tapped hole.
Installing an insert in an M4 hole – sequence of operations
Four steps from drilling to a finished threaded hole
M4 thread repair step by step
1Drilling
Diameter: Ø4.1 mm
2Tapping
Tap: M4 STI
3Screwing in the insert
With the installation tool, a quarter turn below the surface
✓Breaking off the tang
Finished thread: M4x0.7
Tap with oil, reversing the tool after each full turn
▲
The 4.9 mm tap breaks if misaligned
A tool with such a small diameter is unforgiving of angular misalignment. Fit the tap wrench to the 4.0 mm square, check perpendicularity from two sides after the first two turns, and reverse the tap after each full turn to break the chip. A broken tap in an M4 hole usually puts an end to the repair.
In a thin wall, check how much material will remain beneath the hole before drilling. The 1.5xD insert occupies 6 mm, and the 4.1 mm hole must not break through the side of the part.
After breaking off the tang, insert a test screw to the full depth. It should turn in without noticeable resistance — resistance at the first thread indicates that the insert sits too high or has a chip beneath it. A hole fitted with a 1.5xD insert provides six load-bearing threads, as many as a typical M4 joint.
M4 thread repair – customer questions
Selecting tools, drill bit and insert length
Frequently asked questions
No. The insert requires a thread enlarged by twice the wire thickness, or 0.91 mm in diameter. The tap in the kit therefore measures 4.9 mm instead of 4 mm — a thread cut with a standard M4 tap will not support the insert.
Ø4.1 mm, exactly the drill bit supplied in the kit. A standard M4 thread requires a 3.3 mm hole, so the hole for the insert is 0.8 mm larger. A stripped M4 thread usually falls within this allowance.
No, the standard M4 screw is retained. The inside of the insert restores the nominal M4x0.7 thread, so the same screw and tightening torque apply as before the hole was damaged.
Yes, provided the wall is at least 6 mm thick, equal to the height of the 1.5xD insert. In thinner material, the insert projects beyond the thread and loses some of its load-bearing coils — a rivet nut or an extruded hole is then a better solution.
Fifteen — that is the number of inserts in the kit. The tools are reusable, so subsequent repairs cost only as much as the M4x0.7 inserts themselves.
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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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