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Description
Cutting diameterØ15 mm
Pilot diameterØ6.8 mm
Shank diameterØ12.5 mm
For threadM8
M8 15×6.8 mm counterbore with pilot
Type NWCa · DIN 373 · high-speed steel (HSS) · Artykuly Techniczne brand
Manufactured to DIN 373 15×6.8 mm counterbore with pilot (type NWCa) is used to machine seats for cylindrical screw heads M8 in tap drill holes (Ø6.8 mm — tap drill for M8 threads). Counterboring is performed before tapping, and the pilot keeps the tool precisely aligned with the hole axis. The counterbore made of steel HSS machines steel, aluminum, copper, and brass. A Polish product from the brand Artykuly Techniczne.
| Technical data | |
|---|---|
| Counterbore diameter D | 15 mm |
| Pilot diameter d₁ | 6.8 mm |
| Shank diameter d | 12.5 mm |
| Flute length l | 22 mm |
| Pilot length l₁ | 8 mm |
| Shank length l₂ | 40 mm |
| Overall length L | 100 mm |
| Number of cutting edges Z | 3 |
| For thread | M8 |
| Material | HSS |
| Standard | DIN 373 NWCa |
| Brand | Artykuly Techniczne |
| Country of manufacture | Poland |
Applications and workpiece materials
Applications and materials for the M8 counterbore
Typical applications:
| ✓ | Counterboring seats for cylindrical heads of M8 screws (DIN 912 / ISO 4762) |
| ✓ | Seat machined before tapping the Ø6.8 mm tap drill hole |
| ✓ | Spotfacing around the hole |
| ✓ | Use on CNC machines, drilling machines, and conventional machine tools |
Workpiece materials
✓Structural and carbon steels
✓Copper, brass, bronze
✓Aluminum and light alloys
▲Alloy and stainless steels — with coolant
✗Hardened steels above 45 HRC
Fixed pilot — centering and perpendicularity
Pilot Ø6.8 mm enters the tap drill hole for an M8 thread and guides the tool coaxially — the counterbore remains perpendicular to the hole axis, and after tapping, the screw head makes full surface contact. Steel HSS retains its cutting hardness up to an operating temperature of approx. 600°C.
Cutting data
Guideline values for HSS · Ø15 mm
| Material group (ISO 513) | Vc [m/min] | fz [mm/tooth] | n [rpm] · Ø15 | f [mm/min] · Z=3 |
|---|---|---|---|---|
| PStructural and alloy steel | 5–25 | 0.03–0.10 | 110–530 | 10–160 |
| MStainless steel | 6–15 | 0.03–0.06 | 130–320 | 11–55 |
| KCast iron | 10–20 | 0.08–0.12 | 210–420 | 50–150 |
| NNonferrous metals (Al, Cu, brass) | 15–80 | 0.06–0.14 | 320–1 700 | 55–710 |
| SDifficult-to-machine alloys and titanium | 8 | 0.04 | ≈170 | ≈20 |
Vc — cutting speed, fz — feed per tooth. Columns n and f calculated for D = 15 mm and Z = 3 (rounded). For tools made of steel HSS-E the cutting parameters can be increased by 25%.
How n and f were calculated (Ø15, Z = 3)
Spindle speed n = (Vc × 1000) ÷ (π × D), feed rate per minute f = fz × Z × n. Example for steel (Vc = 20, fz = 0.1): n = 20 000 ÷ 47.1 ≈ 420 rpm, f = 0.1 × 3 × 420 ≈ 130 mm/min. Start at the lower end of the range and adjust according to the material and clamping rigidity.
Tips and limitations
How to extend tool life
HSS limitations
The tool is not intended for hardened steels above 45 HRC. For stainless and alloy steels, reduce the speed and use coolant — overheating accelerates cutting edge wear. Make sure the tap drill hole diameter matches the pilot Ø6.8 mm — counterbore before tapping the hole.
Frequently asked questions
The counterbore produces a flat seat for cylindrical heads of M8 screws, including DIN 912 / ISO 4762 socket head cap screws. The Ø6.8 mm pilot matches the tap drill hole for an M8 thread (Ø6.8 mm drill), so the head seat is machined before tapping the hole. The Ø15 mm counterbore diameter accommodates an M8 socket head cap screw head (Ø13 mm per DIN 912) with a small clearance.
Yes — the tool has a Ø12.5 mm straight shank and fits drill chucks and collets. However, at a diameter of Ø15 mm, low speeds (approx. 110–530 rpm for steel) and rigid workpiece clamping are recommended — preferably a benchtop or pillar drill rather than a handheld drill.
Yes — for ISO M materials (stainless steel), operate at a reduced cutting speed (Vc approx. 6–15 m/min, or approx. 130–320 rpm for Ø15 mm) and use coolant to limit work hardening and overheating. Do not use the tool on hardened steels above 45 HRC.
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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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