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Description
Cutting diameterØ8 mm
Pilot diameterØ3.3 mm
Shank diameterØ5 mm
For threadM4
M4 8×3.3 mm counterbore with pilot
Type NWCa · DIN 373 · high-speed steel (HSS) · Artykuly Techniczne brand
M4 8×3.3 mm counterbore with pilot (type NWCa), manufactured to DIN 373, is used to machine seats for cylindrical screw heads M4. The fixed pilot Ø3.3 mm matches the tap drill hole for an M4 thread (Ø3.3 mm drill) — counterboring is performed before tapping, and the pilot guides the tool precisely along the axis of the future thread. As a M4 counterbore for metal performs well in steel, aluminum, copper, and brass. The tool bears the Polish brand Artykuly Techniczne — manufactured in Poland.
| Technical data | |
|---|---|
| Counterbore diameter D | 8 mm |
| Pilot diameter d₁ | 3.3 mm |
| Shank diameter d | 5 mm |
| Flute length l | 14 mm |
| Pilot length l₁ | 4 mm |
| Shank length l₂ | 31.5 mm |
| Overall length L | 71 mm |
| Number of cutting edges Z | 3 |
| For thread | M4 |
| Material | HSS |
| Standard | DIN 373 NWCa |
| Brand | Artykuly Techniczne |
| Country of manufacture | Poland |
Applications and workpiece materials
Applications and materials for the M4 counterbore
Typical applications:
| ✓ | Counterboring seats for cylindrical heads of M4 screws (DIN 912 / ISO 4762) |
| ✓ | Seat machined before tapping the Ø3.3 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 Ø3.3 mm enters the tap drill hole for an M4 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 · Ø8 mm
| Material group (ISO 513) | Vc [m/min] | fz [mm/tooth] | n [rpm] · Ø8 | f [mm/min] · Z=3 |
|---|---|---|---|---|
| PStructural and alloy steel | 5–25 | 0.03–0.10 | 200–990 | 18–300 |
| MStainless steel | 6–15 | 0.03–0.06 | 240–600 | 21–110 |
| KCast iron | 10–20 | 0.08–0.12 | 400–800 | 95–290 |
| NNonferrous metals (Al, Cu, brass) | 15–80 | 0.06–0.14 | 600–3 200 | 110–1 340 |
| SDifficult-to-machine alloys and titanium | 8 | 0.04 | ≈320 | ≈40 |
Vc — cutting speed, fz — feed per tooth. Columns n and f calculated for D = 8 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 (Ø8, 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 ÷ 25.1 ≈ 800 rpm, f = 0.1 × 3 × 800 ≈ 240 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 Ø3.3 mm — counterbore before tapping the hole.
Frequently asked questions
The counterbore produces a flat seat for cylindrical heads of M4 screws, including DIN 912 / ISO 4762 socket head cap screws. The Ø3.3 mm pilot matches the tap drill hole for an M4 thread (Ø3.3 mm drill), so the head seat is machined before tapping the hole. The Ø8 mm counterbore diameter accommodates an M4 socket head cap screw head (Ø7 mm per DIN 912) with a small clearance.
A counterbore (DIN 373) produces a flat-bottomed cylindrical seat for a cylindrical head, such as a socket head cap screw. A countersink (DIN 335) produces a 90° chamfer for a conical/countersunk head. Choose a counterbore for cylindrical head screws and a countersink for countersunk screws.
Yes — for ISO M materials (stainless steel), operate at a reduced cutting speed (Vc approx. 6–15 m/min, or approx. 240–600 rpm for Ø8 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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