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Description
Cutting diameterØ7.5 mm
Pilot diameterØ4.5 mm
Overall length71 mm
Straight shankØ5 mm
7.5×4.5 mm counterbore with pilot
Type NWCa · DIN 373 · high-speed steel (HSS) · Artykuly Techniczne brand
7.5×4.5 mm counterbore with pilot (type NWCa per standard DIN 373) is used to machine predrilled holes Ø4.5 mm — producing a flat, perpendicular seat in them with a diameter of Ø7.5 mm. A size outside the standard screw series is useful for nonstandard heads, spacer washers, and journals. The pilot Ø4.5 mm keeps the counterbore coaxial with the hole. High-speed steel HSS allows machining of steel, cast iron, aluminum, and nonferrous metals. A tool from the Polish brand Artykuly Techniczne.
| Technical data | |
|---|---|
| Counterbore diameter D | 7.5 mm |
| Pilot diameter d₁ | 4.5 mm |
| Shank diameter d | 5 mm |
| Flute length l | 14 mm |
| Pilot length l₁ | 4.5 mm |
| Shank length l₂ | 31.5 mm |
| Overall length L | 71 mm |
| Number of cutting edges Z | 3 |
| Material | HSS |
| Standard | DIN 373 NWCa |
| Brand | Artykuly Techniczne |
| Country of manufacture | Poland |
Applications and workpiece materials
Applications and materials for the 7.5×4.5 mm counterbore
Typical applications:
| ✓ | Flat Ø7.5 mm seats in holes with a diameter of 4.5 mm |
| ✓ | Seats for nonstandard screw heads, washers, and sleeves |
| ✓ | 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 Ø4.5 mm enters a hole with a diameter of 4.5 mm and guides the tool coaxially, keeping the counterbore perpendicular to the hole axis and allowing full surface contact under the screw head. Steel HSS retains its cutting hardness up to an operating temperature of approx. 600°C.
Cutting data
Guideline values for HSS · Ø7.5 mm
| Material group (ISO 513) | Vc [m/min] | fz [mm/tooth] | n [rpm] · Ø7.5 | f [mm/min] · Z=3 |
|---|---|---|---|---|
| PStructural and alloy steel | 5–25 | 0.03–0.10 | 210–1 050 | 19–320 |
| MStainless steel | 6–15 | 0.03–0.06 | 250–640 | 23–110 |
| KCast iron | 10–20 | 0.08–0.12 | 420–850 | 100–310 |
| NNonferrous metals (Al, Cu, brass) | 15–80 | 0.06–0.14 | 640–3 400 | 110–1 430 |
| SDifficult-to-machine alloys and titanium | 8 | 0.04 | ≈340 | ≈40 |
Vc — cutting speed, fz — feed per tooth. Columns n and f calculated for D = 7.5 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 (Ø7.5, 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 ÷ 23.6 ≈ 850 rpm, f = 0.1 × 3 × 850 ≈ 250 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 guide hole diameter matches the pilot Ø4.5 mm.
Frequently asked questions
The Ø4.5 mm pilot guides the tool in a hole with a diameter of 4.5 mm (sliding fit — the hole must not be smaller than the pilot). In this hole, the counterbore machines a flat, perpendicular seat with a diameter of Ø7.5 mm — for example, for a nonstandard screw head, washer, or sleeve.
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. 250–640 rpm for Ø7.5 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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