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Counterbore 7.5X3.2 DIN 373 HSS
0000009659
Diameter × pilot: 7,5×3.2 mm37 sizes of this countersink
5,5×3.2 mm5,8×2.5 mm6×2.5 mm6×3.2 mm6×3.4 mm7,2×3.2 mm7,5×3.2 mm7,5×4.3 mm7,5×4.5 mm8×3.3 mm8×4.3 mm8×4.5 mm9,5×4.2 mm9,5×5.5 mm10×4.2 mm10×5.3 mm10×5.5 mm10,5×5 mm10,5×6.4 mm10,5×6.5 mm11×5 mm11×6.4 mm11×6.6 mm14×8.4 mm14×9 mm15×6.8 mm15×8.4 mm15×8.5 mm15×9 mm16×9 mm17×11 mm18×8.5 mm18×10.5 mm18×11 mm20×10.2 mm20×13 mm20×14 mm
€10.03 tax inc.
Net price: €8.16
Description
Cutting diameterØ7.5 mm
Pilot diameterØ3.2 mm
Overall length85 mm
Straight shankØ7 mm
7.5×3.2 mm counterbore with pilot
Type NWCa · DIN 373 · high-speed steel (HSS) · Artykuly Techniczne brand
7.5×3.2 mm counterbore with pilot (type NWCa), manufactured to DIN 373, produces flat seats Ø7.5 mm in holes with a diameter of 3.2 mm. This pair of dimensions outside the standard metric screw series is suitable for seats for nonstandard screw heads, washers, sleeves, and locating components. The fixed pilot Ø3.2 mm guides the tool coaxially and prevents the counterbore from drifting sideways in the hole. The tool bears the Polish brand Artykuly Techniczne — manufactured in Poland.
| Technical data | |
|---|---|
| Counterbore diameter D | 7.5 mm |
| Pilot diameter d₁ | 3.2 mm |
| Shank diameter d | 7 mm |
| Flute length l | 12 mm |
| Pilot length l₁ | 6 mm |
| Overall length L | 85 mm |
| Number of cutting edges Z | 4 |
| Material | HSS |
| Standard | DIN 373 NWCa |
| Brand | Artykuly Techniczne |
| Country of manufacture | Poland |
Applications and workpiece materials
Applications and materials for the 7.5×3.2 mm counterbore
Typical applications:
| ✓ | Flat Ø7.5 mm seats in holes with a diameter of 3.2 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 Ø3.2 mm enters a hole with a diameter of 3.2 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=4 |
|---|---|---|---|---|
| PStructural and alloy steel | 5–25 | 0.03–0.10 | 210–1 050 | 25–420 |
| MStainless steel | 6–15 | 0.03–0.06 | 250–640 | 30–150 |
| KCast iron | 10–20 | 0.08–0.12 | 420–850 | 140–410 |
| NNonferrous metals (Al, Cu, brass) | 15–80 | 0.06–0.14 | 640–3 400 | 150–1 900 |
| SDifficult-to-machine alloys and titanium | 8 | 0.04 | ≈340 | ≈55 |
Vc — cutting speed, fz — feed per tooth. Columns n and f calculated for D = 7.5 mm and Z = 4 (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 = 4)
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 × 4 × 850 ≈ 340 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 Ø3.2 mm.
Frequently asked questions
The Ø3.2 mm pilot guides the tool in a hole with a diameter of 3.2 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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