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Description
Cutting diameter DØ50 H7hole 50.000–50.025 mm
MaterialHSShigh-speed steel (HSS)
StandardDIN 206hand reamer
Number of cutting edgesZ = 12straight flutes
Technical data for the 50 H7 hand reamer
dimensions, standard, and shank specifications
| Technical data | |
|---|---|
| Cutting diameter D | Ø50 H7 · hole 50.000–50.025 mm |
| Hole tolerance zone | H7 (+0.025 / 0 mm) |
| Type | Fixed-size shank-type hand reamer |
| Dimensional standard | DIN 206 |
| Material | HSS (high-speed steel) |
| Flute length l | 174 mm |
| Shank length l₁ | 127 mm |
| Overall length L | 347 mm |
| Number of cutting edges Z | 12 (straight flutes) |
| Shank / drive | Straight shank with square drive (for a tap wrench) |
Hand reamer 50 H7 NRTh — characteristics
construction, operation, and applications
Hand reamer 50 H7 NRTh (DIN 206) is a tool for finishing Ø50 cylindrical holes. Operated by hand, it sizes a drilled hole to 50.000–50.025 mm within tolerance grade H7 — it removes only a thin layer, giving the hole an accurate size, correct roundness and low surface roughness.
The tool is made from high-grade Polish HSS high-speed steel, providing hard, durable cutting edges. The straight flutes accommodate 12 cutting edges; distributing the cut across this many edges improves hole roundness and dampens vibration compared with a two-edge drill. The tapered lead ensures concentricity, while the square drive on the straight shank fits into a tap wrench.
Reaming is classified as finishing, not roughing. A drilled hole falls within IT10–IT11, and the reamer tightens its tolerance to H7, while smoothing the hole wall. Remember that the tool follows the existing hole and will not correct a crooked hole — drill the initial hole perpendicular to the surface. A hand reamer has a longer tapered lead and more cutting edges than a machine reamer, making even cutting easier with manual feed. The tool facilitates fitting holes for plain bearing bushings, where tolerance grade H7 determines the correct fit and operation of the assembly.
H7 tolerance and Ø50 hole accuracy
final tolerance zone of the machined hole
Ø50 mm hole size by tolerance grade (ISO 286)
| Designation | Hole Ø range [mm] | Deviations [mm] | IT tolerance grade |
|---|---|---|---|
| 50 H6 | 50.000 – 50.016 | +0.016 / 0 | 16 µm |
| 50 H7 | 50.000 – 50.025 | +0.025 / 0 | 25 µm this product |
| 50 H8 | 50.000 – 50.039 | +0.039 / 0 | 39 µm |
| 50 H9 | 50.000 – 50.062 | +0.062 / 0 | 62 µm |
| 50 H11 | 50.000 – 50.160 | +0.160 / 0 | 160 µm |
Your reamer produces tolerance grade H7 — finished hole Ø50.000–50.025 mm; the value is stated directly, without conversion from tables. A narrower tolerance zone means a more accurate hole. The reamed surface is smooth — typically Ra 0.4–1.6 µm, significantly better than after drilling alone (approx. 1.6–3.2 µm).
Manual machining — how to ream Ø50 H7
tap wrench operation, allowance and predrilled hole
The reamer is operated by hand, with a tap wrench fitted over the square drive on the shank and turned with an even, steady motion in one direction. For Ø50 H7, leave a 0.4–0.5 mm allowance on diameter: in practice, drill Ø49.5 mm, and remove the remaining stock with a reamer. The larger diameter requires a sturdy tap wrench and more torque — guide the tool steadily. Apply plenty of cutting oil — generous lubrication reduces resistance and provides a surface finish of Ra 0.4–1.6 µm, whereas drilling leaves approx. 1.6–3.2 µm.
▲Important: is a tool for manual machining — it is not intended for powered operation at high speeds. High-speed steel loses hardness above approx. 600 °C, so lubricate generously. Do not stop the reamer in the hole or reverse rotation — always withdraw it while continuing to rotate forward; withdrawing without rotation risks chip jamming, chipped cutting edges and a poorer hole finish.
Applications — workpiece materials
groups P1.2–P1.3 according to the material classification
✓Unalloyed and structural steel
✓Free-machining steel
✓Nonferrous metals — brass, bronze, copper
✓Light alloys and soft metals
▲Alloy steel — possible with generous lubrication and low speeds
✗Hardened steel and hardened stainless steel — beyond the capabilities of HSS
Frequently asked questions
It is suitable for unalloyed and free-machining steels, brass, bronze, copper and light alloys (P1.2–P1.3). When machining alloy steel, work slowly and lubricate generously. Hardened steel and hardened stainless steel are beyond the capabilities of an HSS tool.
H7 for Ø50 is 50.000–50.025 mm (+0.025 / 0 mm) — a narrower tolerance zone than H8 and H9, making the hole more accurate. A narrower tolerance means a tighter, more repeatable fit. The surface finish after reaming is Ra 0.4–1.6 µm.
Leave a stock allowance of 0.4–0.5 mm on the diameter. In practice, drill the pilot hole with a Ø49.5 mm drill, then hand-ream to the final size, lubricating generously with cutting oil.
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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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