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Description
Diameter D Ø8 mm
Tolerance H78.000–8.015 mm
Standard DIN 212
Material HSSE
Machine reamer Ø8 H7 for metal — technical data
NRTd — shank-type finishing reamer, straight shank, HSSE DIN 212
| Technical Data | |
|---|---|
| Cutting diameter D | Ø8 H7 (8.000–8.015 mm) |
| Shank diameter (d9) | 8 mm |
| Flute length l | 33 mm |
| Shank length l₁ | 42 mm |
| Overall length L | 117 mm |
| Number of teeth Z | 6 |
| Type | NRTd — shank-type finishing reamer, straight shank |
| Dimensional standard | DIN 212 |
| Material | HSSE (cobalt high-speed steel) |
What H7 tolerance means for a diameter of 8 mm
| Class | Deviations [mm] | Dimension [mm] | |
|---|---|---|---|
| H6 | +0.009 / 0 | 8.000 – 8.009 | |
| H7 | +0.015 / 0 | 8.000 – 8.015 | SELECTED |
| H8 | +0.022 / 0 | 8.000 – 8.022 | |
| H9 | +0.036 / 0 | 8.000 – 8.036 |
The reamed hole falls within the tolerance zone 8.000–8.015 mm (ISO 286-2) — an accuracy level typical of dowel pin holes and sliding fits, among other applications.
Cutting data for the machine reamer Ø8 H7
Indicative values Ø8 mm Z = 6
| Material group (ISO 513) | Vc [m/min] | fz [mm/tooth] | n [rpm] Ø8 | f [mm/min] Z=6 |
|---|---|---|---|---|
| PStructural and carbon steel | 8–10 | 0.08–0.12 | 318 | 153 |
| MStainless steel | 2–3 | 0.08–0.12 | 80 | 38 |
| KCast iron | 3–5 | 0.10–0.14 | 119 | 71 |
| NAluminum and light alloys | 12–16 | 0.12–0.16 | 477 | 343 |
Vc — cutting speed, fz — feed per tooth (catalog values for HSS, selected for a diameter of Ø8 mm). Spindle speeds were calculated for the lower end of the range: n = (Vc × 1000) ÷ (π × D), feed rate per minute f = fz × Z × n for Z = 6. Start with the lower values and adjust according to the material and clamping rigidity. For an HSSE (cobalt) reamer, the cutting parameters can be increased by approx. 25% compared with HSS.
You may also need: Cutting parameters calculator
Applications of the machine reamer Ø8 H7 for metal
Hole finishing to H7 tolerance
Machine reamer Ø8 H7 for metal — NRTd shank-type finishing reamer with straight shank according to DIN 212, made of cobalt high-speed steel HSSE (approx. 5% Co). Used for finishing holes — from drill presses to CNC machining centers. The tool has a ~45° lead-in chamfer at the tip for centered entry, while the guiding margins on the cutting edges keep the tool aligned with the hole axis.
The Ø8 H7 reamer for metal removes the stock left after drilling and brings the hole to its final size within the tolerance zone H7 (8.000–8.015 mm). Reaming straightens the hole axis, improves roundness and cylindricity, and reduces surface roughness to approx. Ra 0.4–1.6 µm. 6 unequally spaced cutting edges reduce vibration and machining marks. This diameter range is commonly used for sliding fits: pins, shafts, plain bushings, and dowel pin holes in housings. Suitable for reaming steel, cast iron, and nonferrous metals — the addition of cobalt allows HSSE to retain its hot hardness longer than standard HSS and perform more reliably in stainless steel.
Workpiece materials
✓Structural and carbon steel
✓Gray cast iron
✓Aluminum and nonferrous alloys
▲Stainless steels — cobalt-alloyed HSSE handles them significantly better than HSS; coolant is still recommended
✗Hardened steels above 45 HRC
Guidelines for correct reaming
- Pre-drilled hole Ø7.8 mm — stock allowance of 0.2 mm on the diameter.
- Drill the initial hole perpendicular to the surface and with minimal runout — a finishing reamer follows the existing hole and will not correct its misalignment.
- Use coolant (emulsion or cutting oil); cast iron can be machined dry.
- Withdraw the tool without reversing its rotation — reverse rotation damages the cutting edges.
Frequently asked questions — Ø8 H7 reamer
Drill a hole Ø7.8 mm — stock allowance of approx. 0.2 mm on the diameter. Too little allowance causes the material to be compressed rather than cut; too much overloads the cutting edges and reduces hole accuracy.
In an ER collet or a precision chuck with minimal runout. Concentric clamping directly affects hole accuracy — excessive runout enlarges the hole beyond the tolerance zone.
The hole falls within the tolerance zone 8.000–8.015 mm, and surface roughness is approx. Ra 0.4–1.6 µm — this accuracy is sufficient for sliding fits and dowel pin holes.
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