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Description
Diameter D Ø31.75 mm
Tolerance h831.711–31.750 mm
Morse taper MT3
Material HSS
Taper shank roughing reamer Ø31.75 for metal — technical data
NRTa — shank-type roughing reamer, Morse taper shank, HSS
| Technical Data | |
|---|---|
| Cutting diameter D (h8) | Ø31.75 mm (31.711–31.750 mm) |
| Morse taper | MT3 |
| Flute length l | 60 mm |
| Overall length L | 270 mm |
| Type | NRTa — shank-type roughing reamer, Morse taper shank |
| Material | HSS (high-speed steel) |
Manufacturing tolerance h8 for a diameter of 31.75 mm
| Class | Deviations [mm] | Dimension [mm] | |
|---|---|---|---|
| h8 | 0 / −0.039 | 31.711 – 31.750 | VERSION |
Cutting diameter 31.75 mm prepares the hole for a finishing reamer Ø32 H7 — the roughing reamer leaves an allowance of approx. 0.25 mm on the diameter for finish reaming.
Cutting data for the roughing reamer Ø31.75
Indicative values for Ø31.75 mm
| Material group (ISO 513) | Vc [m/min] | fz [mm/tooth] | n [rpm] Ø31.75 |
|---|---|---|---|
| PStructural and carbon steel | 8–10 | 0.20–0.28 | 80 |
| MStainless steel | 2–3 | 0.20–0.28 | 20 |
| KCast iron | 3–5 | 0.20–0.28 | 30 |
| NAluminum and light alloys | 12–16 | 0.24–0.32 | 120 |
Vc — cutting speed, fz — feed per tooth (catalog values for HSS, selected for a diameter of Ø31.75 mm). Spindle speeds were calculated for the lower end of the range: n = (Vc × 1000) ÷ (π × D). Start with the lower values and adjust according to the material and clamping rigidity.
You may also need: Cutting parameters calculator
Applications of the roughing reamer Ø31.75 for metal
Rough machining of holes before finish reaming
Taper shank roughing reamer Ø31.75 for metal Morse MT3 — NRTa shank-type roughing reamer made of high-speed steel (HSS) HSS. Used for preliminary reaming of drilled holes — it removes a larger allowance, corrects the hole axis, and prepares the hole for a finishing reamer. The tool face has a ~45° lead-in chamfer for centered entry, while the guide margins on the cutting edges keep the tool aligned with the hole axis.
The Ø31.75 roughing reamer for metal handles the most demanding work after drilling — it corrects form errors, aligns the hole axis, and leaves a controlled stock allowance for the finishing reamer. Diameter 31.75 mm corresponds to a finished hole of Ø32 H7 (allowance of approx. 0.25 mm on the diameter). Cutting edges with large flutes evacuate chips efficiently when removing larger stock allowances, while HSS withstands demanding cutting conditions. Larger diameters are used for bearing and bushing seats and holes in machine housings, where consistent dimensions along the entire length are essential.
Workpiece materials
✓Structural and carbon steel
✓Gray cast iron
✓Aluminum and nonferrous alloys
▲Stainless steels — reduced cutting speed, generous coolant supply
✗Hardened steels above 45 HRC
Guidelines for correct reaming
- After rough reaming, ream to final size with a finishing reamer Ø32 H7 — stock allowance of 0.25 mm on the diameter.
- 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 — roughing reamer Ø31.75
A roughing reamer removes a large allowance after drilling, straightens the axis, and improves hole shape, but does not provide H7 tolerance. The hole is brought to final size with a finishing reamer.
The 31.75 mm diameter is selected for a finished hole of Ø32 H7 — after rough reaming, an allowance of approx. 0.25 mm remains on the diameter for the finishing reamer.
The short NRTa is more rigid — better for standard holes when clamped close to the spindle. The long NRTb with spiral flutes reaches deeper and evacuates chips from deep holes more efficiently.
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| 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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