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Description
Diameter D Ø27 mm
Tolerance k1127.000–27.130 mm
Morse taper MT3
Material HSS
Bridge reamer 27 for metal and rivet holes — technical data
NRRa — bridge reamer, HSS DIN 311
| Technical Data | |
|---|---|
| Cutting diameter D (k11) | Ø27 mm (27.000–27.130 mm) |
| Morse taper | MT3 |
| Flute length l | 195 mm |
| Overall length L | 311 mm |
| Number of teeth Z | 5 |
| Type | NRRa — bridge reamer |
| Dimensional standard | DIN 311 |
| Material | HSS (high-speed steel) |
Manufacturing tolerance k11 for diameter 27 mm
| Class | Deviations [mm] | Dimension [mm] | |
|---|---|---|---|
| k11 | +0.130 / 0 | 27.000 – 27.130 | VERSION |
Bridge reamers are manufactured to tolerance k11 — holes for rivets and fitted bolts do not require H7 accuracy, and the positive size deviation makes it easier to fit the plate stack together.
Cutting data for the 27 bridge reamer
Indicative values Ø27 mm Z = 5
| Material group (ISO 513) | Vc [m/min] | fz [mm/tooth] | n [rpm] Ø27 | f [mm/min] Z=5 |
|---|---|---|---|---|
| PStructural and carbon steel | 8–10 | 0.20–0.28 | 94 | 94 |
| MStainless steel | 2–3 | 0.20–0.28 | 24 | 24 |
| KCast iron | 3–5 | 0.20–0.28 | 35 | 35 |
| NAluminum and light alloys | 12–16 | 0.24–0.32 | 141 | 169 |
Vc — cutting speed, fz — feed per tooth (catalog values for HSS, selected for a diameter of Ø27 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 = 5. Start with the lower values and adjust according to the material and clamping rigidity.
You may also need: Cutting parameters calculator
Applications of the 27 bridge reamer for metal and rivet holes
Holes for rivets and fitted bolts in steel structures
Bridge reamer 27 for metal and rivet holes — NRRa bridge reamer according to DIN 311 with Morse taper shank MT3 made of high-speed steel (HSS) HSS. Designed for reaming holes for rivets and fitted bolts in steel structures, bridges, and tanks. The long, slender cutting section allows holes in plate stacks to be reamed and misaligned assembly holes to be brought into alignment. The slight taper of the guiding section (approx. 1:10) brings misaligned holes onto a common axis, left-hand spiral flutes push chips toward the exit, and the steam-treated finish (uncoated) reduces chip adhesion.
The 27 bridge reamer for rivet holes works simultaneously in holes through several components being joined — it corrects hole misalignment, establishes a common axis, and sizes the hole for a rivet or fitted bolt. 5 cutting edges with a long cutting section guide the tool steadily through the plate stack. HSS retains its hardness and wear resistance even at elevated cutting temperatures.
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
- Pre-drilled hole Ø26.7 mm — stock allowance of 0.3 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 — 27 bridge reamer
The 27 bridge reamer is used to ream and size holes for rivets and fitted bolts in plates being joined. It is used in structural steelwork and bridges, as well as boiler and pressure vessel construction — wherever holes in a stack of plates must be brought to a common axis and size.
For machine reaming, predrill a hole Ø26.7 mm, leaving a stock allowance of 0.3 mm on the diameter — this allowance provides material for the reamer to remove to size while straightening the axis. During field assembly, a bridge reamer enlarges and aligns existing, misaligned rivet holes, including when used with a handheld pneumatic drill.
The 27 bridge reamer aligns misaligned holes in a plate stack and works to tolerance k11, while a standard machine reamer finishes a single, prealigned hole to a precise tolerance H7. The long, tapered cutting section guides the bridge reamer through several plates being joined with rivets and fitted bolts. This is why a bridge reamer is chosen for assembling riveted structures, while an H7 finishing reamer is used for precision fitted holes.
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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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