Category: Reamers
How to Choose Reamers for H7 Tolerance
Achieving H7 hole tolerance (±0.012mm typical) consistently requires the right reamer choice and process discipline. Hooguu stocks reamers from Walter, OSG, YG-1, Sandvik, and Kennametal.
Reamer Material Selection
- HSS-Co — Cobalt-alloyed HSS, good for steel up to 30 HRC. Lowest cost.
- HSS-PM — Powder metallurgy HSS, finer grain, longer life than HSS-Co.
- Solid carbide — Best surface finish (Ra <0.4 µm achievable), 5-10× HSS life. Premium choice for production.
- Carbide-tipped (brazed) — Lower cost than solid carbide but less rigid; good for medium production.
Flute Geometry
- Straight flute — Through holes with continuous chip flow. Best for cast iron and short chips.
- Left-hand spiral flute — Through holes, chips ejected DOWN through the hole.
- Right-hand spiral flute — Blind holes, chips pulled UP and out.
Pre-Reaming Hole Size (Critical)
Wrong stock allowance is the #1 reason reamers fail to hit tolerance:
- HSS reamer: pre-drill = reamer dia − 0.4mm (for 6-25mm diameters)
- Carbide reamer: pre-drill = reamer dia − 0.2mm
- The pre-drilled hole MUST be round and straight — drill with through-coolant carbide drill, not jobber HSS
Speed and Feed (Reamers Need LOW speed, HIGH feed)
| Material | Carbide Vc (m/min) | Feed/rev (mm) |
|---|---|---|
| Mild steel | 40-60 | 0.40-0.60 |
| Stainless 304 | 15-25 | 0.30-0.45 |
| Cast iron | 30-50 | 0.50-0.80 |
| Aluminum | 80-120 | 0.50-0.90 |
| Hardened steel (45+ HRC) | 10-20 | 0.20-0.30 |
Coolant Strategy
Through-coolant reamers + 7+ bar flood pressure for H7 tolerance. Sulfur-based cutting oil for steel reaming gives better finish than water-soluble emulsion. Mist coolant only for aluminum.
Quality Control
Measure hole size with a plug gauge or air gauge — calipers give misleading readings on small holes. Check 3 axial positions (top, middle, bottom) for taper. Reamers wear at the entrance first; replace when entrance diameter drops 0.005mm below spec.
Browse our reamer catalog. See our complete H7-tolerance reamer guide.
How to Choose Reamers for H7 Tolerance
Achieving H7 hole tolerance (±0.012mm typical) consistently requires the right reamer choice and process discipline. Hooguu stocks reamers from Walter, OSG, YG-1, Sandvik, and Kennametal.
Reamer Material Selection
- HSS-Co — Cobalt-alloyed HSS, good for steel up to 30 HRC. Lowest cost.
- HSS-PM — Powder metallurgy HSS, finer grain, longer life than HSS-Co.
- Solid carbide — Best surface finish (Ra <0.4 µm achievable), 5-10× HSS life. Premium choice for production.
- Carbide-tipped (brazed) — Lower cost than solid carbide but less rigid; good for medium production.
Flute Geometry
- Straight flute — Through holes with continuous chip flow. Best for cast iron and short chips.
- Left-hand spiral flute — Through holes, chips ejected DOWN through the hole.
- Right-hand spiral flute — Blind holes, chips pulled UP and out.
Pre-Reaming Hole Size (Critical)
Wrong stock allowance is the #1 reason reamers fail to hit tolerance:
- HSS reamer: pre-drill = reamer dia − 0.4mm (for 6-25mm diameters)
- Carbide reamer: pre-drill = reamer dia − 0.2mm
- The pre-drilled hole MUST be round and straight — drill with through-coolant carbide drill, not jobber HSS
Speed and Feed (Reamers Need LOW speed, HIGH feed)
| Material | Carbide Vc (m/min) | Feed/rev (mm) |
|---|---|---|
| Mild steel | 40-60 | 0.40-0.60 |
| Stainless 304 | 15-25 | 0.30-0.45 |
| Cast iron | 30-50 | 0.50-0.80 |
| Aluminum | 80-120 | 0.50-0.90 |
| Hardened steel (45+ HRC) | 10-20 | 0.20-0.30 |
Coolant Strategy
Through-coolant reamers + 7+ bar flood pressure for H7 tolerance. Sulfur-based cutting oil for steel reaming gives better finish than water-soluble emulsion. Mist coolant only for aluminum.
Quality Control
Measure hole size with a plug gauge or air gauge — calipers give misleading readings on small holes. Check 3 axial positions (top, middle, bottom) for taper. Reamers wear at the entrance first; replace when entrance diameter drops 0.005mm below spec.
Browse our reamer catalog. See our complete H7-tolerance reamer guide.
