Bright Steel / GR
Grinding
Grinding is applied for applications requiring the highest surface quality and tightest tolerances. Excellent dimensional accuracy and mirror-like surface finish is achieved in h7/h8 tolerance classes. Preferred for critical parts such as precision hydraulic cylinders, piston rods, and bearing shafts.
Technical Specifications
Key Features
- Tightest tolerance class (h7) - micron-level precision
- Excellent surface quality (Ra ≤ 0.4 µm)
- Mirror-like surface finish
- Straightness ≤ 0.5mm/m
- Ideal surface preparation for chrome plating
- Surface compatible with sealing elements
- Ovality and taper at minimum levels
- High precision dimensional repeatability
- Defect-free production for safety-critical parts
- Applicable on heat-treated or raw material
Applications
- Precision hydraulic cylinder pistons
- Pneumatic cylinder rods
- Chrome-plated piston rods
- Bearing shafts and axle pins
- Linear motion systems (linear shafts)
- Injection molding machine tie bars
- Printing machine shafts
- Medical equipment components
Dimension Table
| Profile | Size Range (mm) | Tolerance | Standard | Surface (Ra) |
|---|---|---|---|---|
| Round | 10 - 20 | h7 | EN 10278 | ≤ 0.4 µm |
| Round | 20 - 30 | h7 | EN 10278 | ≤ 0.4 µm |
| Round | 30 - 50 | h7/h8 | EN 10278 | ≤ 0.6 µm |
| Round | 50 - 65 | h8 | EN 10278 | ≤ 0.8 µm |
| Round | 65 - 80 | h8/h9 | EN 10278 | ≤ 0.8 µm |
Technical Notes
- 01h7 tolerance requires micron-level precision (e.g., Ø30mm: -0/+21µm).
- 02Material must be cold drawn or peeled prior to grinding.
- 03Centerless grinding is economical for high-volume production.
- 04Surface roughness must be Ra ≤ 0.4 µm before chrome plating.
- 05Standard length: 3000-6000mm, max 7000mm production possible.
- 06Machined surface is coated with protective oil against oxidation.
- 07Grinding process also improves straightness tolerance.
Steel Grades
Other Types
What is bright steel?
Bright steel is hot-rolled bar finished cold — by cold drawing, peeling/turning or grinding — to a precise size and clean surface. Typical tolerances: h9/h11 for cold drawn, h6–h9 for ground bar (ISO 286). With its scale-free bright surface, tight tolerance and straightness, it often needs no further machining (EN 10277).
Cold drawing vs peeling vs grinding
Cold drawing: the bar is pulled through a die; strain hardening raises yield strength by ~10–20% and gives h9/h11 tolerance — the most economical bright product. Peeling (turning): the surface layer is machined off, removing surface cracks and decarburization without adding residual stress — ideal for large diameters and Q&T grades. Grinding: the tightest tolerance (h6–h9) and the best finish (Ra ≤ 0.8 µm) — for shafts and pins. Typical grades: C45, 42CrMo4, 11SMn30, 16MnCr5.
Frequently Asked Questions
Bright steel vs hot rolled — what is the difference?+
Bright steel is cold finished: scale-free surface, h6–h11 tolerance and high straightness; hot rolled has scale and wide tolerances and is usually bought for further machining.
Does cold drawing increase strength?+
Yes; strain hardening typically raises yield strength by 10–20%, with slightly reduced ductility. Stress-relief annealing is applied where needed.
When is peeled (turned) bar preferred?+
For large diameters, quenched-and-tempered grades, and when surface defects/decarburization must be fully removed — it gives a clean surface without adding residual stress.
Which tolerances are standard for bright steel?+
h9 or h11 for cold drawn, h6–h9 for ground bar (ISO 286-2, EN 10277).
Related Blog Posts
Technical articles, guides and industry analyses
C45 vs 42CrMo4 Steel: Carbon or Alloy — Which to Choose?
We compare C45 (1045) carbon steel with 42CrMo4 (4140) chrome-moly quenched & tempered steel by hardenability, strength, welding and cost — which to choose and when?
Quenched and Tempered Steels: EN 10083 Grades, Values and How to Choose
Quenched and tempered (Q&T) steel is the class that delivers strength and toughness together. We put the six main EN 10083 grades — C45, 25CrMo4, 42CrMo4, 39NiCrMo3, 34CrNiMo6, 51CrV4 — into one table with chemistry, section-dependent values and selection criteria.