Understand F-grade and E-grade dimensional limits for drop and vertical press steel forgings per EN 10243-1 — and calculate exact tolerances for your part.
Closed-die and open-die steel forgings are shaped under high compressive forces in heated dies. Unlike CNC machining, final dimensions depend on billet size, die geometry, material shrinkage, flash trimming, and die wear. Standards such as EN 10243-1 (and the legacy German standard DIN 7526) define normal dimensional tolerances so engineers and buyers can specify realistic limits before quoting or machining stock allowance.
To determine applicable tolerances, you need the forging's largest nominal dimension, mass, steel material group, shape complexity category, forging method (vertical or horizontal press), and whether F-grade (normal) or E-grade (close) limits apply. Our Steel Forging Tolerance Calculator automates this lookup using EN 10243-1 table data.
General-purpose tolerances for typical drop and vertical press forgings. Use F-grade when standard dimensional variation is acceptable and cost-effective production is the priority. Applies to length, width, height, thickness, and permissible deflection or distortion limits.
Tighter tolerances for precision forgings that must meet stricter dimensional control before finish machining. E-grade values are always narrower than F-grade for the same nominal size. Specify E-grade only where functionally required—it increases process control and cost.
Both grades are defined in EN 10243-1 Part 1 for drop and vertical press steel die forgings. Permissible deflection and distortion are expressed as symmetric ± limits based on nominal size bands (see table below).
High-carbon and high-alloy steels are more difficult to deform and cause greater die wear than low-alloy grades. EN 10243-1 assigns material groups that shift tolerance table rows:
| Group | Carbon | Alloying Elements | Typical Grades |
|---|---|---|---|
| M1 | ≤ 0.65% | Mn, Ni, Cr, Mo, V, W combined ≤ 5% by mass | Most carbon and low-alloy steels (e.g. C45, 42CrMo4) |
| M2 | > 0.65% | Mn, Ni, Cr, Mo, V, W combined > 5% by mass | High-carbon tool steels, high-alloy grades |
Use the maximum permitted values from the steel specification to determine the group. M2 combinations with higher shape complexity (S3, S4) apply the largest table offsets.
Thin sections, pockets, and branched geometries shrink unevenly and require higher forming forces, producing larger dimensional variation. The shape complexity factor accounts for this:
mf = mass of the finished forging; mes = mass of the enveloping rectangular shape (length × width × height). The resulting ratio falls into one of four categories:
| Category | S Factor Range | Interpretation |
|---|---|---|
| S1 | 0.63 – 1.00 | Compact, simple shapes; lowest tolerance offset |
| S2 | 0.32 – 0.63 | Moderate branching or thinner sections |
| S3 | 0.16 – 0.32 | Thin webs, pockets, or multiple branches |
| S4 | 0 – 0.16 | Highly branched or very thin sections; largest offset |
In practice: divide the final part weight by the weight of the smallest box that fully contains the part. A solid cylindrical disk scores near S1; a thin-walled bracket with large cutouts may fall in S3 or S4.
Tolerance tables are indexed by two physical parameters:
Example: a 100 mm nominal diameter flange weighing 5 kg in M1/S1 carbon steel on a vertical press uses the calculator prefill /dzgc?size=100&weight=5&unit=Metric&difficulty=m1&complexity=s1.
EN 10243-1 specifies symmetric ± limits for permissible deflection and distortion as a function of nominal size. Representative F-grade and E-grade values from our lookup data:
| Nominal Size | F-Grade (±) | E-Grade (±) |
|---|---|---|
| ≤ 100 mm | ±0.6 mm | ±0.4 mm |
| 100 – 250 mm | ±0.7 – 1.0 mm | ±0.5 – 0.6 mm |
| 250 – 630 mm | ±1.1 – 1.6 mm | ±0.7 – 1.0 mm |
| 630 – 1250 mm | ±1.8 – 2.2 mm | ±1.1 – 1.4 mm |
| 1250 – 2500 mm | ±2.5 – 3.2 mm | ±1.6 – 2.0 mm |
Length, width, height, and thickness dimensional tolerances are separate table lookups that also depend on material group and shape complexity. Use the calculator for complete values.
The most common closed-die process. EN 10243-1 Part 1 covers drop and vertical press forgings. Tolerance output includes length/width/height (F and E), thickness (F and E), and deflection/distortion (F and E). This matches the default mode in our calculator.
Used for long axisymmetric parts (shafts, bars) forged horizontally. The calculator returns F-grade length/width/height and thickness tolerances plus F-grade deflection limits. E-grade thickness and deflection tables differ from vertical press applications.
Beyond dimensional tolerances, forged surfaces typically require Ra values between 3.2 and 12.5 μm for as-forged condition. Sealing or bearing surfaces may require 0.8 – 3.2 μm after machining. Critical defects such as cracks and folds are not permitted; minor pits or pockmarks may be acceptable if depth does not exceed 50% of the machining allowance.
For critical bores, faces, or keyways, specify additional machining stock rather than relying on forging tolerance alone. See also our Forging manufacturing method guide and manufacturing tolerances library.
Enter nominal size, weight, material group, shape complexity, and forging direction to get F-grade and E-grade dimensional limits instantly.
Steel Forging Tolerance CalculatorF-grade (normal) tolerances apply to typical drop and vertical press forgings where standard dimensional variation is acceptable. E-grade (close) tolerances are tighter and used when the forging must meet more precise dimensional requirements—often before minimal machining. E-grade limits are always narrower than F-grade for the same nominal size.
EN 10243-1 (Steel die forgings — Tolerances on dimensions — Part 1: Drop and vertical press forgings) is the primary European standard. It superseded DIN 7526 in many applications. Both define normal (F) and close (E) tolerance grades, material groups, and shape complexity factors used in tolerance lookup tables.
Shape complexity S = mf / mes, where mf is the mass of the finished forging and mes is the mass of the enveloping shape (length × width × height × steel density ≈ 0.00785 g/mm³). A ratio near 1.0 means a compact part (S1); thin or branched parts yield lower ratios (S3 or S4) and wider dimensional tolerances.
Use M2 when the steel specification has carbon content above 0.65% or when the combined specified content of Mn, Ni, Cr, Mo, V, and W exceeds 5% by mass. High-carbon and high-alloy steels are harder to deform and cause greater die wear, so tolerance tables apply a larger offset for M2 combinations.
Dimensional lookup tables differ by forging direction. Vertical press (drop) forgings typically have separate tolerance values for length/width/height, thickness, and permissible deflection for both F and E grades. Horizontal press forgings use a reduced set of dimension types—length/width/height and thickness—with F-grade deflection limits only in our calculator.
Tables are indexed by the largest nominal dimension of the forging and its mass. Larger dimensions and heavier parts generally fall into coarser tolerance bands because shrinkage, die wear, and thermal distortion scale with size. Enter both values when using the tolerance calculator for accurate results.
Tolerance methodology follows EN 10243-1: Steel die forgings — Tolerances on dimensions — Part 1: Drop and vertical press forgings (also published as BS EN 10243-1). Historical German practice used DIN 7526 for similar normal tolerance grades. Calculator logic and educational content align with industry tolerance lookup practices for non-circular steel die forgings.