General Tolerances Reference Table
Linear, angular, and geometrical tolerances for dimensions without individual tolerance indications. Four accuracy classes: fine (f), medium (m), coarse (c), very coarse (v).
Accuracy Classes
Smallest dimension range. Fine class ±0.05mm for precision parts. Medium ±0.1mm is the default for most drawings. Coarse ±0.2mm for non-critical features.
Small dimensions. Fine and medium remain the same as 0.5-3mm. Coarse increases to ±0.3mm. Very coarse ±0.8mm for rough castings.
Common range for most machined parts. Medium ±0.2mm is standard for general engineering. Fine ±0.1mm for precision fits.
Medium size range. Medium ±0.3mm covers most general machinery. Fine ±0.15mm for precision components. Coarse ±0.8mm for structural parts.
Large dimensions. Medium ±0.5mm standard for large machined parts. Coarse ±1.2mm for structural and welded fabrications.
Very large dimensions. Medium ±0.8mm for large fabrications. Coarse ±2.0mm for structural steel. Very coarse ±4.0mm for large castings.
Extra large dimensions. Fine ±0.5mm rarely used at this scale. Medium ±1.2mm for large precision fabrications. Coarse ±3.0mm for structural.
Largest range covered by ISO 2768. Fine class not defined. Medium ±2.0mm for large welded structures. Very coarse ±8.0mm for very large castings.
Small angles up to 10°. Fine and medium both ±1°. Coarse ±1°30′. Very coarse ±3° for rough angular features.
Medium angles. Fine and medium ±0°30′. Coarse ±1°. Very coarse ±2°. Applied to angles on drawings without individual tolerance.
Large angles. Fine and medium ±0°20′. Coarse ±0°30′. Very coarse ±1°. Common for chamfers and bevels.
Very large angles (reflex). Fine and medium ±0°10′. Coarse ±0°15′. Very coarse ±0°30′. Rare in practice.
Angular tolerance depends on the shorter side length of the angle. For short sides ≤10mm, tolerances are wider due to measurement difficulty.
For angle sides 10-50mm. Medium ±0°30′ is standard for chamfers and bevels on typical machined parts.
For angle sides 50-120mm. Medium ±0°20′ for general engineering. Fine ±0°20′ same as medium.
For angle sides 120-400mm. Tolerances tighten with longer sides because angular error translates to larger linear deviation.
Flatness tolerance for surfaces up to 100mm. Values in mm. Fine 0.02mm for precision ground surfaces. Medium 0.05mm for general machined faces.
Flatness for 100-300mm surfaces. Medium 0.1mm standard for machined mounting surfaces. Coarse 0.2mm for non-critical faces.
Flatness for 300-1000mm surfaces. Medium 0.2mm for large machine bases. Coarse 0.4mm for structural mounting surfaces.
Straightness for edges/lines up to 100mm. Same values as flatness. Fine 0.02mm for precision guides. Medium 0.05mm for general edges.
Straightness for 100-300mm. Medium 0.1mm for general machined edges. Coarse 0.2mm for non-critical features.
Perpendicularity for features up to 100mm. Medium 0.1mm for general machined corners. Fine 0.05mm for precision square features.
Perpendicularity for 100-300mm. Medium 0.2mm for standard machined brackets. Coarse 0.4mm for structural brackets.
Symmetry tolerance for features up to 100mm. Medium 0.1mm for general symmetric features. Fine 0.05mm for precision.
Circular runout for diameters up to 100mm. Fine 0.02mm for precision shafts. Medium 0.05mm for general rotating parts.
Circular runout for 100-300mm diameters. Medium 0.1mm for general shafts and journals. Coarse 0.2mm for non-critical rotations.
General tolerance class indicated in title block or near drawing. Format: ISO 2768-mK where m = linear/angular class (f/m/c/v) and K = geometrical class (A/B/C/D). Example: ISO 2768-mK means medium linear + class K geometrical.
ISO 2768-2 geometrical class A corresponds to fine tolerances. Used for precision instruments and measuring equipment. Equivalent to f class for linear.
ISO 2768-2 geometrical class B corresponds to medium tolerances. Default for general engineering. Equivalent to m class for linear.
ISO 2768-2 geometrical class C corresponds to coarse tolerances. Used for structural and non-critical parts. Equivalent to c class for linear.
ISO 2768-2 geometrical class D corresponds to very coarse tolerances. Used for castings, forgings, and rough fabrications. Equivalent to v class for linear.
General tolerances apply ONLY when no individual tolerance is indicated. If a dimension has its own tolerance (e.g. 50±0.01), the individual tolerance takes precedence. General tolerances cover the rest.
ISO 2768 superseded DIN 7168. The old German standard used the same f/m/c/g classes (g = very coarse, now v in ISO). Many European drawings still reference DIN 7168 — values are identical.
ISO 2768 General Tolerances Advanced Efficiency Guide
ISO 2768 General Tolerances Efficiency Optimization & Best Practices
Medium (m) is the default — don't over-specify
ISO 2768-m is the most common general tolerance class. It covers the vast majority of machined parts. Only use fine (f) when precision is truly required — it increases cost significantly. Coarse (c) is appropriate for structural and non-critical features. Always indicate the class in the drawing title block.
General tolerances reduce drawing clutter
The purpose of ISO 2768 is to avoid specifying tolerances on every dimension. Only dimensions that need tighter or different tolerances get individual indications. All other dimensions are covered by the general tolerance class in the title block. This makes drawings cleaner and easier to read. Example: title block says "ISO 2768-mK", a dimension marked 50 is ±0.3mm, but 50±0.01 overrides to the tighter tolerance.
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Engineering Methodology & Design Standards: General Tolerances Reference Table
Discipline: CNC Machining, Sheet Metal Fabrication & Dimensional Metrology
Governing Mathematical Formulation
In professional CNC Machining, Sheet Metal Fabrication & Dimensional Metrology workflows, accurate sizing and performance verification require consistent unit normalization and adherence to closed-form analytical mechanics. This General Tolerances Reference Table utility implements the standardized engineering formulation:
Standardized parametric evaluation for General Tolerances Reference TableISO 2768-1/2 general tolerances for linear dimensions, angular dimensions, and geometrical tolerances (fine, medium, coarse, very coarse). Every input change triggers an instant client-side recalculation across all coupled dependent variables, enabling rapid sensitivity analysis during preliminary and detailed CAD design phases.
Applicable Codes, Standards & CAD Integration
Synchronize sheet metal K-factors, tool radius compensation registers (G41/G42), and GD&T datum reference frames between your 3D CAD master model, CAM post-processor, and CMM inspection plan.
Engineering Verification Note: Analytical models assume homogeneous material behavior, steady-state boundary loading, and consistent dimensional units. Always apply appropriate service factors, corrosion allowances, or load and resistance factor design (LRFD / ASD) safety margins required by your governing code.
Frequently Asked Engineering Questions
Technical reference & verification guidelines for General Tolerances Reference Table
What governing equation and methodology does the General Tolerances Reference Table use?
The General Tolerances Reference Table evaluates iso 2768-1/2 general tolerances for linear dimensions, angular dimensions, and geometrical tolerances (fine, medium, coarse, very coarse) within the CNC Machining, Sheet Metal Fabrication & Dimensional Metrology domain using the governing formulation: Standardized parametric evaluation for General Tolerances Reference Table. All intermediate quantities are computed in double-precision floating-point arithmetic to prevent cumulative rounding drift before final design verification.
Which international engineering standards apply to General Tolerances Reference Table calculations?
Calculations and boundary assumptions in this utility align with recognized industry references including ISO 286-1 / ASME B4.1 (Limits and Fits), ASME Y14.5-2018 / ISO 1101 (GD&T), DIN 6935 (Sheet Metal Cold Bending), ISO 2768 (General Tolerances). When preparing formal calculation packages or P.E. stamp submittals, always verify local jurisdictional code amendments and project-specific safety factors.
How should I integrate results from the General Tolerances Reference Table into my CAD or BIM workflow?
Synchronize sheet metal K-factors, tool radius compensation registers (G41/G42), and GD&T datum reference frames between your 3D CAD master model, CAM post-processor, and CMM inspection plan. Using the baseline benchmark (standard nominal boundary parameters for General Tolerances Reference Table), the solver yields verified design compliance metrics for General Tolerances Reference Table, which can be directly cross-referenced against your parametric 3D assembly constraints, 2D fabrication drawings, or bill of materials (BOM).