Precision Parts ISO 2768 Tolerance Standard
Precision parts are a common type of parts in the manufacturing process, precision technology is usually processing high precision dimensions and complex shapes parts. in the manufacturing industry, precision parts are usually produced by specialized advanced CNC machines, ensuring parts’ dimensions, shape and quality meet strict requirements. the word “precision” has important meanings in the engineering and manufacturing industries, covering the following aspects.
High precision: precision means that the parts’ dimensions are highly precise and accurate. during the manufacturing process, precision parts need to be processed according to precise specifications and standards to ensure parts meet the design requirements. this high degree precision dimension usually requires advanced CNC machines and techniques to achieve.
Precision and stability: the precision parts manufacturing process needs to ensure the product’s precision and stability, it mean that during mass production, each part needs to maintain a consistent high quality to meet customer demands.
Complexity: precision parts usually have complex shapes and structures, this requires sophisticated manufacturing processes and technologies to accomplish. manufacturing these complex parts requires highly specialized knowledge and skills, MK is a precision parts manufacturer with 27 years of experience.
Material selection: material selection for precision parts is also critical. typically, these parts require the use of high-strength and wear-resistant materials to maintain parts stable performance during use.
In daily engineering drawings, many customers use ISO 2768-m or ISO2768-mK, so what is the ISO2768 standard?
ISO2768 is divided into two parts, namely ISO2768-1 and ISO2768-2
ISO2768-1 specifies precision parts’ unmarked tolerances for linear and angular dimensions. It is divided into 4 levels: precision grade (f), medium level (m), roughness level (c), and coarsest grade (v).
ISO 2768-2 specifies precision parts’ geometric shapes and unmarked tolerances, with three levels: H, K, and L.
It can be simply understood that ISO2768-1 is for dimension standard, and ISO2768-2 is for shape standard.
As mentioned before ISO2768-mK lowercase letter m represents the parts’ dimensions, angles, arcs, and bevels.
ISO2678-1 m grade, the capital letter K represents the parts’ geometric parameters, such as straightness, verticality, symmetry, and circularity.
precision parts ISO2768 -1 tolerance grades
In the precision parts manufacturing process, the tolerance grade is crucial for the part’s accuracy and quality control. here are four common tolerance levels: fine (f), medium (m), coarse (c), and coarsest (v), and tolerance grade detail explanations.
Precision grade (f):
Explanation: Precision grades indicate the tolerance range is very small, manufacturing process requires high degree accuracy dimension to ensure the part is exactly as designed.
Features: The tolerance range is very strict, requiring the part dimension, shape, and surface quality very precise.
Applicable scenarios: Usually suitable for extremely high precision parts requests, such as precision instrument parts, precision mechanical parts, etc.
Medium level (m):
Explanation: the medium grade tolerance range is relatively small, and also requires higher manufacturing accuracy, but it is looser than the f precision grade.
Features: the tolerance range is moderate, requiring precision parts dimensions and shape to remain stable within a certain range.
Applicable scenarios: suitable for general mechanical parts, precision automotive parts, precision electronic parts, and other daily tool application areas.
Roughness level (c):
Explanation: rough grades indicate a relatively wide tolerance range and less stringent requirements for part dimension and shape.
Features: The tolerance range is wide, and suitable for parts don’t need particularly strict dimensional requirements.
Applicable scenarios: usually suitable for parts with simpler structures and lower dimension requirements.
Coarsest grade (v):
Explanation: the coarsest grade means that the part has the largest tolerance range, and largest allowable dimensional deviation.
Features: the tolerance range is the loosest, suitable for dimensions and the shape is very loose parts.
Applicable scenarios: Suitable for some parts with simple structure and low functional requirements.
| ISO2768-1 tolerance standard – length limit dimensions | ||||
| nominal dimension | tolerance dimensions | |||
| range | f (fine) | m (medium ) | c (roughness ) | v (coarsest) |
| mm | tolerance mm | tolerance mm | tolerance mm | tolerance mm |
| 0.5-3 | ± 0.05 | ± 0.10 | ± 0.15 | – |
| 3- 6 | ± 0.05 | ± 0.10 | ± 0.20 | ± 0.50 |
| 6- 30 | ± 0.10 | ± 0.20 | ± 0.50 | ± 1.00 |
| 30- 120 | ± 0.15 | ± 0.30 | ± 0.80 | ± 1.50 |
| 120- 400 | ± 0.20 | ± 0.50 | ± 1.20 | ± 2.50 |
| 400- 1000 | ± 0.30 | ± 0.80 | ± 2.00 | ± 4.00 |
| 1000- 2000 | ± 0.50 | ± 1.20 | ± 3.00 | ± 6.00 |
| 2000- 4000 | – | ± 2.00 | ± 4.00 | ± 8.00 |
| ISO2768-1 tolerance standard – angle limit dimensions | ||||
| nominal dimension | tolerance dimensions | |||
| range | f (fine) | m (medium ) | c (roughness ) | v (coarsest) |
| mm | tolerance mm | tolerance mm | tolerance mm | tolerance mm |
| <10 | ± 10′ | ±1°30′ | ± 3° | |
| 10- 50 | ± 30′ | ± 1° | ± 2° | |
| 50- 120 | ± 20′ | ± 30′ | ± 1° | |
| 120- 400 | ± 10′ | ± 15′ | ± 30′ | |
| 400+ | ± 5′ | ± 10′ | ± 20′ | |
| ISO2768-1 bend radius (curvature) and bevel height (bevel angle) limit dimensions | ||||
| nominal dimension | tolerance dimensions | |||
| range | f (fine) | m (medium ) | c (roughness ) | v (coarsest) |
| mm | tolerance mm | tolerance mm | tolerance mm | tolerance mm |
| 0.5-3 | ± 0.20 | ± 0.40 | ||
| >3-6 | ± 0.50 | ± 1.00 | ||
| >6 | ± 1.00 | ± 2.00 | ||
precision parts ISO2768 -2 tolerance grades
In the ISO 2768 standard second part, ISO 2768-2 tolerance grades H, K, and L represent different tolerance grades for precision parts shapes. these tolerance grades provide different tolerance requirements, ranging from tight to loose.
below is the ISO 2768-2 tolerance detail, H, K, and L tolerance grade
H grade tolerance: H grade tolerance is a stricter tolerance grade in ISO 2768-2. tolerance grade H is suitable for higher precision parts required, control the parts’ stricter shape dimensional and smaller tolerance range are required.
K tolerance: K tolerance is the medium tolerance grade in ISO 2768-2.
tolerance grade K applies to precision automotive parts. The requirements are looser than those of grade H, but still stricter than grade L.
L tolerance: L tolerance is the loose tolerance grade in ISO 2768-2.
tolerance grade L is suitable for parts with less stringent dimensional requirements, and allowable dimensional relatively large deviation range.
| ISO2768-2 flatness and straightness general tolerances | ||||||
| numerical unit: mm | ||||||
| tolerance grade | ≦10 | >10~≦30 | >30~≦100 | >100~≦300 | >300~≦1000 | >1000~≦3000 |
| H | 0.02 | 0.05 | 0.1 | 0.2 | 0.3 | 0.4 |
| K | 0.05 | 0.1 | 0.2 | 0.4 | 0.6 | 0.8 |
| L | 0.1 | 0.2 | 0.4 | 0.8 | 1.2 | 1.6 |
| ISO2768-2 right angles general tolerances | ||||
| numerical unit: mm | ||||
| tolerance grade | ≦100 | >100~≦300 | >300~≦1000 | >1000~≦3000 |
| H | 0.2 | 0.3 | 0.4 | 0.5 |
| K | 0.4 | 0.6 | 0.8 | 1 |
| L | 0.6 | 1 | 1.5 | 2 |
| ISO2768-2 symmetry general tolerance | ||||
| numerical unit: mm | ||||
| tolerance grade | ≦100 | >100~≦300 | >300~≦1000 | >1000~≦3000 |
| H | 0.5 | |||
| K | 0.6 | 0.8 | 1 | |
| L | 0.6 | 1 | 1.5 | 2 |
| ISO2768-2 circular runout general tolerance | |
| numerical unit: mm | |
| tolerance grade | Swing grade |
| G | 0.1 |
| K | 0.2 |
| L | 0.5 |
MK precision parts manufacturer selects different tolerance grades according to customer requirements when designing and producing precision parts, ensuring parts dimensions are within a reasonable range. MK selects appropriate tolerance grades to control the part’s dimensional tolerance according to specific manufacturing needs, part functional requirements, and expected use environment. ensure the parts meet the design, quality, and performance requirements.
MK is a precision parts manufacturer with professional production machines and technical engineers. Our engineers have more than 10 years of experience in precision parts, and they graduated from electrical automation majors. we focus on producing high-precision, high-quality parts.
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