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This article provides a detailed exploration of GB/T 1804-2000, equivalent to ISO 2768-1:1989, focusing on tolerances for unspecified linear and angular dimensions. The structure includes:
- Introduction to the Standard
- Table 1: Linear Dimensions Tolerances
- Table 2: Chamfer and Fillet Radii Tolerances
- Table 3: Angular Dimensions Tolerances
- Indications on Drawings
- Usein kysytyt kysymykset (UKK)
Introduction to the Standard
GB/T 1804-2000 specifies general tolerances for linear and angular dimensions without individual indications, applicable to metal machined parts and adaptable for other materials. This standard categorizes tolerances into four grades: fine (f), medium (m), coarse (c), and very coarse (v), ensuring consistency in manufacturing where specific tolerances are omitted.
It covers linear dimensions, chamfer heights and fillet radii, and angular dimensions through three tables. Implementing this standard simplifies design processes, reduces drawing clutter, and maintains quality control in mechanical engineering applications such as machinery assembly and structural components.
- Fine (f) grade suits precision engineering requiring tight tolerances.
- Medium (m) grade is commonly used for general mechanical parts.
- Coarse (c) and very coarse (v) grades apply to less critical dimensions.
This guide offers practical insights for engineers to select appropriate grades, ensuring compliance and optimal performance in production.
Table 1: Linear Dimensions Tolerances
Table 1 provides limit deviations for linear dimensions in mm, segmented by basic size ranges. These values apply to features like external and internal dimensions, steps, and diameters without specified tolerances, aiding in uniform manufacturing precision.
| Tolerance Grade | Nominal Size Ranges (mm) | |||||||
|---|---|---|---|---|---|---|---|---|
| 0.5~3 | >3~6 | >6~30 | >30~120 | >120~400 | >400~1000 | >1000~2000 | >2000~4000 | |
| f (fine) | ±0.05 | ±0.05 | ±0.1 | ±0.15 | ±0.2 | ±0.3 | ±0.5 | – |
| m (medium) | ±0.1 | ±0.1 | ±0.2 | ±0.3 | ±0.5 | ±0.8 | ±1.2 | ±2 |
| c (coarse) | ±0.2 | ±0.3 | ±0.5 | ±0.8 | ±1.2 | ±2 | ±3 | ±4 |
| v (very coarse) | – | ±0.5 | ±1 | ±1.5 | ±2.5 | ±4 | ±6 | ±8 |
Select grades based on application precision; for example, use f for high-accuracy components to minimize assembly issues.
Table 2: Chamfer and Fillet Radii Tolerances
Table 2 outlines limit deviations for fillet radii and chamfer heights in mm, essential for edge treatments in parts to avoid stress concentrations and ensure safety.
| Tolerance Grade | Nominal Size Ranges (mm) | |||
|---|---|---|---|---|
| 0.5~3 | >3~6 | >6~30 | >30 | |
| f (fine) | ±0.2 | ±0.5 | ±1 | ±2 |
| m (medium) | ±0.2 | ±0.5 | ±1 | ±2 |
| c (coarse) | ±0.4 | ±1 | ±2 | ±4 |
| v (very coarse) | ±0.4 | ±1 | ±2 | ±4 |
f and m grades share values for consistency in precision work, while c and v allow larger deviations for robust designs.
Table 3: Angular Dimensions Tolerances
Table 3 details limit deviations for angular dimensions, determined by the shorter side length in mm. These are vital for ensuring proper fit in angled features like tapers.
| Tolerance Grade | Length of Shorter Side (mm) | ||||
|---|---|---|---|---|---|
| ≤10 | >10~50 | >50~120 | >120~400 | >400 | |
| f (fine) | ±1° | ±30′ | ±20′ | ±10′ | ±5′ |
| m (medium) | ±1° | ±30′ | ±20′ | ±10′ | ±5′ |
| c (coarse) | ±1°30′ | ±1° | ±30′ | ±15′ | ±10′ |
| v (very coarse) | ±3° | ±2° | ±1° | ±30′ | ±20′ |
Angular tolerances decrease with larger side lengths, reflecting reduced relative impact on overall geometry.
Indications on Drawings
To apply GB/T 1804-2000, note the standard and grade near the title block or in technical requirements. For medium grade, indicate “GB/T 1804-m”. This ensures clear communication of tolerance expectations.
- Excludes dimensions covered by other standards or in parentheses.
- Judgment: Parts failing functional requirements due to tolerances are rejected.
- Applies to metal cutting; reference for other processes.
Proper notation streamlines inspection and manufacturing, aligning with international practices like ISO 2768.
Usein kysytyt kysymykset (UKK)
- What is the scope of GB/T 1804-2000?
It covers unspecified linear and angular dimensions for machined metal parts, excluding those in other standards or parentheses. - How to choose a tolerance grade?
Select f for precision, m for general use, c or v for cost-effective, less critical applications based on functional needs. - Why combine f and m in Table 2?
They share identical deviations, simplifying application for chamfers and fillets in precision and medium scenarios. - How are angular tolerances determined?
By the shorter side length, with deviations in degrees and minutes decreasing as size increases for accuracy. - What if a dimension exceeds table ranges?
Refer to equivalent ISO 2768 or consult specific standards; extend patterns logically for larger sizes. - How to indicate on drawings?
Note “GB/T 1804-[grade]” in the title block to apply general tolerances uniformly.
