Tolerance Iso 2768 Mk Pdf [portable] -

The ISO 2768-1 and ISO 2768-2 standards define general geometrical tolerances for parts produced by machining or metal removal. The designation "mK" indicates a specific combination of tolerance classes for linear/angular dimensions and geometrical features. Understanding the "mK" Designation

m (Lower Case): Refers to ISO 2768-1, representing the "medium" tolerance class for linear and angular dimensions (e.g., lengths, radii, and diameters).

K (Upper Case): Refers to ISO 2768-2, representing the "K" tolerance class for general geometrical tolerances (e.g., flatness, straightness, and symmetry). ISO 2768-1: Linear & Angular Dimensions (Class "m")

This section covers dimensions without individual tolerance indications. All values in the table below are in millimeters (mm). Nominal Size Range (mm) 120 to 400 400 to 1000 1000 to 2000 Tolerance (m - medium) ±0.1plus or minus 0.1 ±0.1plus or minus 0.1 ±0.2plus or minus 0.2 ±0.3plus or minus 0.3 ±0.5plus or minus 0.5 ±0.8plus or minus 0.8 ±1.2plus or minus 1.2

External Radii and Chamfer Heights: For the "m" class, the tolerance is ±0.2plus or minus 0.2 mm for sizes 0.5–3 mm and ±0.5plus or minus 0.5 mm for sizes 3–6 mm.

Angular Dimensions: For the "m" class, the tolerance ranges from ±1∘plus or minus 1 raised to the composed with power (for lengths up to 10 mm) to (for lengths over 400 mm). ISO 2768-2: Geometrical Tolerances (Class "K")

This section applies to features like straightness, flatness, and perpendicularity. Nominal Length Range (mm) 100 to 300 300 to 1000 1000 to 3000 Straightness/Flatness Perpendicularity Symmetry

Run-out: The tolerance for circular run-out in class K is 0.2 mm. Why Use ISO 2768 mK? Tolerance Iso 2768 Mk Pdf

Simplification: It removes the need to specify tolerances for every single dimension on a drawing, keeping it clean and readable.

Standardization: It ensures that a machine shop understands the required level of precision based on standard workshop capabilities.

Cost Efficiency: Using "medium" tolerances (m) is generally cost-effective as it aligns with standard CNC machining capabilities without requiring expensive precision finishing. Practical Implementation

When using this standard, the drawing title block should explicitly state: ISO 2768-mK. This informs the manufacturer that any dimension without a specific tolerance must adhere to the "medium" and "K" class values listed above.

3. "The PDF is legally binding."

The free PDFs found online are reference copies. For a legal contract (e.g., aerospace or medical devices), you must purchase the official standard from ISO or your local national body (like ANSI or BSI).

Part 2: The "K" (Geometrical Tolerances)

The uppercase "K" refers to ISO 2768-2 (General tolerances for geometrical tolerances). This part covers characteristics like straightness, flatness, perpendicularity, and symmetry.

There are three classes for geometric tolerances: The ISO 2768-1 and ISO 2768-2 standards define

The "K" indicates a standard geometrical tolerance class often used for standard machining processes. It allows for slightly more deviation than class "H" but is tighter than class "L."

Part 1: The "m" (Linear and Angular Dimensions)

The lowercase "m" refers to ISO 2768-1 (General tolerances for linear and angular dimensions). This part covers lengths, widths, diameters, and angles.

There are four classes for linear tolerances:

The "m" indicates a medium tolerance class. This is the most common default for general machining. It balances precision with manufacturing efficiency. For example, under class "m", a dimension between 6mm and 30mm would have a general tolerance of ±0.2 mm.

3.2 Angular Dimensions – Permissible Deviations

| Nominal Length of Shorter Side | Tolerance (mm/m or °/') | |--------------------------------|--------------------------| | ≤ 100 mm | ±1° = ±60' | | >100 to 300 mm | ±0° 30' | | >300 to 1000 mm | ±0° 15' | | >1000 to 3000 mm | ±0° 10' |

Alternatively: ±0.5 mm per 100 mm length for general angle dimensions.

What is ISO 2768? The Basics

ISO 2768 is an international standard published by the International Organization for Standardization (ISO). It is titled: "General tolerances — Tolerances for linear and angular dimensions without individual tolerance indications." H K L

In simple terms: If a dimension on a drawing does not have a specific tolerance written next to it, the rules of ISO 2768 automatically apply.

The standard is divided into two parts:

  1. ISO 2768-1: Tolerances for linear and angular dimensions (lengths, radii, chamfers, angles).
  2. ISO 2768-2: Geometrical tolerances (flatness, straightness, perpendicularity, symmetry, runout).

3. "You don't need to inspect MK tolerances"

Wrong. You must inspect them. If a drawing says "General Tolerance ISO 2768-mK" and you produce a part with a 1mm warp on a 100mm face, you have failed the K class (max allowed is 0.2mm). The part is non-conforming.

Decoding the Code: What does "mK" mean?

The magic is in the suffix: m and K.

Decoding "MK" in ISO 2768

The keyword "ISO 2768 MK" refers to a specific combination of tolerance classes from the two parts of the standard.

Therefore, "ISO 2768 MK" means: