In mechanical drawing chamfer (chamfer dimensioning), the meaning and standard usage of C2 and C are as follows:
1. Core Meaning
C2 indicates a 2 mm x 45° chamfer.
C is the abbreviation for the English word Chamfer.
2 represents the leg length (the axial and radial distance measured from the edge) as 2 mm.
45° is the default angle and is usually omitted.
When used alone, C does not conform to standards because it does not specify the actual size of the chamfer. Standard chamfer callouts must include a numerical value, such as C0.5, C1, C2, etc.
2. How to Read and Examples
Callout: C2
Read as: “C two” or “2 millimeter by 45 degree chamfer”
Meaning: Remove 2 mm of material in both perpendicular directions along the edge of the part, creating a 45° angle.
Other examples: C1 (1×45°), C0.5 (0.5×45°).
3. Common Questions
Why is only one number indicated?
Because the two legs of a 45° chamfer are equal in length, so a single number defines the geometry.
What if the angle is not 45°?
For non-45° chamfers, the “C” notation cannot be used. You must specify both the angle and the leg length, for example: 2mm x 30°.
Summary
C2: ✅ Standard, compliant chamfer callout, representing 2 x 45°.
C: ❌ Non-standard callout, as it lacks the numerical information needed to determine the chamfer size.
Next time you see a number after a C, such as C1.5, you’ll know it indicates a 1.5 mm x 45° chamfer.
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