The A2 designation for washers refers to the material grade—specifically Type 304 stainless steel, which is the most common and versatile stainless grade for general outdoor and domestic use.
Key Standards for A2 Washers
Like A4 washers, A2 washers are defined by international dimensional standards. The most common are:
- DIN 125 (ISO 7089): The primary standard for a plain flat washer.
- BS 4320: A British standard that categorizes washers into "Forms" based on thickness and diameter ratios.
Understanding "Forms" (BS 4320)
In the UK and Europe, A4 washers are often classified into "Forms" which determine their specific proportions:
|
Form
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Description
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Use Case
|
|
Form A
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Normal diameter, normal thickness
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General purpose engineering
|
|
Form B
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Normal diameter, light thickness
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Light-duty applications
|
|
Form C
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Large diameter, normal thickness
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Marine decks and cleats
|
|
Form G
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Largest diameter and extra thickness
|
Heavy-duty load spreading
|
A2 vs. A4: Which should you use?
While they often share the same dimensions, the material property is the differentiator:
|
Feature
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A2 (304 Stainless)
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A4 (316 Stainless)
|
|
Best For
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General outdoor use, DIY, kitchens
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Marine, coastal, and chemical environments
|
|
Resistance
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Good corrosion resistance
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Superior resistance (acid/salt)
|
|
Magnetic?
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Generally non-magnetic
|
Generally non-magnetic
|
|
Cost
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Typically more affordable
|
More expensive due to Molybdenum
|
