I'm trying to learn the standard nomenclature for the steel and stainless steel mainly used in the bolts, screws, nuts, and other fasteners in general. So far I have created this table:

|      Metric / Class     |   Imperial / Grade  |        Material        |
|      ISO 898-1 / 8.8    |     SAE J429 / 5    |          steel         |
|     ISO 898-1 / 10.9    |     SAE J429 / 8    |          Steel         |
|           12.9          |       ASTM A574     |          Steel         |
|            304          |          A2         |     Stainless steel    |
|            316          |          A4         |     Stainless steel    |

For example, metric system categories steels into classes according to the ISO 898-1 standard. While the Imperial system uses the SAE J429 standard to distinguish steels by grades. It seems like my table makes sense for steel, but for the stainless steels, I do not understand the grades/classes. For example, I'm not sure if 316 designates a metric class equivalent to the A4 imperial grade?

From time to time I also see notations such as A4-80 EPK. I understand that the 80 part determines the minimum tensile strength. But I have no clue what the EPK could stand for.

  • 2
    $\begingroup$ You are mixing apples and oranges ; there is little or no correlation between steel alloys and fasteners. Such as 316 is a general designation of a stainless alloy ,no connection with form such as bar, plate, pipe , fastener, etc. $\endgroup$ Commented Dec 8, 2020 at 15:43
  • $\begingroup$ @blacksmith37 thanks for the comment. True. I'm aware that those alloys are used in a variety of applications but I'm at the moment focused on the fasteners. $\endgroup$
    – Foad
    Commented Dec 8, 2020 at 15:51
  • 1
    $\begingroup$ And ASTM may have many alloys in a specification ,so you still need an alloy designation. Such as A 193 and 194, the standard fasteners in any industry with pipe flanges; Alloy can be anything from carbon steel to stainless. $\endgroup$ Commented Dec 8, 2020 at 20:42


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