Are you allowed to substitute F436 hard washers when F844 cut washers are called out?

In general substituting one grade of fastener for another is a bad idea, as that substitution can open you up to liability concerns, but does this apply to washers? ASTM F844 covers standard, unhardened steel washers for general use. ASTM F436 covers hardened steel washers used with most high strength bolts and F1554 anchor bolts. F844 is pretty lenient in what it allows, in fact the only real restriction is that washers must be unhardened and made of steel. This means that strictly speaking, F436 washers shouldn’t be substituted for F844, even if the hardened washer has the same physical dimensions.

Why might someone want to substitute F436 washers for F844 washers?

The most common reason is domesticity requirements. Domestic F844 washers are not readily available, so to provide washers that meet the domestic requirements of some projects F436 washers are provided, as they are readily available (and something we stock).

Less common, but worth considering is the difference in size of the two washers. F844 washers are usually dimensioned per B18.21.1 (also known as USS pattern) whereas F436 washers are dimensioned per the F436 specification (the SAE pattern matches this). Certain applications may want a smaller washer and therefore prefer the F436 washer.

If you have any questions about washers, substituting fasteners or anything else, please give one of our helpful team members a call, and we will be happy to help.



    ASME B18.21.1 refers you to ASTM F844 for flatness and parallelism tolerances.
    But, nowhere on your site is this addressed… just ID/OD/TH. Did I miss something

    @Seadog- The standard summaries on our website are just that, and as such do not contain every detail. That said, you are correct that flatness is a requirement of F844. For washers 1/2″ and smaller, the out of flat maximum is 0.007″. For washers 9/16 thru 1-1/4, it is 0.010″ and washers larger than 1-1/4 it is 0.015″. I hope that helps.

    @Keyur- F844 washers do not have any specific chemical requirements, so they can be made from just about anything, mild steel included.

    @Jaseer- We are not familiar with grade 4.6 as it relates to washers, although we believe it to be a low strength material vs high strength for F436. You will need to pass any substitutions by the project engineer.

    @Mubashir- ASTM F844 does not have any specific chemical requirements, however most manufacturers choose to make them from low carbon steel.

    To continue this query, are stainless steel washers available in extra heavy thicknesses? What dimensional standards do stainless steel washers follow?

    @Angel- Heavy thickness stainless washers could easily be manufactured, but they are not available off the shelf. ASME B18.21.1 covers the dimensions for all standard washers, but there are several types within that standard and it seems that different manufacturers all choose different types, so it varies from supplier to supplier.

    Is there a common hardened stainless steel (316) flat washer available for use with ASTM A193 B8M, Class 2 bolts for ASME Pipe Flange bolting? How would it be specified (Possibly to ASTM 193)? Is there a significant cost increase over non hardened stainless steel washers?

    @Chuck- No, there is not. Stainless 316 flat washers are only available as commercial grade washers, hardened 316 washers are not available.

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