Can an A194 grade 2H nut be substituted for an A563 grade DH nut? If so, does it work the other way around... Can an A563 grade DH nut be substituted for an A194 grade 2H nut?

Both ASTM A194 Grade 2H nuts and ASTM A563 grade DH nuts are high strength nuts that undergo a heat treating process required to develop their strength characteristics. However, they are not necessarily interchangeable.

An A194 Grade 2H nut can always be substituted for an A563 Grade DH nut. In fact, the ASTM A563 nut specification specifically states that substituting an A194 Grade 2H is acceptable.

ASTM A563 – Table 3 – Note D states:

“Nuts made in accordance with the requirements of Specification A194/A194M, Grade 2H, and marked with its grade symbol are an acceptable equivalent for Grade DH nuts. When A194 zinc-coated inch series nuts are supplied, the zinc coating, overtapping, lubrication and rotational capacity testing shall be in accordance with Specification A563.”

Due to availability and/or cost issues, ASTM A194 Grade 2H nuts may be preferable to an ASTM A563 Grade DH nut. It is not uncommon for A563 Grade DH nuts to be completely unavailable in some diameters and finishes. The reverse is also true for A194 Grade 2H nuts, which can be unavailable or impractical from a cost perspective in certain diameters and finishes. Does this mean a supplier should substitute A563 Grade DH nuts for A194 Grade 2H nuts?

The answer is no. An ASTM A563 grade DH nut may be substituted for an ASTM A194 grade 2H nut under most, but not all, circumstances. A194 Grade 2H nuts undergo additional heat treating and testing processes that A563 Grade DH are not subjected to. This additional processing and testing allows A194 Grade 2H nuts to be used in high temperature applications. In particular, ASTM A193 Grade B7 (a high temperature bolt specification) specifically requires the use of A194 nuts. Though both grades of nut are identical in terms of strength, A563 Grade DH nuts are not an acceptable substitution for this bolt specification.

Both ASTM A563 Grade DH nuts and ASTM A194 Grade 2H nuts are compatible with the following ASTM bolt specifications:

The compatibility of nuts for various grades of bolts can be verified with our Nut Compatibility Chart.

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    Can anyone advise me what nut specification is suitable for an ASTM A574 bolt? noting that we are torqueing to near maximum pre-load of the bolt and hence Grade 8 are insufficient.

    @Nathaniel- A574 sockets are typically used in tapped holes (without nuts) and so therefore the A574 standard does not recommend any specific nut. SAE J995 grade 8 nuts are proof loaded at 150ksi. If those are not sufficient, you may go to an A194 grade 2H nut which is proof loaded at 175ksi and also comes in a heavy hex pattern. Beyond that, we are not aware of anything stronger – you would have to have something custom made.

    We have been tasked with making 12 nuts with a 5 1/2″ – 4 thread and the spec was provided ASTM A194 2H. The old nut was made out of 4140 Q&T plate, 6 inches thick. The engineer said that is why the nut failed and asked for a 1045 nut. We have not had any luck sourcing 1045 in a 10 inch round and are looking for a suitable substitute. What is a material that we can get, that big, that we can fulfill the ASTM A194 2H requirement with? Can ASTM A194 2H be applied to a nut that big?

    @David- The A194 standard, and all fastener specific grades stop at 4″. However, that doesn’t mean that you cannot ever make a nut larger, following the same guidelines. You should be able to find 10″ 1045 rounds without too much trouble and can then machine and heat treat per the A194 requirements.

    Hi, If ASTM A194M Grade DH nut can substituted for ASTM A563 Grade DH nut, then can it substituted for ASTM A563 Grade A?

    @Carlos- There are many grades within both A563 and A194, and they each have their own specific markings, or lack thereof. More often than not, the A194 nuts will be heavy hex and have a washer face, but there are exceptions. A563 nuts can be standard hex, heavy, jam, square, and thick pattern, although the bulk of what is in the marketplace is standard hex and heavy hex. If you have a more specific question, we are happy to try and answer it, but because there are so many different grades and types, it is hard to go through them all.


    @Alejandro- ASTM no especifica qué tuerca utilizar con los pernos A193 B16. A194 2H sería aceptable, pero queda en manos del ingeniero del proyecto para determinar qué es lo mejor. A194 gr.7 o g.16 también están permitidos.

    Can a Grade 5 bolt (SAE J-429) galvanized be used with an galvanized Grade DH Heavy Hex nut? The DH is is much stronger grade than the grade 5. The only concern I have is meeting the minimum of grade 5 strength.

    @Khan- Normally an SAE J995 grade 5 nut would be used, but as those are hard to find in a galvanized condition, an A563 grade DH will be more than sufficient. The proofload of the DH nut exceeds the tensile strength of the grade 5 bolt.

    “An A194 Grade 2H nut can always be substituted for an A563 Grade DH nut.” Is this still true if they are galvanized?

    @Mark- Yes, it is true, however the standard says that when substituting a galvanized A194 2H nut for a A563 DH nut, the 2H nut must have a colored wax applied to it, as is the requirement for DH nuts.

    The Nut Compatibility Chart is quite useful, but maybe you could also add an updated pricelist somewhere on the site?


    @Kasper Thank you for the suggestion. Unfortunately, we do not publish any pricing on our website. We are not a full-line fastener distributor. We are a custom bolt manufacturer and typically sell nuts as accessory to bolts that we are manufacturing. Nuts are typically priced with the bolts as a unit. If you require a price for nuts alone, please contact one of our salespeople directly and we will be happy to provide you with a price quote.

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