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:
- A307 Grades A and B
- A449 Type 1
- A325 Type 1
- A354 Grades BC and BD
- A490 Type 1
- F1554 Grade 36, 55, and 105
The compatibility of nuts for various grades of bolts can be verified with our Nut Compatibility Chart.