Finished Hex Nuts

a-hex-nutFinished hex nuts are the most common type of nut. Finished refers to the dimensional standard. Except for some smaller sizes, the width across the flats of the hex is one-and-a-half times the nominal diameter. Thickness of finished hex nuts is approximately 90% of the nominal diameter.

In modern terminology, these parts are usually referred to as regular nuts or simply hex nuts. However, as we at Nickel Systems are old-timers in the fastener business, we still refer to these parts as finished hex nuts.

Nickel Systems maintains an inventory of hex nuts in Hastelloy® (Alloys C276, C22, B2), Carpenter® 20 (Alloy 20), Inconel® 600 (Alloy 600), AL6XN®, Duplex 2205, Nitronic® 60 (A194 8S – Finished Pattern), 317L Stainless, 18-8 Stainless and 316 Stainless in stock at all times. Other alloys currently maintained in hex nut inventory include Nickel 200, 330 Stainless, Hastelloy® B3 and 904L.

Heavy Hex Nuts

Heavy hex nuts are used when more “beef” is needed than in standard hex nuts. Often heavy hex nuts are used in high temperature and high pressure applications, particularly those involving flanged joints. Generally the width across the flats is 1/8 of an inch larger than common hex nuts. The thickness of heavy hex nuts is equal to approximately the nominal diameter, which is about 10% thicker than a regular hex nut.

ASTM (ASME) A194 is one specification that is often sited in connection with heavy hex nuts. Several different materials are covered by ASTM A194. Nickel Systems can supply heavy hex nuts conforming to: ASTM A194 2H (1045 Steel, Heat-Treated), ASTM A194 Grade 6 (410 Stainless), ASTM A194 Grade 8 (304 Stainless), ASTM A194 Grade 8C (347 Stainless), ASTM A194 Grade 8M (316 Stainless), A194 Grade 8R (Nitronic® 50), A194 Grade 8S (Nitronic® 60) and A194 Grade 8T (321 Stainless).

Nickel Systems is not limited to materials covered by ASTM A194. We maintain heavy hex nut inventory in Hastelloy® C (Alloy C276), Carpenter® 20 (Alloy 20) and Duplex 2205. Metric sizes and other alloys can be provided.

Finished Hex Jam Nuts

Jam nuts, sometimes referred to as thin nuts, are approximately 65% as thick as a standard hex nut. They were originally used to jam against another jam or full height nut and provide a locking feature.

Heavy Hex Jam Nuts

Heavy hex jam nuts are not very common. They are used where a large bearing surface is required and minimal clearance or thread engagement is available. Nickel Systems can provide heavy hex jam nuts by cutting full height heavy hex nuts in our shop.


Locknuts are used where there is a significant probability that a nut will loosen over time because of vibration or frequent temperature changes.

When the danger of corrosion is not too severe and 18-8 or 316 Stainless is adequate for fastening we would offer nylon insert locknuts. These nuts feature a nylon ring that compresses against the bolt threads as the nut is tightened.

In instances where common stainless would not be adequate to withstand corrosion and a locknut would be required, we would recommend a top-lock nut. These nuts are produced by crimping the top thread of a standard hex nut. When top-lock nuts are assembled, they should spin freely until the lead thread of the bolt meets the distorted thread in the nut. The more the nut is torqued from this point, the greater the effort for disassembly becomes.

Nickel Systems stocks nylon insert locknuts in 18-8 and 316 Stainless. We stock some top-lock nuts in Hastelloy® C (Alloy C276) and Carpenter® 20 (Alloy 20). Within a reasonably short lead-time, we can provide top-lock nuts in Hastelloy® (Alloys C22, B2), Inconel® 600 (Alloy 600), AL6XN®, Duplex 2205, Nitronic® 60 (A194 8S – Finished Pattern) and 317L Stainless, as we stock standard hex nuts in these materials.