PROCESS PIPING PRODUCTS

A Brief Primer on Stainless Steel Fasteners

Looking at the various types of stainless steel fasteners available and common applications for their use

Stainless steel fasteners are a popular component for a wide range of applications across an equally diverse range of industries.

While picking the right fastener might not have immediate signs or benefits to some, choosing the wrong fasteners can be catastrophic.

This guide will look at popular fastener types and designs, which grades of stainless steel are best suited for specific applications or environments, additional considerations when choosing the ideal fasteners, and standards you might reference to ensure safety and long-term performance.

What is a Fastener?

In most cases, the stainless steel fasteners we’re discussing in this guide are likely a form of screw or bolt.

They’ll consist of a head, a shaft, and a threaded end.

Diameters and lengths vary greatly to help you find options to suit nearly any application.

In most cases, heads are either hex-shaped, socket-shaped, or screw-topped with a driving recess.
However, studs do not include a head, instead relying on a threaded or smooth shaft that can interface with other fastening components on both ends.

When combined with other parts, such as domed nuts, standard nuts, flat washers, lock washers, and wing nuts, fasteners like bolts, screws, and studs can hold components in place, attaching sections of piping, and accomplishing a wide range of connection and placement functions.

Why Choose Stainless Steel Fasteners?

Stainless steel’s outstanding strength and corrosion resistance make it an ideal option for various applications where carbon steel or other materials might quickly fail or degrade.

While treatments or plating can improve the corrosion resistance of other metals, stainless steel fasteners and components allow you to skip the added cost or durability concerns associated with these processes.

Stainless is also a self-healing product with minimal maintenance requirements so long as oxygen is readily available in the use environment.

The long service life and minimal upkeep justify the added cost associated with stainless steel for many use cases.

Popular stainless steel fasteners we regularly stock include:
  • Hex head bolts
  • Hex nuts
  • Lock washers
  • Flat washers
  • Redi-Rod (threaded rod)
  • Wing nuts
  • Cotter pins
  • Full threaded studs
  • Socket head capscrews
  • Socket set screws
  • Button head socket capscrews
  • Flat head slot machine screws
  • Round head slot machine screws
  • Round head socket wood screws
  • Round head socket sheet metal screws

 Which Stainless Steel Grade Are Best for Fasteners?

While all stainless steel bolts, screws, studs, caps, bolts, and other fasteners will provide some corrosion resistance, choosing the right grade is essential to optimizing service life and cost.

If you’re not sure where to start, consider the following options.

By far, 304 stainless fasteners are the most commonly produced and used fasteners across a range of industries.

From piping flanges and kitchen equipment to attaching ornamental tubing products—such as stainless steel handrails—or sealing connections with pressure vessels, 304 is an affordable yet reliable option for most parts.

If you require higher corrosion resistance, grade 316 stainless steel fasteners and components provide options for saltwater applications—such as oil and gas processing—or processes involving frequent exposure to caustic chemicals—such as chlorides.

However, they do so at a higher cost.

So unless you need the additional resistance, you might be spending more than required.

Both of these grades are austenitic stainless—meaning that, as a rule of thumb, the hardware will be magnetic, not heat treatable, and acceptable for cold forming.
If you need non-magnetic or heat-treatable fasteners, consider 400 series martensitic grades such as 410 and 420. However, remember that these grades are harder to cold form if required.

You’ll also find fasteners made from other more exotic alloys and grades.

However, unless they offer a specific benefit to your application or use environment, they may not be the most cost-effective option for your project.

Still, this level of flexibility makes stainless steel a popular alloy across a range of industries.

Related Guide: Stainless Steel Grades and Families Explained.

Other Considerations when Choosing Stainless Steel Fasteners

While the grade you choose is important, it’s only a single variable in the decision-making process.

For example, the bolts used to tighten and seal a flange, the screws used to secure a pipe to a wall, or the nuts and bolts used to connect instrumentation to a vessel are all likely different.

Although you should always consult with a qualified engineer or product specialist to confirm your exact needs, the following considerations can help you narrow down the pool of options for your use case.

Head Types and Torque Concerns

While studs will provide a range of tightening and capping options, bolts and screws are less flexible.

However, the fact that the head is machined as part of the component can also provide strength and durability benefits.

Hex and socket heads typically provide the most durable design.

As such, they are ideal for high torque scenarios and use in high-pressure applications.
Screw heads, while typically less able to withstand higher torques at similar dimensions as hex and socket heads, provide yet another layer of flexibility with the range of driving recess designs available.

For example, Torx, Phillips, slotted, and square recessed will all provide different levels of torque resistance as well as change the tools required to tighten or loosen the fasteners.

Thread Types

Outside of head types, thread type is most likely to impact the suitability of a stainless steel fastener for a given use case.

Coarse threads are the most common, allowing for rapid rotation.

It is suited to even low-strength metals.

However, it might not perform as well as fine thread fasteners of similar specifications in high-tension or high-pressure implementations.

Fine threads, as mentioned above, improve performance under high tension or pressure.

However, they require more rotations to tighten and run a greater risk of thread damage or galling due to their thinner threads.

8-thread series fasteners are a specialized thread pattern typically used in larger diameter fasteners of an inch or greater in diameter.

Bolt or Stud Length

When choosing a fastener, it’s critical to consider all the other components required for properly installing and operating your fastened components.

This will help you determine an ideal length that allows for effective tightening while remaining within system design tolerances and avoiding the need for further machining and fabrication, which might damage or compromise the fasteners.

For example, when connecting flanges, bolts or studs often need to have enough length to accommodate a washer, the flange, any gasket or interfacing, the opposite flange, another washer, and the nut, cap, or wingnut securing the connection.
If you choose a fastener that is too short, you risk failing to connect or compromising the threading as you attempt to gain traction on too small of a threaded section.

Likewise, if you choose too long of a bolt or stud, it might not fit within the clearance between the flange and other components. It could also create safety hazards for workers.

Even if these aren’t an issue, tightening or loosening the flange for maintenance will require more effort than it should.

Similar concepts apply when choosing fasteners for pipe supports.

End Point Design

While most studs will end with a flat termination on each end, hex bolts and screws can feature a variety of ends—including flat, self-tapping, and self-drilling types.

The ideal option for you will depend on your intended use. In most cases, this isn’t simply a matter of ease of use but is outlined in standards and regulations.

Fastener-Related ASTM Standards


Key Takeaways

  • Common stainless steel fastener types include bolts, screws, nuts, studs, wingnuts, flat washers, and lock washers.
  • Stainless steel’s self-healing corrosion resistance provides an affordable and lower-maintenance alternative to treated or plated fasteners made from other materials.
  • 304 stainless fasteners are the most commonly produced and used fasteners across a range of industries.
  • If you require higher corrosion resistance, grade 316 stainless steel fasteners and components provide options for saltwater applications or chloride-rich environments. However, they do so at a higher cost.
  • If you need non-magnetic or heat-treatable fasteners, consider 400 series martensitic grades such as 410 and 420.
  • Hex and socket heads typically provide the most durable design when used in high-torque or high-pressure applications.
  • Screw head performance will vary based on the driving recess in use.
  • Coarse thread fasteners are the most common, providing rapid loosening or tightening and strong thread strength.
  • Fine threads improve performance under high tension or pressure but do so at increased risk of thread damage and increased rotation requirements.
  • 8-thread series fasteners are a specialized thread pattern typically used in larger diameter fasteners of an inch or greater in diameter.
  • When choosing a fastener length, it’s critical to consider all the other components required for properly installing and operating your fastened components.
  • If your fastener is too short, you risk damaging components or weakening the connection between your fastener and your piping or processing system.
  • If a fastener is too long, you could run into fitment issues or create an unnecessary risk of injury.
  • While most studs will end with a flat termination on each end, hex bolts and screws can feature a variety of ends—including flat, self-tapping, and self-drilling varieties.
Unified Alloys is a leading provider of stainless steel fastenerspipe products, and stainless steel materials throughout Canada and North America. If you’re looking for the perfect fastener for your next maintenance project or system design, call or e-mail today to speak with one of our expert sales analysts to see how we can help you!
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