Tips for Choosing Fastener Material

Fastener Design Tips part 5

By far the workhorse material of the fastening world is carbon or alloy steel, often plated or coated to resist corrosion in service. But, is this material suitable for all designs? What about cast iron, stainless steel, aluminum or even carbon fiber? If we make poor choices on material or fastener finishes, we can be setting our joints up to fail. Let’s take a brief look at each of the aforementioned materials:

Joint Materials Recommended Fastener Material Recommended Fastener Finish Comments
Plain steel Plain carbon or alloy steel Plain finish
Cast iron Plain carbon or alloy steel Plain finish
Aluminum Aluminum alloy or stainless None Zinc flake coated plain carbon steel may also be used
Copper Copper None


Stainless is suitable
Stainless steel Stainless steel None
Zinc die cast Plain carbon steel Zinc plated
Carbon fiber Stainless steel

It is ideal to match the fastener material as closely as possible to the joint material not only to guard against galvanic corrosion, but also match the thermal expansion and contraction of the materials as they cycle through different temperatures.

There are also specialty fastener materials designed specifically for high temperature service.


For more information on which fastener material is right for your design, check out www.bossard.com or contact us at ProvenProductivity@bossard.com.

Doug Jones
Applications Engineer

January 18, 2019
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What You Need to Know About Grades and Property Classes

Fastener Design Tips part 4

Whether designing in inch or metric fasteners, you need to be aware of the grade (inch) or property class (metric) of your fasteners. Below is a matrix that helps you compare the difference between the two:






When designing with nuts and bolts, grades and property classes of hardware should match. However, higher strength nuts may be used with lower strength bolts. The nut must always be stronger than the bolt for safe and proper joint design, so using a lower strength nut with a higher strength bolt is asking for trouble.Typically, as strength increases, so does price. It is also important to note that stronger is not always better. High strength fasteners tend to be less flexible and often require better tightening control to take advantage of their strength.

Finally, strength of washers is often overlooked. The purpose of using a flat washer under a hex head bolt or nut is to spread the load and increase the surface pressure limit of the bearing surface. If non-hardened washers are used with hardened bolts, the hex head can dig into the face of the washer, allowing the clamp load to settle and the joint to loosen.


For more information on fastener grades and property classes, visit www.bossard.com or contact us at ProvenProductivity@bossard.com.

Doug Jones
Applications Engineer

January 11, 2019
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7 Factors to Keep in Mind When Selecting a Fastener Finish

Fastener Design Tips part 3

Many engineers will put great thought into selecting the proper type of fastener for their design but overlook the importance of the finish. When selecting the best finish for your fasteners, it is wise to consider the following factors:

  1. Safety – The incorrect finish could contribute to a failure of the fastened joint
  2. Corrosion protection – What is the expected service life of the part and the service condition?
  3. Resistance to handling damage – How do nicks and scrapes from handling and wrenching affect the finish?
  4. Criticality of the joint – Will the assembly fail if the joint comes loose? What are the consequences of an assembly failure?
  5. Functionality – Will the finish prevent my fasteners from assembling due to thread or recess fill?
  6. Availability – Is the finish readily available?
  7. Cost – Is the finish cost effective for my assembly?

There are many exotic coatings that have been developed for specific applications, with more being produced every day. Some of the most commonly available finishes are:

  • Electrodeposited Zinc (“commercial” zinc)
  • Electrodeposited Zinc Nickel
  • Mechanical Zinc
  • Zinc Flake
  • Hot Dip Galvanized
  • Epoxy Electrocoat


For more information on fastener finishes, visit our website at www.bossard.com, or contact us at ProvenProductivity@bossard.com.

Doug Jones
Applications Engineer

January 04, 2019
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Why You Should Pay Attention to Fastener Head Styles

Fastener Design Tips part 2

Choosing the proper fastener head style often boils down to either the engineer’s preference, what’s currently popular, or what’s needed for a very specific (non-standard) use. All of these situations can be dangerous and costly.

Internal Recess Drives

For internal recess drives, the most commonly available styles for smaller machine screws (1/4″ or M6 and smaller) are slotted, cross recess (Philips), cross recess (Pozidriv), Torx and Torx Plus. Internal hex drives are common in what we refer to as socket head screws, but they are intended more for tooling than for use in production. The matrix below should give you some points to consider when choosing an internal drive screw:

Slotted Philips Pozidriv Torx Torx Plus
No tool required* BEST NR NR NR NR
Consumer assembly OK BEST NR** OK NR**
Production hand assemble NR NR OK OK OK
Production power assemble NR NR OK OK BEST

*No tool required: In some designs, such as access doors on equipment, tools may not be readily available, so anything from a coin to a car key may be used to rotate the slotted head and gain access.

**NR: Pozidriv and Torx Plus drives are easily confused with Philips and Torx, even though they require different drivers. For consumer assembly, it is recommended to steer away from these.

Internal Recessed Drive Screws

For internal recess drive screws, the head style is imperative to consider. Many options exist, but not all are readily available. The most common head style is the pan head and it is available in nearly every size up to 1/4″ or M6. Less common styles are round head, cheese head, fillister head, hex head and hex washer head.

Larger Screws

For larger screws, hex head, hex flange head and hex socket head are the most common styles available. Hex socket heads are generally only used when there is a clearance issue where a socket will not fit on the head to drive it. Hex flange screws are generally more expensive than hex heads, but with their larger bearing surface, they can often eliminate the need for washers which can ultimately lead to a cost savings. Hex heads may be used without washers when bearing up against a very hard surface with a properly sized hole, but in many cases the surface pressure limit of the mating part is not high enough to support the load without adding hardened washers or a flange.


For more information on choosing the correct head style for your next design, check out our website at www.bossard.com or contact us at ProvenProductivity@bossard.com.

Doug Jones
Applications Engineer

December 28, 2018
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How to Design Soft Joints the Right Way

Fastener Design Tips part 1

Product engineers seldom receive training on fasteners, so some common mistakes are made in the design phase. The next five blogs will focus on some of these common mistakes.

What are Soft Joints?

A joint is considered “soft” when one or more of the materials being joined together is softer or weaker than the fasteners used to secure the joint. This may result in low preload which could lead to loosening or fatigue failure depending on the outside forces acting on the joint. Some examples of soft joints are gasket joints and plastics.

Gasket Joints

These are soft joints which sandwich a soft gasket material between two surfaces to seal against leaking. They must not be over tightened, or the gasket could fail. Over time, these gaskets can break down and begin to leak or allow the fasteners to loosen. An alternative method to help prevent failure of this joint is to design a step or groove in the gasket surface which allows the gasket material to compress and seal. This provides the hard surfaces to contact one another and achieve a higher clamp load, once again making a hard joint.


Many designs now incorporate plastics, which can be tricky to assemble without cracking. When attaching plastics to metal, the use of a shoulder screw or some type of compression limiter that prevents too much stress on the plastic material can be incorporated. Another alternative is threading specialty screws such as Delta PT® screws directly into the plastic. With the proper hole size and design, this method has been proven to be highly effective and economical.


For more information on soft joints, or for help with the assembly of your next great design, visit our website www.bossard.com or contact us at ProvenProductivity@bossard.com.

Doug Jones
Applications Engineer

December 21, 2018
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Locking Fastener Methods to Secure Your Application: Nylon Patches & Plugs

Locking part 3

Part three of our series on fastener locking methods will focus on nylon patches and plugs.

Nylon Patches

Nylon patches have some similarities to adhesive patches as they are both applied prior to arriving at the customer and they cannot be forgotten, but this is where the similarity ends.

Nylon patches are a hard, nylon material that is applied as a powder, and then melted into the threads with heat. The nylon material is typically NOT a 360° patch, but only applied on one side of the threads. The material is soft enough to form threads into it during assembly, but hard enough to create additional friction on the opposing side of the patch. This patch has some re-usability as it does not cure like an adhesive after assembly, but remains hard. Most manufacturers claim some locking effectiveness up to 3 to 5 times of complete dis-assembly and re-assembly. Applications which require minute adjustments without complete dis-assembly can benefit from this style of patch.

nylon patches








Nylon Plugs

Nylon material can also be added to the threads in the form of plugs or strips.

nylon plugs

nylon plugs 2







This method of application requires machining of the screws and pressing in the nylon plug or strip. While slightly more expensive to manufacture, some customers still prefer plugs over patches and believe they achieve improved performance with this style.

Some notable advantages of nylon over adhesive are a longer shelf life under ideal storage conditions and the possibility to re-use.


For more information on nylon locking features, or to help you decide which locking method is right for your application, check out www.bossard.com or contact us at ProvenProductivity@bossard.com.

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Doug Jones
Applications Engineer

November 30, 2018
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How the Titanic and the Iceberg Relates to Fasteners

Titanic Fasteners

When thinking about the tragedy of the Titanic, it is common to remember one of the major causes of its sinking: the iceberg. An iceberg is deceiving as it hides about 85% of itself below the surface of the water, making one believe that it is much smaller than it really is. The same can be said for the true cost of a fastener.

Factors of Fastener Cost

Fastener costs that can often be hidden below the surface may be labeled as an “activity cost”:

  • Purchasing
  • Receiving
  • Quality control
  • Put on stock
  • Picking and preparation
  • Checking invoices/payments
  • Yearly stocktaking

These activities have a cost associated with them for each part number in your Bill of Materials (BOM). By reducing part numbers in your BOM, you can cut your total fastener cost considerably. Don’t let your ship sink! Check out the Bossard Cost Savings Calculator, which allows you to calculate your potential savings by making Bossard your preferred supplier. Contact us at ProvenProductivity@bossard.com for help chipping away at your iceberg!

For more shopping options click here.

Doug Jones
Applications Engineer

November 09, 2018
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Why You Should Be Prepared for Industry 4.0

You may be hearing about the fourth industrial revolution, otherwise known as Industry 4.0. What does this mean? Ever since technology became integrated into the workplace during the third industrial revolution, companies have become more efficient.

To keep up with the ever-changing industry, more and more companies are using digitalization to streamline their systems. Now that we are getting deeper into the technological age, the integration of advanced technology such as cloud computing, 3D printing, artificial intelligence, and so much more is being integrated into the workplace.

What does this mean for you and your company? This means utilizing advanced technology and implementing it into the workforce or workplace. Industry 4.0 and IoT will create transparency which creates maximized efficiency and reduced downtime.

Bossard has created Smart Factory Logistics which keeps you at the cutting edge of the industry. If you would like to learn more about Industry 4.0 and manufacturing, check out our other pages such as the 7 steps to get ready for Industry 4.0 and digitalization or how will Industry 4.0 impact your supply chain?.

January 05, 2018
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Why Process Control is Important for Fasteners

How Important is Process Control for Fasteners

Many fastener manufacturers are faced with several different customer requirements or international standards. This leads manufacturers to create sampling plans to detect nonconforming product during mass production or final inspection. There are also several different AQL (Acceptance Quality Limit) levels according to batch or lot sizes. Do you think relying on final inspection sampling is the best idea? Even if they choose various samples from multiple bins of the same batch?

Fastener manufacturers are no different than any other industry. Speed, delivery, and quality are key, and most companies have been driving lean methodologies and efficiency tools into manufacturing processes. But does this have a negative impact on quality? Maybe, but most fastener manufacturers do still maintain minimum sampling plans that are fairly aligned with some international standards for mass production.

So what is a good detection method to minimize nonconforming product during the manufacturing process? Contact us through ProvenProductivity@bossard.com, and see what quality processes we encourage Bossard manufacturers to use to ensure quality fasteners for our customers.

Tony Peters

Quality Manager

October 27, 2017
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6 Types of Bolt Failure and How to Prevent It

Designing fasteners into your application requires a complete analysis of the joints to make sure nothing was missed. Understanding the types of failures that can occur will help with this analysis. Read on to see how to prevent bolt failure.

Failure Type of Failure Solution
  Overloading (stretching)

– Make sure that the appropriate material and grade was used

– Make sure your design is well understood and that the bolts are not overstressed


– Make sure that the appropriate material and grade was used

– Make sure your design is well understood and that the bolts are not overstressed

– Make sure that the fasteners are well-tightened


– Use a lubricant

– Avoid fastener misalignment

– Avoid high speed installation – keep installation speeds low

– Avoid rough surface – smooth finishes

[1] Shearing

– Make sure to re-evaluate tightening strategy

– Threaded section in shear plane – use shank instead

[2] Galvanic corrosion

– Avoid use of dissimilar metals

– Prevent moisture entrapment

– The fastener should be the cathode (more noble)

  Hydrogen Embrittlement

– Eliminate susceptible alloys, hydrogen, stress (service or residual)

– Use non-electrolytic platings

– Increase bake times

– Risk is never eliminated


For further information on these or other types of bolt failure, please feel free to contact us at ProvenProductivity@bossard.com


Fadi Saliby
Technical Sales Director


[1] http://www.learneasy.info/MDME/MEMmods/MEM30006A/Bolted_Joints/Bolted_Joints.html

[2] https://en.wikipedia.org/wiki/Corrosion

September 15, 2017
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