Fastener Technology

What is a “special” fastener?  It is important to differentiate between standards and specials when identifying fasteners to be purchased or quoted.  If a fastener can be defined in a simple text description, it is not “special” and should not require a blueprint. See the following standard metric fastener description per ISO 8991:

Hexagon head bolt ISO 4014 – M12 x 80 – 8.8 – A2C

Customers will often create prints for fasteners and detail every dimension. This slows down the quoting process because every dimension has to be verified as “standard” or “special” by every manufacturer who looks at the print. Best practices for specials is to dimension only those items that are non-standard, and reference a dimensional standard for those items which are not special. For standard parts, a print is not needed, so save yourself the trouble and don’t make a print!

Contact us through ProvenProductivity@bossard.com with any questions or more information regarding standard and special fasteners and components.

Doug Jones
Applications Engineer

Email: djones@bossard.com

A Metal Locking Tie (MLT) is a cable bundling product that is made of stainless steel. It has a self-locking head to increase efficiency in installations. The head locks into place at any place along the tie body to provide convenience and ease for your toughest jobs.

Uses & Performance

While on the job the smooth surface and rounded edges protect the worker and increase safety on the job site. This product can be used for outdoor, indoor, and underground applications, including direct burial. The Metal Locking Tie is a strong durable method of cable bundling. Metal Locking Ties can be used for both general-purposes and corrosive environments.

Self-Locking Head

This patent design has an aggressive locking head for a quicker locking, tighter installation. With a unique locking ramp this assures the self-locking head is locked in any positon. The strengthening ribs increases the locking hold for safety and security on the job site.

Check out more about Metal Locking Ties visit at www.bossard.com. For more information, or if you have any questions please reach out to us at ProvenProductivity@bossard.com.

Nut vs. bolt is a common matchup among engineers. Engineers design joints to withstand a certain amount of clamp load, but clamp load is not easy to measure when assembling a joint, so torque is specified. The assembler knows they have a “good” joint when the proper torque is achieved, indicated by an audible click of the wrench, or a green light.

Now consider what happens if too much torque is applied, and the joint starts to yield. If the bolt is the weaker joint member, it will begin to stretch, necking down in the threaded portion, eventually breaking before it ever reaches the prescribed torque. In this case, the assembler stops his work and raises a red flag – something is wrong, and the problem is addressed.

In the second scenario, we again apply too much torque and the joint starts to fail, but the nut or tapped hole begins to yield instead of the bolt. As the internal threads start to fail, friction and heat are created, and galling or seizing of the threads may occur.

In some instances, we may achieve the click or green light, indicating that we have a “good” joint and the assembler moves on to the next job, not realizing that yielding has occurred. Once the product is used, the service loads may be enough to cause a catastrophic failure of the already compromised joint.

Which is stronger: the nut or the bolt? As a rule of thumb, always make sure that the nut (or nut member) is stronger than the bolt.

Check out our thread engagement length calculator on www.bossard.com to make sure that your joints are designed properly.

One of the keys to understanding the metric system is the understanding of its tolerance system. There is simply no manufacturing method that enables production to perform to exact dimensions. In the inch system, tolerance is mainly done by giving minimums and maximums.

The ISO tolerance system was created by the International Standard Organization in 1948. Originally it was developed for fits and is still mainly used in this manner. It is based on IT Grades which are base tolerances from which all the individual tolerances are derived.

The system is composed of a letter and number base.

The letter indicates the location of the tolerance (whether plus or minus, how much plus, how much minus).

The number indicates the tolerance range. The bigger the number, the bigger the spread between the minimum and the maximum, and therefore the larger the tolerance range.

Download the Bossard Technical section for basic tolerances and tolerance fields, or email ProvenProductivity@bossard.com with any questions regarding tolerances.

Joe Stephan
Application Engineer

What is meant by the term “standard fasteners”? Generally, it refers to fasteners that are stocked on the shelf rather than made to order, which translates into shorter lead times. Often, looking at a catalog will give you a pretty good idea of what is available, but below are some general guidelines and a few exceptions to note.

Standard fasteners lengths follow a pattern. For short fasteners, typically lengths under 20mm are available in 8, 10, 12, 16 and 20mm. Lengths from 20mm to 70mm are available in 5mm increments, while lengths over 70mm skip to 10mm increments. For example, you can get an M10 x 65 or M10 x 70, but the next available length is M10 x 80.

Width Across Flats (WAF) for hex products can be a bit confusing. DIN standard hex head parts are generally stocked more than ISO standard hex heads. This can be significant in diameters M8, M10 and M12. DIN parts are 1mm larger WAF for these sizes, requiring a larger wrench to drive them. Other diameters share the same WAF for both standards. Many distributors consider DIN and ISO hex heads as equivalent even though the heads may be a slightly different size.

Metric socket head products are not readily available in all property classes. Socket head cap screws are offered in 8.8 and 12.9, but not in 10.9. Flat socket head cap screws and button socket head cap screws are available in 10.9, but not in 8.8 or 12.9. Exceptions can be made with special orders, but these are not considered standard.

Contact us through ProvenProductivity@bossard.com to learn more about standard, readily available fasteners.

Doug Jones
Applications Engineer
djones@bossard.com

When selecting fasteners that are to be assembled together, it is important to consider their strength compatibility. The nut should always be stronger than the bolt, so when using higher strength bolts, such as metric class 10.9, make sure to use the correct, corresponding nut. In this case, a class 10 nut would be correct. Stronger nuts may be used with lower strength bolts without any problems.

Strength of washers should also be considered, but are often overlooked. Using non-heat treated washers with heat treated hex head cap screws can cause joint settling as the relatively small bearing surface of the cap screw can embed itself into the soft washer over time, causing a loss of clamp load.

Standard metric flat washers have class designations that can be paired with heat treated bolts. Below is a compatibility chart that will help you make the right choice.

Check out the “Technical Resources” section at www.bossard.com for more information on selecting the proper fasteners, or reach out to us at ProvenProductivity@bossard.com with any questions.

Doug Jones
Applications Engineer
djones@bossard.com

When doing research for your bolted joint it is important to understand the coefficient of friction of the finish of the fastener. There are many different options for coatings that will give you different ranges in values. Typically, those values are tested to a certain specification. Whether it’s an OEM specification, or per the ISO 16047 standard, each one can have minor differences (if you have questions on standards reach out to a Bossard engineer). So what do those values actually mean and how are they relevant to your joint?

Most of the testing that is done to validate the values of the coating is done on M10 surrogate bolts with a standard hex head cap screw. They are tested in lab conditions with either a plain finish washer or nut that is cleaned and degreased or with different variations done in a lab setting. The cause for concern is using those values in your joint. The values can change depending on your bearing surface and your mating threads (material, surface condition, lubrication, bearing surface area, etc.). As stated in previous Proven Productivity blog posts, it’s important to understand the relationship so you prevent costly errors down the road.

That is why we at Bossard always recommend doing bolted joint testing. We have the capability to perform joint testing so we can help you better understand the coefficient of friction and the torque tension relationship in your joints. We can perform testing onsite at your facility or you can visit one of our engineering design centers.

Contact us at ProvenProductivity@bossard.com for more information.

Jon Dabney
Application Engineer
Jdabney@bossard.com

Take a minute to think of some of the most amazing mechanical marvels we have today: electric vehicles, exo-skeletons, cell phones, wind turbines, and many more. What do most of them have in common? They are all held together with some type of fasteners.

Now think about your product. What happens if the fasteners fail during use? At best, the customer is not happy and may look at other brands for their next purchase. At worst, damage to property or personal injury could result.

So, why are fasteners always the last thing we think about in our design? It’s true that assembly is the last step in the product design process, but fastener selection should be carefully considered in the early product design stages to ensure the best and safest product. Early fastener selection is also associated with time and cost savings making your process more lean and efficient.

Not sure what is the best choice? Have questions about what’s readily available or what’s new in fastener technology? Contact your fastening solutions provider to help you select the best hardware for your project. Don’t wait until two weeks before production starts!

Contact ProvenProductivity@bossard.com for information about the latest and greatest hardware innovations, and get help with your next project!

Doug Jones
Applications Engineer
djones@bossard.com

You’ve spent months on your design doing careful analysis and selecting the right materials. You are finally getting close to production – but wait, you haven’t selected a fastener supplier yet. You need mostly standard fasteners, except for those few specialty print parts. It’s just fasteners; how hard can it be?

The next step is to turn over your fastener list to the buyer and have them find the cheapest hardware they can negotiate to save a few pennies on the product. After all, it doesn’t matter where they come from. All fasteners are the same, right?

This scenario may be a bit harsh, but is all too often true. If manufacturers are making standard fasteners, they should be using the same fastener standards. Unfortunately, some manufacturers take short cuts to keep costs down in this highly competitive market. Some low-cost providers may make perfectly good fasteners 90% of the time, but is 90% good enough for your design? Assembly issues, failures in the field, warranty claims costs, and poor customer satisfaction when a new widget breaks or doesn’t perform as advertised can be very expensive and time consuming.

My advice is this: know where your fasteners are coming from. Here are some questions you can ask yourself before selecting a supplier:

• Does the manufacturer have good process controls?
• Are they tracking reject rates both internally and externally?
• Are they subcontracting fastener finishes or heat treatment?
• Do the subcontractors have good process controls?

Contact us through ProvenProductivity@bossard.com and see what steps we take to ensure good quality fasteners.

Doug Jones
Applications Engineer
djones@bossard.com