Fastener Technology

Inch or Metric? Check the Head Marking!

Inch or Metric - Check the Head Marking

If you are like me and like to wrench on things, whether it’s fixing a car or repairing the snowblower, you probably have a set of inch and metric wrenches. Sometimes you can determine which set you need by the age or brand of whatever it is you are fixing. Anything made in the United States prior to 1980 is probably not using metric fasteners, while most other parts of the world have never used inch fasteners. If your project was manufactured in the US in the 1980s or 90s, you may see both inch and metric, which may drive you crazy unless you learn a bit about head markings.

Standard headed fasteners, both inch and metric, are required to have a grade or property class marking on the head if it has been heat treated. Also, on the head should be the manufacturer’s identification marking like the triangle in the pictures below. Inch fasteners define their strength (grade) by slash marks as indicated below for grade 5 and grade 8.

Metric fasteners define their strength (property class) with two numbers separated by a decimal point such as 8.8 or 10.9 which are the most common.







Property Class 8.8

So, next time you grab a wrench for a project, take a look at the head of the bolt to see which type of wrench you’ll need!

For more information regarding fastener markings, visit or contact us at

March 22, 2019
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Choosing the Right Fasteners for Your Railway Energy Supply Applications

Railway Products

When it comes to selecting the proper railway products, perhaps the most important component to consider is the materials you choose to use for the train’s energy supply. All of Bossard’s energy supply fasteners are designed to meet the highest safety protection and reliability standards. This includes high corrosion and vibration resistance, as well as built-in fire protection.

For instance, Bossard’s barb cable ties are specially made for railway applications. These versatile ties can be used wherever personal and asset protections are a priority. Made with a steel locking barb to ensure stable and strong bonding, they have an impressive durability.

To further prove our emphasis on safety, our resilient conical washers will not loosen due to crushing, wear, vibration, or even material expansion. We also offer wrap sleevings to organize and bundle pre-assembled cables in a flame-retardant, self-extinguishing, and halogen-free material that is built to withstand fire and heat. Similarly, our coating products are all manufactured to be safe, clean, and efficient with remarkable temperature and corrosion resistance. Plus, they come in a range of decorative hues to match whatever color scheme you choose.

When it comes to protecting your passengers and cargo, Bossard’s railway energy supply products have you covered in terms of reliability, quality, and a steadfast commitment to safety.

For more detailed information and to learn more about the quality products Bossard offers, download our complete Railway brochure here, or contact us directly at

March 15, 2019
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What Are the Best Fasteners for Railcar Body Applications?

Railcar Building

When it comes to railcar body products, Bossard recognizes the importance of keeping the installation process quick and simple. That’s why we supply special fasteners that are easy to install and just as easy to remove, allowing for a fast and stress-free installation process. All of our railcar body products are made of the best quality materials, have extraordinary corrosion resistance, and comply with high safety standards.

Railcar body materials not only provide structural stability for the train, but they are essential to safety as well. There is no room for error, which is why Bossard provides materials that can withstand high temperature, corrosion, and vibration to ensure a long-lasting product. For instance, Bossard’s slotted self-locking nuts are reusable and built to retain clamp load even in extreme conditions.

Permanent materials include our lock bolts, allowing fast and automatic installation, and our grounding studs, which are simple to install with our battery powered installation tool. These studs use bolts to discharge leakage current and have an excellent above average clamping range. Another product with enormous clamping force are tensioner nuts, which allow for simple and safe tightening through any hand tool. These nuts prevent thread galling and are a great economical option when mounting large bolts and studs.

Bossard offers only the best when it comes to railcar body products: safe, stable, affordable materials that are built to handle immense resistance and stress while still providing easy installation.

For more detailed information and to learn more about the quality products Bossard offers, download our complete Railway brochure here, or contact us directly at

March 08, 2019
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The ABCs of Interior Railcar Fasteners & Accessories

Interior Railcar Build

From luggage racks, to grab poles, to seats and folding tables, Bossard offers plenty of fasteners designed to improve the functionality and design of interior railway materials. In these types of products, endurance is the key to the safety of train passengers. Materials need to be able to withstand daily strain and even possible passenger vandalism. They need to be light, durable, and functional, which might sound like a tough combination to achieve, but Bossard’s high-quality fasteners and other products were expertly engineered to do just that.

Our railway interior products are all designed for functionality while keeping the comfort of the passengers in mind. Hinges for folding tables need to be long lasting while still maintaining a full range of motion. C-rail fasteners must be easy to shift and reuse and Bossard’s are the perfect combination of stable, yet flexible. Our threaded inserts are lightweight, but they boast impressive durability, making them a strong choice to use in thin materials.

Functionality doesn’t just pertain to ease of use—we also understand the importance of keeping everything looking sleek, smooth, and clean. Our fasteners for soft and composite materials can be mounted with adhesive or be completely embedded, providing invisible integration into the application material. Get rid of clutter with our cable tie plates designed to save you space while securely organizing wire bundles close to mounting surfaces. Many of our products also come in a variety of colors, allowing you to easily incorporate them into whatever color scheme you’ve chosen.

When it comes to choosing interior railway products, Bossard offers the complete package: reliable, sturdy materials that look clean, work smoothly and safely, and provide the best value for your money.

For more detailed information and to learn more about the quality products Bossard offers, download our complete railway brochure, or contact us at

March 01, 2019
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Using DELTA PT® in Thermoplastics

Using DELTA PT in Thermoplastics

If you’re in need of a reliable direct fastening thermoplastics screw guaranteed to provide calculable extra performance, look no further than DELTA PT®.


This strong but flexible screw is the result of many years of experience in direct fastening into thermoplastics. Through much study and practice, Bossard is now able to offer a high-quality product designed to make fastening jobs not only easier, but more cost effective.

The DELTA PT® screw offers many advantages when it comes to choosing a fastener for plastics. Due to its narrow flank angle, this screw minimizes radial stress, allowing unimpeded material flow and reducing heat buildup. This reduces the likelihood of costly damage to the plastic and ensures product quality will not be compromised.

Perhaps the most important characteristic of DELTA PT® is its unbeatable strength while still being flexible enough to keep the surface pressure low. Its optimized thread pitch enhances vibration resistance, consequently increasing the service life of the joint. DELTA PT® screws boast a high tensile strength, as well as a high torsional strength, meaning they are capable of withstanding stretch while still maintain great torque strength.

When using DELTA PT®, driving speed should be between 300-800 rpm and can be used with both air and electrical powered screwdrivers. They can be used in automated assembly, but should be specially defined and produced to meet the automated assembly quality.

For more information on DELTA PT®, contact us at

February 08, 2019
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Surface Finishing Stainless Steel

Surface Finishing Stainless Steel Intro

Even though we want stainless steel to always live up to its name, it doesn’t work perfectly as intended 100% of the time. Understandably, consumers get frustrated when their supposedly “stainless” steel shows signs of rust, and they have questions as to how it happened and how it can be prevented in the future. In the paper provided, we will give you information to help you better understand possible causes and the categories which can lead to problems with stainless steel. Often, a little basic knowledge and precaution can go a long way in the prevention of rust in your stainless material.

To have an in-depth conversation with one of our highly skilled fastener engineers, contact us at

February 01, 2019
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Locking Fastener Methods to Secure Your Applications: Additional

Locking part 5

Part five of our series on fastener locking methods will focus on some alternative locking methods not previously covered.

Serrated Flange Nuts/Bolts

Serrated flange nuts and bolts use serrations on the bearing surface to create higher friction and prevent loosening, primarily on sheet metal joints. Care must be taken to NOT use any washers with this hardware and to ensure serrations on both the nut and bolt to prevent any rotation. When designed correctly, joints using serrated hardware perform very well, but corrosion can be a concern if the hardware is installed after paint as some material can be removed during assembly and especially if removal is required.

serrated flange nuts and bolts







Double Nuts

Use of a jam nut (or thin nut) to “double nut” a joint has been around for many years, and can be a very effective method of locking a threaded joint. The assembly method and the use of two nuts for each joint may not be the most efficient, and many people do not install them correctly. When using a jam nut, the thinner nut goes on first, and the standard nut gets tightened to full torque on top, while holding the jam nut in place. This can make it tricky to induce the proper pre-load on the joint which is part of the reason this method is seldom used any more.

double nuts







Mechanical Thread Locking

Some manufacturers have come up with special thread geometry to create a mechanical locking in either the internal or external threads. Different from locking nuts, which starts with a standard thread, and deforms or damages it to create friction, these specialty threads are rolled or tapped into the fastener when the threads are initially formed, which provides greater consistency and a more predictable clamp load.

Tab Washers

Tab washers have multiple tabs which are bent both in opposing directions after assembly to lock the nut or bolt head into the mating surface.

tab washers







Castle Nuts

Castle nuts or slotted nuts have slots cut or formed across the flats to allow for a cotter pin to be passed through a cross drilled hole in the mating male threaded component. Often used on highly critical joints such as front wheel bearing assemblies on automobiles, this positive locking feature is a guaranteed, but costly way to secure a bolted joint.

castle nuts






Safety Wire

Generally used in aircraft, high performance automotive, or other high critical applications, these bolts and/or nuts will have holes drilled through the heads or flats. Safety wire can then be passed through, twisted and attached to neighboring fasteners to prevent rotational loosening.

safety wire







Questions? Want to learn more about locking fastener applications? Contact us at

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Doug Jones
Applications Engineer

December 14, 2018
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Locking Fastener Methods to Secure Your Application: Lock Nuts

Locking part 4

Part four of our series on fastener locking methods will delve into lock nuts, also referred to as prevailing torque nuts because they are not “free spinning” but require a prevailing torque to assemble them.

Many different styles of locking nuts have been developed over the years, but we will focus on two general categories: all metal lock nuts and nylon insert lock nuts.

All Metal Lock Nuts

All metal lock nuts start their life as free spinning nuts but pass through either a press or punch machine which deforms part of the thread to create friction during assembly. Classified as either top lock or side lock, it is a good idea to know the difference and determine the best style for your application.

Top Lock

Top lock nuts have a thread deformation at one end of the nut, meaning assembly can only take place in one direction. The most common type of top lock nut (often referred to as a stover lock nut) has a cone shape on top, making it easy to identify the top of the nut for directional assembly.

stover lock nut






Side Lock

Two-way lock nuts may be assembled in either direction, which allows them to be used in automated assembly. These nuts can be identified by the punch marks on the flats. It is common to have either one punch mark, or two punch marks on opposing flats.

two way lock nut




Nylon Insert Nuts

Nylon insert nuts use a non-threaded nylon ring which gets crimped into the top of the nut at the end of the manufacturing process. As the nut is assembled onto a bolt, threads form into the nylon ring at the top of the nut, creating resistance.

nylon insert nuts





Each style of nut has its advantages and disadvantages. All metal lock nuts can be used at higher temperatures than nylon insert nuts, but nylon insert nuts tend to have more consistent clamp load from lot to lot. All metal lock nuts typically require a wax on top of the normal zinc plated finish to keep from galling, which can result in some unpredictable clamp loads in critical joints.


For more information on locking nuts, check out or contact us at

For more shopping options click here.

Doug Jones
Applications Engineer

December 07, 2018
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Locking Fastener Methods to Secure Your Application: Adhesives

Locking part 2

For part two of our series on fastener locking methods, the focus will be on adhesives. In general, there are two ways to apply locking adhesives to a fastener joint. Liquid adhesive such as Loctite® can be applied to the threads at the time of assembly, or an adhesive patch can be pre-applied to the threads at the time of processing, prior to shipping to the customer.

Liquid Adhesives

The application of liquid adhesives can be done with a squeeze bottle, with a brush, or even rubbed on the threads with a glue stick applicator. One of the challenges with these types of application is getting the right amount on the threads to create the desired locking effect without wasting material. Some manufacturers of liquid thread locker have even developed precise metering guns to deliver the same amount of material for each application.

Liquid adhesives














Manufacturers of thread locking material will give recommendations on how much material and which delivery system makes the most sense for your application, but how does thread locking adhesive work?

The common thinking is that thread locking adhesives simply act as a glue, bonding the male and female threads together so that they cannot rotate loose. Although this is true to some extent, the real benefit to locking adhesives is that they harden after assembly and fill any gaps between the threads. Rotational loosening occurs whenever outside forces (such as vibration) acting on the joint cause a loss of friction in the threads and bearing surface. If the force and the frequency are high enough, air gaps in the threads allow for the loss of friction. Eliminating the air gaps with thread locking adhesive is a very effective way to prevent rotational loosening.

Pre-Applied Adhesives

Pre-applied adhesives prevent rotational loosening in the same manner as described above, but they are applied at the manufacturer as a patch. The adhesive material is microencapsulated so that it will not dry until the fasteners are assembled, crushing the microcapsules and releasing the curing agent.

Some advantages of pre-applied adhesives include:

  • No waste from over-application
  • Adhesive is in the same location each time
  • Cannot be forgotten by the assembler
  • No mess

pre-applied adhesives





A disadvantage of pre-applied adhesives is that they have a limited shelf life which needs to be monitored. If parts have been sitting for too long before assembly, the patch material may dry out and be less effective. Most pre-applied adhesives have a shelf life of 1 – 4 years.

Shop Tape Adhesives

For more information on which thread locking adhesive is right for your application, visit us at or contact us at

Doug Jones
Applications Engineer

November 23, 2018
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Locking Fastener Methods to Secure Your Application: Lock Washers

Locking part 1

This is the first of a five-part series about locking methods for fasteners – the first product we discuss is lock washers.

For joints subject to vibration and cyclical loading, maintaining clamp load and/or keeping the joint tight is one of the biggest fastener problems engineers face. As stated in previous blogs, the best joint design to ensure against loosening is a hard joint with a clamping range of five times the screw diameter, tightened to proper clamp load. When this is not feasible, using a locking fastener method is necessary.

First, let’s look at locking washers:

1. Split Lock Washers/Helical Lock Washers





Available at every hardware store for pennies a pound, these washers have a very limited usefulness as a locking fastener, especially with grade 5 or 8 fasteners (metric property class 8.8 or 10.9). Made of very hard spring steel with a small bearing surface area, the spring rate they produce (the amount of force to flatten) is far below the optimal clamp force of a grade 5 or higher bolted joint. This washer’s use should be limited to grade 2 fasteners, small machine screws or metric property class 5.8 and lower.

2. Ribbed Lock Washers

Ribbed lock washers Ribbed lock washer 2







These conical washers are made to work with higher strength fasteners. The first washer pictured has ribs on the convex side which creates friction between the bearing surface of the fastener (nut or bolt) and works well with grade 5 (metric 8.8) fasteners, but not grade 8 (metric 10.9). The higher strength fasteners have a higher surface hardness, and the ribs will not engage with the bearing surface, limiting their locking ability.

The second ribbed washer pictured above works well with grade 8 (metric 10.9) fasteners. The more aggressive, higher hardness ribs on both surfaces will engage with the harder material to create friction locking.

3. Wedge Ramp Locking Washers

Wedge ramp locking washers







This style of locking washer comes as a pair of washers glued together. The outer surfaces have ribs which are hard enough to work with grade 8 (metric 10.9) fasteners. The wedge ramps between the two washers lock together during tightening, but when loosening the joint, the washers rotate against one another, creating slightly more clamp load as they overcome the angle of the ramp.

It is important to note that any of these locking washers should NOT be used with flat washers, and if used with a bolt and nut joint, they should be on both ends. Rotational loosening caused by vibration will occur at the bearing surface with the least amount of friction, so flat washers should be avoided.

It’s also important to note that because these washers increase bearing friction, more torque may be needed to achieve your desired clamp load. Some washer manufacturers publish recommended torque values, but for critical joints, a joint study is recommended to arrive at your optimal setting torque.


There are many other styles of locking washers, but the ones above will get you through most situations. For more information on locking fasteners, visit us at or email us at

To shop latches, hinges, locks and accessories, click here.

Doug Jones
Applications Engineer

November 16, 2018
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