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Lean Bonding is an innovative new method of fastening composites and thin metal materials.  Developed by bigHead® Bonding Fasteners, a part of the Bossard Group, Lean Bonding allows users to bond fasteners to composite surfaces with incredible speed and strength, while also providing a solution that does not require drilling holes which can weaken the base composite material.

Lean Bonding allows fasteners to be permanently fixed to a suitable composite surface in as quickly as ten seconds! The process involves use of a bonding fastener equipped with a pre-applied adhesive, activated via rapid induction heating. After applying the fastener to the desired surface, the dry adhesive film rapidly cures, permanently securing the fastener.

Automated, semi-automated or manual installation methods are available, and cause no damage to the base material. Successful Lean Bonding is compatible with fiberglass, reinforced plastics, aluminum, steel and carbon fiber reinforced plastic. It is suitable for use with a variety of adhesives, fastener coatings, and sizes. Additionally, using a pre-applied adhesive ensures uniform adhesive thickness and repeatable bond quality. This makes it the ideal solution for the many technical challenges experienced when assembling composite materials that are not suited for clinching, riveting or welding.

Lean Bonding is a reliable process that offers excellent versatility for high and low production levels and can offer profound improvements in speed, quality, and cost.

Some Facts About Lean Bonding:

• The fastener has a 24mm head, comes in M5 and M6 sizes, and in 16 or 20mm lengths
• Wide range of OEM-approved finishes available
• Polyurethane and epoxy based adhesive options are available

Bossard is the industry leader in fastening products and solutions, and Lean Bonding is just one reason why global market leading manufacturing companies choose Bossard as their preferred and trusted supplier for innovative fastening technologies.

To learn more about Lean Bonding and Bossard’s other effective industrial processes, check out www.bossard.com or contact us at ProvenProductivity@bossard.com.

Laser cutting sheet metal has some serious benefits in time savings and accuracy. It can also cause some headaches when cutting holes for direct fastener assembly.

For many years, manufacturers alike have used thread forming screws with standard machine screw threads and case-hardened special points. These screws use pre-made holes, forming their own threads into the mating material. The thickness of the material generally dictates the size of the hole needed to create the lowest driving torque and highest stripping torque which leads to the best joint performance.

Drilling or punching into mild steel creates holes for these screws. Hole size recommendations exist for each size and thickness of the material. But, when laser cutting holes, we often see the heat affected zone, which makes the surface of the material around the hole somewhat harder. If using standard hole recommendations for drilling or punching, problems can occur during assembly.

Common Assembly Problems:

• Hard start – screws spin
• High drive torque – gun will not seat screws
• Breaking screws before seating

These problems usually show that the hole size is too small. With oversized holes, we often see threads stripping rather than achieving their assembly torque.

While it is difficult to provide recommended hole sizes for each material type, each thickness, and each method of preparation, performing a drive/strip torque test in a controlled environment may be the best way to ensure the best joint performance. Let’s look at an example of a test recently done by a Bossard engineer:

Plate steel provided by the customer with incrementally larger sizes of laser cut holes:

Graph of a typical test:

Graph of the average data for many hole sizes:

Typical summary data from one hole size:

By performing a joint analysis in our laboratory, we can recommend the proper hole size for your design to ensure optimal performance.

If you have interest in any type of joint analysis, check out Bossard’s latest Assembly Technology Expert services, especially the Expert Test Services pillar, or contact us at ProvenProductivity@bossard.com.

Doug Jones
Applications Engineer
djones@bossard.com

Your design has been in production for a while, and now it’s time to look into cost savings. Fasteners are such a small fraction of the total design cost, is it worth looking for savings in this area?

While it’s true that the cost of the fastener may be small, there are many hidden costs that are often overlooked when purchasing hardware. We call this Total Cost of Ownership, or TCO.

To better explain the TCO model in fastening, we use the iceberg model.

Total Cost of Fastener Ownership

On average, the fastener itself makes up only around 15% of the total costs. The remaining 85% of the costs come from development, procurement, testing, inventories, assembly, and logistics. This chain of events is adding costs to the entire fastening ecosystem.

Let’s look at an example from the Bossard Cost Savings Calculator.

If you have any interest in finding hidden cost savings in your design, check out Bossard’s latest Assembly Technology Expert services, or contact us at ProvenProductivity@bossard.com.

Doug Jones
Applications Engineer
djones@bossard.com

Not taking advantage of thread forming screws in your design? You may be missing out on some performance enhancements and cost savings! From plate steel and sheet metal to thermoplastics and aluminum, consider multifunctional fasteners for your next design.

What exactly are thread forming screws? Thread forming screws have the same basic thread pitch as a standard machine screw, with harder threads and different point geometry to create their own threads into an untapped hole. This eliminates tapped holes or nuts and locking features which may be necessary with conventional nut and bolt assemblies.

Self-Locking Effect

One of the big benefits of thread forming screws is the self-locking effect. Because they form their own threads, there are no gaps between male and female threads. This can lead to rotational loosening under vibration loads. This self-locking feature alone can be a good reason to switch.

Reduction of Fasteners

By eliminating nuts or costly tapping operations, as well as locking washers, adhesives or other locking elements, realizing cost savings over the entire joint is possible. Not to mention reducing the number of fasteners and operations needed for conventional assembly.

Specialty Thread Formers for Light Alloy Metals and Plastics

Many specialty type thread forms exist for assembly into light alloys such as magnesium or aluminum. They also exist for various thermoplastic materials. For some harder thermoplastics or thermoset plastics, adding a cutting feature can lessen the stress on the material. This will still create threads into the material eliminating tapping or costly threaded inserts.

For more details on thread forming screws, Bossard offers Expert Education seminars as webinars or in person at your facility, tailored to your specific questions and needs. Contact us at ProvenProductivity@bossard.com for more information.

Doug Jones
Applications Engineer
djones@bossard.com

Designing fastened joints begins with a good basic knowledge of fasteners. Many engineers think they know enough about fasteners to make good decisions, but what is your level of knowledge? Here is some good information with questions at the end to test your knowledge:

Drive Styles

What is the difference between the Philips drive and the Pozidrive?

• Applying too much torque to a Philips drive will cause it to “cam out” to avoid breaking the screw. This is beneficial for certain hand assemblies by consumers. For production assembly, it is not ideal due to tooling wear and operator fatigue if assembling by hand.

• Pozidrive has different geometry which transfers more torque into the screw with less downforce. In a production environment, whether by hand or automated assembly, tooling will last longer and achieving a specific torque without the drive slipping is possible.

How do you tell the difference?

Pozidriv has four “tick marks” on the face of the drive for identification.

Do they use the same driver?

Property Class/Grade

How do you determine the strength of a fastener by looking at the head?

The grade or property class marks are on the head.

• Left – property class 8.8 metric with the “8.8” stamped on the head
• Middle – three slash marks equally spaced is imperial grade 5, which is the same strength as metric property class 8.8
• Right – six slash marks equally spaced is imperial grade 8 which is stronger than grade 5

What does the triangle and the “ABCD” mean on the head? What does 8.8 stand for on the head of the metric fastener? What is the grade of fasteners below?

To check your answers to the questions above, contact us at ProvenProductivity@bossard.com to set-up a seminar at your facility, or keep your eyes open for our first webinar covering “The Anatomy of a Fastener”.

More than the basics, this seminar takes things to the next level by covering bolted joint principles and fastener manufacturing.

Doug Jones
Applications Engineer
djones@bossard.com

Often times when designing a bolted joint we try to use standard, off the shelf fasteners for the lowest cost, but the cost of the entire assembly is not considered. Take the example below found in an electric lamp:

Conventional Fastener Solution

Here we have three fasteners, a machine screw threading into a clinch nut, and incorporating an external tooth lock washer to create a good ground for a ring terminal. Seems like a pretty good, cost-efficient joint, right? But let’s look at another possible solution:

Multi-Functional Fastener Solution

This solution incorporates a multi-functional thread forming screw with nibs under the head to create our needed grounding contact. The screw itself is more than three times as expensive as the machine screw above. If we look at the total cost of the assembly, we can see the savings.

The multi-functional fastener solution results in a 60% cost reduction over the conventional solution.

Bossard offers Expert Education seminars as webinars or in person at your facility, tailored to your specific questions and needs. For a full seminar on Cost Efficient Assembly, contact us at ProvenProductivity@bossard.com.

What is the key to getting your fastened joints tight and keeping them tight? This is one of the biggest headaches that engineers face today. But with a little education and understanding of the bolted joint, the problem becomes easier to tackle.

Bolts Act Like a Spring

Believe it or not, we want bolts to stretch when we tighten them. By stretching bolts up to, but not beyond their yield strength, they act like a spring. This creates the desired tension in the joint to prevent clamped members from slipping and putting a shear load on the bolt. Bolts are only about 60% as strong in shear as they are in the axial direction, so avoiding this sideloading is key to designing good joints.

How long should your spring be for optimal joint retention? A clamping range of five times the diameter of the bolt is ideal if tightened. For example, an M10 bolt should have fifty millimeters of distance between the head and the nut when tightened to perform at its very best. Junkers vibration testing has proven this to be the best combination to avoid rotational loosening.

What about joint settling? Knowing the surface pressure of the material you are bolting together, compared to the surface pressure of the fastener is key. With the wrong combination, you can get joint settling and loss of clamp load which can lead to fatigue failure.

For more information on how to create secure joints, Bossard offers Expert Education seminars, both as webinars or in person at your own facility, tailored to your specific questions and needs. Contact us at ProvenProductivity@bossard.com for more information.