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Hole Size Matters!

Daddy to the rescue, the savior of broken toys! Well, that’s what my initial thought was before I had to go buy my daughter a new toy because I chose the wrong screw to replace the unusable one. My daughter’s favorite toy would always come loose from the plastic joint due to the repeated fix and the wear and tear from a 6-year-old. Who would have known there is an art in fastening plastic joints with a screw? Did you know the size of your pilot hole, in relation to the diameter of the boss is important? Too large of a hole will not have enough thread engagement, and too small of a hole will cause stress fractures to the boss. The material of boss will have an effect on the size of the pilot hole to have proper seating of the screw. There are also advantages of choosing the right screw for the job. You want to have a screw that has low driving torque and high stripping torque. Having great vibration resistance, especially when dealing with 6-year-old playing habits is very important. Click here to find the right screw to fit the hole.

What will it take for you to be the hero again and be the super parent that you are? That’s right, hole recognition and proper design. The experts at Bossard can help you design and choose the right hole sizes for the easy fix. Saving one toy at a time is what you do best! Contact us at ProvenProductivity@bossard.com with any questions.

 

John Syharath
Technical Sales
jsyharath@bossard.com

July 21, 2017
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Fastener Materials

Fasteners come in a variety of materials.  The choice of materials will be decided by the application and environment.  The most popular material options are steel and stainless steel. Other options include alloys based on aluminum, copper, titanium, nickel, cobalt and plastics. Important parameters that will help choose the right material are spelled out in the table below.

Parameters

Application examples

Mechanical
(strength, ductility, toughness, fatigue)

Steel fasteners come in several grades – make sure that all static and dynamic loads are identified when choosing the right strength.

Corrosion resistance
(galvanic corrosion and stress corrosion cracking)

Several stainless steels and other nickel, cobalt and titanium based alloys have very good corrosion resistance properties.

Beware of galvanic corrosion when designing with different metals!

Temperature resistance
(high temperature oxidation and creep)

Nickel based alloys are used where high corrosion and heat resistance is needed.

e.g., aircraft and land-based gas turbine engines.

Magnetic permeability

Some stainless steels can be obtained with a very low magnetic permeability which is required in applications like magnetic resonance imaging (MRI) scanners.

Weight saving

Some titanium grades show a 40% weight saving compared to steel with equal strength.

e.g., automotive applications.

 

For more information on fastener materials, contact us at ProvenProductivity@bossard.com.

 

Fadi Saliby
Technical Sales Director
FSaliby@bossard.com

July 14, 2017
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Loose Fasteners: Causes and Solutions

A common headache for engineers and consumers alike is fasteners coming loose and causing problems. So, what are some of the causes of loosening?

Under tightening, which results in low clamp load, is one main cause of loosening fasteners. If a joint does not have enough clamp load to keep the joined parts from slipping against one another, rotational loosening or fatigue failure may occur. It’s important to follow manufacturer’s recommendations for proper tightening.

Using fasteners with a small bearing surface area to join softer materials can lead to embedment of the head into the material. Over time this can cause a loss in clamp load resulting in loose joints. It’s important to understand surface pressure limits of screws and mating materials, and match them accordingly to avoid embedment. Flanged head fasteners or hardened washers are a good way to spread the load out and avoid this problem. It should be noted that many flat washers are not hard enough to support high-strength fastener loads, so choose your washers accordingly!

Vibration is another cause of loose fasteners. In a nut and bolt joint, a good design will actually stretch the bolt slightly to create a rubber band-like effect, which helps to keep the fastener tight. A good rule of thumb for design engineers is to use a clamping length of 5 times the bolt’s diameter to ensure good stretch when torqued properly. For joints subjected to vibration which cannot use this rule, then serrations, locking patches, or specialty lock washers may be needed.

For more information on how to keep fasteners tight, contact us at ProvenProductivity@bossard.com.

Doug Jones
Applications Engineer
djones@bossard.com

June 23, 2017
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