What type of shackle should I choose?

The shackle of your padlock is an obvious point of attack for thieves wielding bolt cutters, saws and similar tools. It’s therefore important to strike the right balance between reducing the amount of exposed shackle and allowing sufficient clearance for your purpose. As a starting point though, always choose a padlock that secures the shackle in two places within the lock body.

close padlock shackle

Close shackle

A close shackle padlock has built-in shoulders that enclose all but a small portion of the shackle and therefore minimize the risk of attack. Many insurance companies insist on the higher security of a close shackle lock.

The close shackle design however also reduces the usable clearance of the lock so it may not always be practical, for instance when securing two chain links together or used in combination with a shrouded hasp.

open padlock shackle

Open shackle

In open shackle padlocks the majority of the shackle is exposed. This makes it easier to pass through holes, links and around bars but it is much easier to attack.

 

Semi-enclosed shackle

A semi-enclosed shackle padlock is a compromise offering greater flexibility than a close shackle padlock and improved security over an open shackle model.

long padlock shackle

Long shackle

Many open shackle padlocks come in a choice of shackle lengths. While a longer shackle may be essential when the shackle needs to pass through multiple hasps or fittings, remember, the longer the shackle, the more vulnerable it will be to attack.

adjustable padlock shackle

Adjustable shackle

As the name suggests, the shackle length in adjustable shackle padlocks can be varied to suit your purpose.

 

What padlock shackle thickness and material do you need?

The diameter and material a padlock shackle is made from can have a big impact on security, weather and corrosion resistance and price.

Shackle thickness

In general, the thicker the padlock shackle the higher the security level – providing a suitable material is used. As a rough guide, high security shackles are a minimum of 10mm in diameter; medium security shackles are 7mm-9mm; and anything less than 7mm is considered low security. 

Materials

Padlock shackles come in a variety of materials, from metals to plastics, giving a wide range of options covering security, resistance to corrosion, weather-proofing and cost.

Molybdenum is the strongest, most reliable material used in padlocks and is highly resistant to corrosion. It is also the most expensive. Molybdenum has been proven in high-risk situations such as the nuclear, defense and space industries.

Boron is a high-grade precision steel that is often used in advanced automotive and heavy-duty industrial applications due to its extreme strength.

Solid steel and case-hardened steel are durable and cut-resistant materials. Solid steel and case-hardened steel padlocks are typically used in higher security applications and are often chrome or zinc-plated to resist corrosion.

Stainless steel is similar to solid steel in terms of durability and tamper resistance but stands up better to the elements. 

Brass is more durable than plastic but not as tamper resistant as steel. Brass padlocks are an inexpensive option when a weather-resistant light security lock is needed.

Plastic padlocks are typically used in a light security situations where tampering is unlikely.

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