Toggle latches, also referred to as over centre latches or over centre fasteners, are a mechanical device used to secure two panels or objects together. The panels or co planar objects are secured when the toggle latch’s loop is hooked onto a catch plate (hook) and the handle clamped down past the over centre position. The tension is released when the toggle latch’s handle is pulled up to the vertical position
Toggle latches are simple to operate and enable quick securing and release of 2 panels / objects.
There are many different styles or types of toggle latches including rigid claw, spring claw, flexible and under centre to name a few. The different types are designed to accommodate different application; however, this article will focus on one of the most common types used, the adjustable toggle latch (or adjustable over centre latch).
The different parts of an adjustable toggle latch
Adjustable toggle latches include a threaded latch arm that can be rotated to adjust the arm’s length to enable the right tension to be achieved.
For adjustable toggle latches the amount of force required to achieve the over centre position (overcome the cam) can be varied by adjusting the length of the latch’s arm. The shorter the length of the arm the more force will be required. The handle usually provides sufficient leverage to deliver the required force to achieve the over centre position. The greater the force required the less likely the latch can accidently release dues to vibrations or movement, once secured.
Toggle latches consist of the following components:
- Handle: The longer the handle the more leverage you will have to secure the latch into the over centre position.
- Screw Arm & loop: The length of the screw arm may be adjusted to vary the amount of force required to secure and release the latch. The loop is what engages with the hook or catch plate and comes in different shaped designs such as oval, triangular & as a T-Bar.
- Friction ring (on some models): Ensures that the screw arm remains in its original position and doesn’t accidently rotate, adjusting the arm length.
- Catch plate / hook: Is usually sold as a separate accessory, the toggle latch’s loop is hooked onto a catch plate (hook). The catch plate or hook is attached to the 2nd panel or object.
- Safety Catch: Some models of toggle latches come with a safety catch that can be engaged when the latch has been secured in the over centre position. This acts as a safeguard against the toggle latch accidently decoupling. This can be very important for some applications where the latch failure could result in a dangerous situation or significant equipment loss or damage.
- Padlock Hole: (on some models) This can be used to apply a padlock if security is important or a sealing pin to prevent the latch accidently de-coupling.
Adjustable toggle latches come in many different designs and sizes and are used in a wide range of applications such as ute and vehicle bodies, pop top caravans & campers, transport & storage cases, toolboxes, electronic & machinery enclosures, and many other industrial applications.
How do I select the right toggle latch for me?
In determining what size latch, you should use, the most important criteria is ensuring the strength of the toggle fastener is adequate for the maximum load it will be required to support. Well-made, high-quality toggle latches will generally come with a maximum load rating or ultimate tensile strength (UTS). As a rule of thumb, it is suggested to use a safe working load that’s half the UTS. The catch plate strength should also equal or exceed that of the latch and the method of securing the toggle latch & catch plate provide sufficient strength to meet the anticipated maximum loads.
Based on their strength rating, toggle latches can be divided into 4 broad categories:
- Light duty: This version is designed for objects like cabinets and boxes that are not frequently subjected to severe vibration, force, or unintentional opening. Since they are light-duty items, these toggle latches are more affordable and easier to use. In terms of sizes, they are also relatively smaller than the other types.
- Medium duty: These toggle latches were made to support a maximum load between 125 kg to 750 kg and are less likely to accidentally open due to vibrations and other causes. These are often used on toolboxes, transport cases and some industrial cabinets.
- Heavy duty: These toggle latches are made to support maximum loads between 1,000 kg to 2,500 kg. These toggle latches are often found on vehicle bodies, engine and industrial machinery covers, large transport containers / crates.
- Super heavy-duty: There are some applications that require super heavy-duty toggle latches, such as ute trailers and motor bodies. For these applications, safety is paramount, and the failure of a latch could have catastrophic results. These latches can have rated strengths greater than 7000 kg.
When you have selected the correct size latch based on the load requirements, other considerations when choosing the right toggle latch for you, might include;
- The available ‘real estate’ space for installing the latch and catch plate.
- Can the toggle latch (lockable over centre latch) be locked. This can be important if you want to ensure the latch can’t accidently open due to vibration or to prevent non authorised access. Alternatively, some toggle latches include a top mounted or side action safety catch, which also prevents accidental opening of the latch. The Snapflat latch prevents this with the inclusion of springs with the latch, which ensure the latch always stays engaged, even when the over centre position has been lost. The beauty of this design is that it doesn’t rely on the human operator remembering to engage the safety catch. These features are usually only found on the medium to larger size toggle latches.
- For some applications damage can be sustained to the toggle latches when not engaged as the latch handle and arm flap around loose and can even result in injuries due to people gauging themselves against a protruding latch. The Snapflat latch prevents this with the inclusion of springs with the latch, which ensure the latch when not engaged, remains flat and secured against the latch’s base.
- Manufacturing quality and material used. For some applications cheap and cheerful is adequate but for others where failure of the latch could result in equipment loss or damage and even injuries, then selecting a well-made latch that has been manufactured using high quality materials can be important. Toggle latches made from mild steel of zinc coated steel are generally not as strong as a comparable stainless steel over centre latch and will be more prone to corrode. The maximum load rating or UTS of a latch is a good guide as to the quality of the latch.
- Cosmetic appearances can be important for some users and applications.
Taking care of your toggle latches
Your toggle latch’s efficacy could be negated if adequate care is not taken. You can ensure their long-term reliability by:
- Correct installation to the surface, with adequate strength fittings to secure the toggle latch.
- Initial inspection of lock to check if all parts are functioning well.
- Ensure you have chosen the right toggle latch in terms of function and load
- Takes steps to minimise corrosion (i.e. keep lubricated, clean)