Whether you're dealing with an issue of grip, gravity, or geometry, working with an experienced hardware supplier can often expose you to a broader range of options for improving operating efficiency and cutting hardware or installation costs.

By Gerry Clisham, Southco, Product Management Leader

Every access hardware application has its own unique requirements and considerations. But even across multiple styles of latches and hinges, there are several common denominators that can affect physical performance and customer satisfaction. These include the grip requirements of your latch, the effects of gravity, and the geometry of your door, frame or enclosure design.

Grip

Always orient the rotating latch so that its cam falls into a latched position.

The grip dimension is the distance from the base of the latch (where it touches the face of the door) to the point of engagement (where the cam or pawl touches the frame or keeper). In general, latches come in three different grip styles.

• Fixed grip: The grip on these latches cannot be adjusted, therefore door/frame production tolerances must be consistent over the life of the application. Typical hardware in this category includes push-to-close latches, cam and compression latches, and quarter-turn fasteners.
• Adjustable Grip: To allow for manufacturing variations or changes in grip over the life of the applications, the grip on this hardware can be set in production or adjusted later in the product’s life. Typical products in this category are cam and compression latches and certain push-to-close latches.
• Self-Adjusting Grip: The grip for these latches is set by the user on each application. This allows the latch to accommodate changes in grip over the life of the application. Common products in this category are cam and compression latches, draw latches, and quick access fasteners.

When calculating the grip dimension and the corresponding latch, be sure to include allowances for any accessories that might come between the base of the latch and the door, such as washers, spacers, dust covers, or padlock accessories. In gasketed enclosure applications, include the compressed dimension of the gasket, which should be available from your gasket supplier.

Gravity

A simple consideration — especially for simple cam latches that do not have much friction between the cam and the frame or keeper — gravity is a variable not to be overlooked. Always orient the rotating latch so that its cam falls into a latched position. This can be accomplished by ordering a Type "A" (clockwise to latch) or Type "B" (counterclockwise to latch) unit.

When properly installed on a vertical door, a cam latch will be open in the 12-o’clock position and latched in either the 3-or 9-o’clock position. Therefore, gravity is always pulling the cam into the closed position.

Other hardware components that can be affected by gravity are hinges or position control devices used to pivot or hold doors or other equipment components in position including those with a horizontal orientation where the weight of the component wants to force it to close. For example, a position control hinge with an integral lift-assist device can actually help to lift a door or component, as well as to hold it in position. When encountering such applications, be prepared to work closely with your supplier to communicate the angles, dimensions, and forces involved in the application.

Geometry

The grip dimension is the distance from the base of the latch to the point of engagement.

The third G, geometry can also dictate the latch or hinge configuration you will need for an existing enclosure. Having the flexibility to control a new enclosure design and door/frame interface can create options for saving on both your purchasing and manufacturing costs for hardware and installation. Wherever possible, consider the variety of factors that can come into play to affect latch selection according to application geometry:

• Material thickness.
• Whether the latch will engage with the frame, an independently mounted keeper or a strike plate.
• The need for a gasketed enclosure.
• Whether panels are co-planar or not.
• The consistency or variability in the tolerances of a door or enclosure.
• Door length as it affects flexing.

While some latch and hinge styles do not tolerate variations in enclosure geometry, dimensions, or mounting locations, others offer flexibility to compensate for variances encountered in the assembly process or in the field. These include adjustable cam latches and compression latches that can be adjusted after assembly or in the field, as well as adjustable offset hinges that can be used to compensate for differences in gasket thickness.

Another consideration in the geometry of enclosure design and the selection of enclosure hardware is whether the application requires a flush front to the enclosure door – perhaps for space savings in close quarters, or to minimize obstructions in high-traffic areas. This can be accommodated with recessed latches, latches mounted on the side of the enclosure, in-line hinges or internally mounted hinges.