Typically, bank vault combination locks break as a result of daily use. These locks are precision mechanisms that should receive yearly maintenance–especially lubrication to minimize the effects of metal-on-metal contact between internal components. In the real world, these locks usually get attention only when they fail. “Bankers aren’t big on preventive maintenance,” said Daniel Graffeo, president of TMI Lock Inc., a supplier of these specialized locks.
To keep TMI’s vault locks in working order, even when they don’t get the recommended upkeep, Graffeo made some changes in the lock materials and preferred lubricant. He estimates that locks whose moving components are made from die-cast zinc alloys and lubricated with lithium grease need maintenance every six to 12 months. TMI supplies vault locks that have operated maintenance-free for more than seven years without failure. The key to their longevity is internal bearing surfaces made from phosphor bronze and lubricated with Magnalube-G PTFE grease.
Bank vault lock designs have traditionally used zinc die-cast alloys for all the internal components. Die-cast zinc is cost effective, readily available, and has a long history as the material of choice for locks. The problem, however, is the wear and grinding that results when all-zinc components come in contact with one another.
Magnalube-G features a proprietary formulation: it suspends PTFE lubricating particles in high-quality base oils and uses non-soap elastomeric thickeners. Because it has no soap base, Magnalube-G stopped the in-situ creation of a “grinding compound” that occurs with lithium grease. It also provides all the benefits of PTFE lubrication without any of the consistency problems associated with solid lubricants.
According to Graffeo, Magnalube’s PTFE component forms a thin persistent film on the surface of the lock components. “Even with all its oil gone, Magnalube maintains 35 to 45% of its lubricity,” said Graffeo.