Magnetic Locks: Mechanical Locks with Magnet-Coded Keys

Not the Same as an Electromagnetic Lock or a Magstripe Card

Three different technologies are often called "magnetic." This page covers only the first.

• Magnetic keyed locks (this page). Permanent magnets in a key position tumblers in a mechanical cylinder or padlock. No power is involved.
• Electromagnetic locks, often called maglocks. A powered electromagnet holds a steel plate on the door. Lockwiki notes that "mechanical and electronic locks that use a magnetic component to secure a door strike are not typically classified as magnetic locks."
• Magnetic stripe and magnetic keycards. These are credentials read by an electronic or electromechanical lock. They are a separate category, covered under card readers and access control. One historical example, Schlage's CorKey magnetic keycard, appears in patent listings alongside magnetic keyed locks. It is a card system, not a magnetic keyed cylinder.

How Magnetic Keyed Locks Work

Designs vary. Lockwiki notes that many magnetic locks use cylinders whose parts must be brought to the shear line, as in a pin tumbler lock, while "others interact directly with the bolt."

Wikipedia describes the general principle. The key uses "from one to many small magnets oriented so that the North / South Poles would equate to a combination to push or pull the lock's internal tumblers." Because both attraction and repulsion are available, a magnet's orientation forms part of the code, not just its position. Wikipedia describes one hybrid form in which the key is cut like a normal key and also contains magnets. To open it, three things must be correct: the cuts, the magnet locations and the magnet poles.

A 1970 U.S. patent by Kiyoyasu Wake of Tokyo, US 3,518,855, sets out the same idea in patent language. Permanent magnets in the key move permanent magnets in the lock "by the action of attraction or repulsion force … depending upon the orientation of the polarity." The patent notes:

• the key "has smooth plain surfaces";
• with n magnet pieces the design offers "2^n different combinations of key changes";
• the magnetic tumblers can be combined with pin-, disc- or lever-tumbler mechanisms to increase the number of key changes.

Early Patents

Magnetic keys are not new. Lockwiki notes that "patents for magnetic locks stretch back to the 1800s."

One early example is U.S. Patent 428,247, "Magnetic Lock," granted May 20, 1890, to William W. Fenner of Kansas City, Missouri. In Fenner's design, pivoted tumblers of soft iron were normally out of line with openings in a barrier plate. The key was a horseshoe magnet that swung them into alignment. Fenner's stated goal was a key that could not simply be copied: "the mere duplication … of the shape or configuration of the key will not enable the lock to be operated."

An appendix list of magnetic lock patents compiled on LockpickingForensics.com shows how the idea kept returning:

Despite this, Lockwiki says magnetic locks "were not historically popular due to their low number of differs, expense in manufacturing, and relative difficulty in mass-producing small, powerful magnets." It adds that later advances produced a number of designs, "some of which are included in modern high security locks."

MIWA EC

One well-known example is the MIWA EC. Lockwiki describes it as using up to fourteen magnetic tumblers in two rows of seven on either side of the keyway, and calls it "one of the few locks with no visible locking components in the keyway." The key looks like an asymmetric dimple key with magnetic inserts.

MIWA's own Japanese-language product pages now list the EC cylinders, including the 76EC, as discontinued (廃止シリンダー). Lockwiki says the EC was superseded by the MIWA 3800.

Lockwiki ties the EC to US 3,518,855, and the LockpickingForensics list calls that patent "Early MIWA EC." Google Patents, however, lists half of the patent as assigned to Fuji Manufacturing Co., not MIWA. That association is not treated as settled here.

EVVA MCS

A current example comes from EVVA. The company says its Magnetic Code System (MCS) technology "was developed in 1979." EVVA's description of the cylinder:

• It contains "eight freely rotatable magnetic rotors" to the left and right of the key channel.
• Four magnetic pills in the key set those rotors.
• The magnets are made from samarium cobalt.
• The key combines "one magnetic and two mechanical codings."

In its brochure, EVVA describes itself as "the only manufacturer" producing this type of high-security magnetic system. That is a manufacturer claim and is attributed here, not stated as fact.

Security Notes

Wikipedia says magnetic-coded keys "cannot be reproduced by locksmiths by sight or other 'human sensed' information." It also notes the downside: a limited supply of blanks can make legitimate duplication "more difficult and more expensive." These are key control tradeoffs. Like all locks, magnetic locks are rated by product. See high-security locks, UL 437 and EN 1303. This article does not describe ways of opening magnetic locks without the key.

Related Topics

• Electromagnetic locks (maglocks)
• Card readers
• Access control
• Pin tumbler locks
• Dimple locks
• Key control
• High-security locks
• UL 437
• EN 1303

Sources