Tubular pin tumbler lock

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The key pins (red) and driver pins (blue) are pushed towards the front of the lock, preventing the plug (yellow) from rotating. The tubular key has several half-cylinder indentations which align with the pins.
The protrusion on top of the key fits into the rectangular recess in the lock, causing the indentations to properly align with the pins. When the key is inserted, the gaps between the key pins (red) and driver pins (blue) align with the shear plane separating the plug (yellow) from the outer casing (green).
With the pins correctly aligned, the lock may turn.

A tubular pin tumbler lock, also known as Ace lock, circle pin tumbler lock, or radial lock, is a variety of pin tumbler lock in which 6 to 8 pins are arranged in a circular pattern, and the corresponding key is tubular or cylindrical in shape.

Tubular locks are commonly seen on bicycle locks, computer locks, elevators, and a variety of coin-operated devices such as vending machines,and coin-operated washing machines.


Tubular pin tumbler locks are generally considered by the general public to be safer and more resistant to picking than standard locks. This is primarily because they are often seen on coin boxes for vending machines and coin operated machines, such as used in a Laundromat. However, the primary reason the locks are used in these applications is their lack of the depth requirement that most other locks require.[1] ,

There are several ways to open them without a key. Even though the pins are exposed, making them superficially easier to pick, they are designed so that after all pins are manipulated to their shear line, once the plug is rotated 16 to 18 around, the pins will fall into the next pin's hole, requiring re-picking to continue. As such, picking the lock without using a device to hold its pins in place once they reach their shear line requires one complete pick per pin.

Such locks can be picked by a special tubular lock pick with a minimum of effort in very little time; it is also possible to defeat them by drilling with a hole saw drill bit. Standard tubular lock drill bit sizes are 0.375 in (9.5 mm) diameter and 0.394 in (10.0 mm) diameter.[2] To prevent drilling, many tubular locks have a middle pin made of hardened steel, or contain a ball bearing in the middle pin.

In 2004, videos circulating on the Internet demonstrated that some tubular pin tumbler locks could be easily opened with the shaft of an inexpensive ballpoint pen of matching diameter. One website revealed that the weaknesses of the tubular pin tumbler mechanism had first been described in 1992. (see Kryptonite lock).


  1. ^ "A Beginner’s Guide to Tubular Lock Picking". 
  2. ^ "Tubular Lock Saws". hpcworld. HPC. Archived from the original on 28 September 2011.