How The Master ML System Operates


Original Master lock cylinders can be easily repinned by turning the plug 180 degrees, then removing the old pins through existing holes drilled in the bottom of the cylinder housing. ML cylinder housings also have drilled holes, but the ball bearings are locked into the key dimples, preventing keys from being removed or inserted while the plug is turned. The solution is to remove the plug from the housing whenever cylinder servicing is required. An easily removable 'C' clip retains the lock plug in the housing. Master Lock makes a special follower which simplifies plug removal.

Ball bearings can cause a problem during repinning. There are four small ball bearings, two on each side. When removing the plug from the housing, always keep a finger on each side of the plug to hold the bearings in place as the plug is removed. A technician at Master Lock was consulted and agreed that putting a small dab of Vaseline on the ball bearings during reassembly was acceptable. This will serve to hold the ball bearings in place while re-inserting the lock plug into the housing. If a bearing gets misplaced, extra bearings are included in the ML #291 keying kit or a common 3/32" ball bearing can be substituted.

Large master key systems can also be generated. Tolerances of ML cylinders are reportedly tight enough to allow Master Lock to use single-step progression for master keying even though the increment between cuts is just .0155". The only stipulation is that no '1' master pins are used. These pin tumblers are rather thin and may catch in the rounded grooves milled into the sidewalls of the housing as the key is turned. According to Master Lock, a potential of 40,000 change keys could be generated for a single master key system. The maximum adjacent cut (MAC) is 6.

The available CK number choices are:

MK- CK cuts

0- 234567

1- 34567

2- 04567

3- 01567

4- 01267

5- 01237

6- 01234

7- 012345

Spool-shaped drivers are used in all but one chamber which does help to deter picking, but Master Lock stresses key control as the most important element of the ML design. While ML customers may have the same basic key blank, they will have key control due to differences in positioning of the dimple cuts.

One question brought up at a Master Lock ML training seminar centered on the possibility that a locksmith could drill extra dimple cuts on an ML blank in order to operate ball bearings in another virtual keyway. The instructor answered that each Level 2 and Level 3 key blank is marked with a specific ID code number which is traceable to the dealer who ordered the ML key blanks. If a double-drilled ML key is discovered, the locksmith company or commercial account that was assigned that ID number will be immediately removed from the program by Master Lock.

ML System lock cylinders may be ordered in a four-pin version as part of the laminated padlock line or in a six-pin version for all Master ProSeries padlocks. Individual ML cylinders can be ordered using a 'UN' designation which means they will be pinned with all '0' depths but will not be supplied with keys. The ML System is available as a commercial product only sold through the locksmith and industrial distributor.

For more information, contact your local locksmith distributor or:
Master Lock Company
Tel: 414-571-5625