The Medeco Classic came out around 1970 or so and remains a very hard lock to pick. It uses chisel point pins that can be rotated 20 degrees by angled cuts on the key. Proper rotation of the pins allows a sidebar to retract and if the pins are also at the proper shearline, the lock can be opened. There are several tools that a lock picker can use to help rotate the pins in the Classic, the Medecoder, groove grabbers and some others. Several expert pickers have demonstrated their ability to rotate the pins with an ordinary pick.
The Biaxial came out about 1985 and is very similar to the Classic. The big difference is that the chisel point on the pins is not on center, rather it is before or after the center and the pins are called Fore or Aft. The Biaxial gave Medeco another 20 years of key patent protection and allowed for a large number of bitting differs. This allowed Medeco to do some very complex master keying, and it would seem to be higher security. However these locks are susceptible to code setting and bumping with properly cut keys. They are also susceptible to groove grabbing tools like the Classic lock.
The M3 came out around 2003 and is essentially a Biaxial lock with the addition of a slider. The slider sits at the front of the sidebar and prevents the sidebar from retracting. The key has a special shoulder that moves the slider and this gained Medeco another 20 years of key patent protection. The patent on the M3 key expires in 2021. The slider can be easily bypassed with a bent paper clip and the lock offers no more security than a Biaxial. They can also be bumped or code-set and then picked.
The Bilevel is a low security lock that takes the same key as the M3. It is designed to be a cheaper lower security lock that is integrated into an M3 system. Medeco suggests it be used on closets and lunch rooms. It can be bumped and picked.
In 2005 Marc Weber Tobias began looking very seriously at Medeco locks. He along with several others discovered a number of flaws in the design that they were able to exploit to create bumpkeys and code setting keys. They give the details of their efforts in the book “OPEN IN 30 SECONDS”. Great read for anyone interested in Medeco locks. Tobias also discovered a few destructive entry methods for Medeco locks. Some are VERY simple and use easily available tools. We won’t talk about those methods here. However, Medeco locks are not as secure as some people believe.
In an effort to remove several vulnerabilities, Medeco introduced ARX pins to prevent groove grabbing and they allowed some additional pin rotation angle combinations. The ARX (Attack Resistance Extended) pins feature a sidebar slot that is milled into the side of the pin and does not extend all the way to the chisel point. There is nothing for the groove grabber to hook into, so it can’t be used to rotate the pins. The ARX pins are supposedly put in only at the request of the customer, or for high security applications.
The additional rotation angle combinations are included in the generation 3 code book and these locks require 16 code setting or bumpkeys rather than the 4 keys required for the generation 2 locks.
To use the code setting keys, you should determine if the pins in position one and two are fore or aft. Doing this can reduce the number of keys you need to try to open the lock. There are several ways to probe the pins and see if they are fore or aft, and then refer to a table and choose your code setting key or keys. Put the code setting key in the lock and wiggle it a bit so that the pins are seated in the cuts. Put a slight amount of tension on the lock with a suitable tension tool and the sidebar will set. Hold the tension and withdraw the key, then pick the lock as you would pick any normal lock. That’s it. Be aware that there will be a couple of mushroom or other security pins, and that Medeco locks are sometimes very hard to pick even without the sidebar.
Interesting to note that once the pins are rotated to the proper angle, the tension can be released and the pins won’t rotate unless they are physically disturbed by a pick or other tool. Also, these code setting keys are made to work on the Biaxial and M3 locks, not the Classic. In this respect the Classic actually has higher security than the M3.
After I made these keys, I tried one of the bumpkeys in a six pin Biaxial. It took me about six hits before the lock popped open. I’m no expert in bumping, I think this might be the third time I ever bumped a lock open. If anyone wants to know the cuts I can give you a chart for the 4 keys or the 16. I’m not sure if I should post the charts in the open.
>> Edit. I can't find the original pictures. The pictures above should be pretty close. <<