The NF3 is a pin-tumbler lock made by Nemef. Compared to the NF2, it contains more anti-drill protection elements (SKG3), unauthorized key copying prevention in the form of the security card and finally there is a "hidden warding" element.
Principles of operation
- See also: Pin-Tumbler (Principles of Operation)
The lock contains six pin stacks. Its most distinctive feature is the use of multiple diameter keypins, which together with a special warding causes the key pin tips at rest aren't at the same level (sometimes referred to as "shadow drilling"). These features provide additional resistance to key bumping attacks. The pin stacks alternate between serrated and spooled drivers, but due to the way the key pins rest in the chambers, the spools effectively engage only when paired with three shortest key pins. All of the drivers have slightly tapered tips, which gives this lock its bad reputation among the locksport community.
The warding is not very restrictive and the keyway itself is not paracentric. There is a passive pin inserted into the core, although there is no corresponding groove in the bible, which means the pin serves only as a "hidden warding". Looking at the left side of the key, there is visible groove, with which the pin interacts. Interestingly enough, there is an anti-drilling element just behind this passive pin.
To disassemble a double euro cylinder, use of a pinning shoe is the preferred method.
Other possibility is to use a segmented follower, but that requires that both cores are pulled out a bit to allow a cam removal. Then a core should be rotated to approximately 4:30 or 7:30 o'clock position (135 degrees either clockwise or anti-clockwise) to prevent driver entering a gaps for the cam clutch. Then a segmented follower can be used to remove the core.
When assembling the lock, take care to insert the cam clutch oriented correctly (see the notch on the top of the key blade), otherwise it would be impossible to fully insert the key into the lock.
The Nemef NF3 is vulnerable to one or more of the following:
- Key bumping (It is resistant to but theoretically possible to bump this lock)