Anyone who is reasonably handy might assume that replacing the lock cylinder in their front door is something they can do themselves – perhaps because new keys are needed or for security reasons after a key has been lost. And if it looks as simple as in the following video, wanting to save the cost of calling a locksmith seems only natural.
Remove the screw, replace the lock cylinder and put the screw back in – unfortunately, it is not that simple with Biffar security locks. Removing the cylinder is still easy. But then it refuses to go back in: something suddenly blocks the cylinder from being reinserted. In my case it was a small brass plate that could not simply be pushed aside (see photo above). While searching online I found this carpentry forum. It reports that a special tool is required to install cylinders in Biffar security locks. Apparently this tool is called a “Zabadäus”, and supposedly only locksmiths authorised by Biffar have one.
However, forum user Michael SB writes:
You only need the Zapadäus if the door is closed and the cylinder is removed while the door is locked.
To find out how it works without the special tool, I removed and dismantled the entire mortise lock; see image 1 below. Image 2 shows the mechanism that prevents the lock cylinder from being inserted. The third image shows how to release the lockout mechanism with the housing open. Finally, image 4 shows the trick for reinserting a lock cylinder without Biffar’s special tool. You can use a bent Allen key, for example, to operate the bolt inside the installed mortise lock. While doing so, reinsert the lock cylinder. As it is pushed through, the cylinder can now move the brass plate down and out of the way. And just like that, you have saved yourself the locksmith call-out with the special tool.
UPDATE 27 April 2014
Reader Mario emailed me with the following information:
If the door can be opened and you have a clear view of the latch – which is normally the case because you have just removed the screw holding the lock cylinder – you release the safety mechanism by inserting a pointed tool (awl, nail) into the small hole below the latch. The locking pin becomes movable and can then be pushed down by the lock cylinder itself.
The hole is even visible in your image #4.
Best regards, and thanks for the helpful pictures
Thanks for your feedback, Mario!
