My daughter has asked me to change the lock on her front door and, after learning about the subject on the internet, I had a look to make sure I ordered the right size lock. The fixing screw in the cylinder is not the bog-standard countersunk machine screw. It is hidden below a hole in the edge of the door. What appears to be an Allen key grub screw (difficult to see through the small hole) is hidden except when the handle is in the down (opening) position, when a brass "lever" moves out of the way.
I cannot get an Allen key to fit (I'll try to buy a selection of Allen keys tomorrow) but even if I could, I'm worried about how far out I should unscrew this grub screw - I don't want it to come out of its housing and fall down inside the uPVC door section.
The metal locking mechanism that goes up the edge of the door is marked YALE and the Euro Cylinder is marked ERA.
Has anybody ever worked on a door mechanism with this hidden grub screw arrangement? How long is the grub screw? Is there a real danger of it falling down the inside of the uPVC door stile? Where can I find information about this arrangement?
Thanks
CVB