by Bump » 22 Dec 2006 12:44
Column 1: Lever number.
Column 2: Lift height - the height the lever needs to be lifted to align gate and stump. Ignore for the moment although this information is useful when you come to mix up the pins (you will) as they usually correspond to the length of the pin.
Column 3: The measurement of the impression gained from the lever bellies after taking an impression with a "P" key in the "LOCK" direction.
Cover the "P" key with plastercine (not play do) sufficiently to take the impression, but without smudging it on the lock body, and measure up from the intersection of the key stem and blade using a micrometer. Compare the measurement with the chart to determine which lever it is.
The Invinvible levers are arranged ABACD, ie Levers 1 to 5 from the bolt are arranged so that lever 1 is always the same as lever 3 (eg:53524) Once you have calculated all 5 levers, configure the pins and make-up key.
Notice there is room for 7 pins, depending on which side of the lock you are operating from place any of the longer pins to fill the spaces and act as curtain turners. I prefer to mirror the active pins ie a 53524 configuration would be pins 4253524, this is so I can use the key from both sides or cut a duplicate if needed.
This type of decoder relies on accurate measurement and the careful alignment of the pins in the make-up key. Sometimes, even with the corect combination, its necessary to jiggle the make-up key to get the lock to open.
If you dont have "P" keys, SV will supply them.
A simple chart for keeping track of your measurements:
5 4 3 2 1
A B A C D
5 3 5 2 4
4 4 1 3
Sometimes you might feel that the measurement could be one of two possible levers, write them both down so you can swap the pins out to the next possible pin.
As you havent submitted your location I am assuming you have some knowledge of mortice lever locks and this explanation is filling in the blanks.
