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Project help - please measure your NATO Mersey key for me

PostPosted: Wed Mar 11, 2020 2:27 am
by MHM
My new project is to learn as much as I can about this iconic lock.

At the moment I'm interested in its key, and specifically I'm looking at the variations in key bitting lengths and figuring out both the bitting steps, and the manufacturing tolerances. If you have a Mersey key in your collection, could you please measure the shaft diameter, and the lengths of each cut including the shaft, as per the picture below?

Other data I'm interested in is whether your key is a makeup (like mine in the photo below) or solid, and anything you think is interesting or unusual about your key. Is it handcut? Are there unusual wear patterns? Whatever. A photo would be great.

Nomenclature:

Depending on whether you have the 10 or 14 lever version, you'll have two unopposed cuts the same length on one side of the key at the bow end (these tension the bolt and on my key are smack on 13.00mm) and then either 5 or 7 paired cuts. We'll call this the LEFT side. So L1 will be the first cut immediately after the two tensioning cuts, R1 will be the opposite, and so on. Measurements in mm would be appreciated and for the love of God make sure your calipers are zeroed...

Also: I'm in the market for both Mersey locks (with or without keys) and Mersey keys by themselves. Any version, any condition. Swaps, cash, whatever.

Thanks and best wishes,

Michael.

Re: Project help - please measure your NATO Mersey key for m

PostPosted: Thu Mar 12, 2020 5:04 pm
by safecracker33
You will find that you have slightly different step heights for the 10 lever versions as the lever designs and step heights changed (only slightly) from 1976 onwards, the 14 lever I think came in in 1989

Re: Project help - please measure your NATO Mersey key for m

PostPosted: Tue Mar 17, 2020 12:52 pm
by MartinHewitt
14 lever with solid brass key from 1990.

Left V: 11.6, 11.7, 12.5, 12.9
Right V: 10.3, 10.9, 11.7, 12.0, 12.5

Re: Project help - please measure your NATO Mersey key for m

PostPosted: Tue Mar 17, 2020 2:35 pm
by MHM
That's fantastic, thanks. That looks like the cut heights are spaced by 0.4 +/- 0.1 on each side. Which of those figures is the double-thickness cut to throw the bolt?

Re: Project help - please measure your NATO Mersey key for m

PostPosted: Tue Mar 17, 2020 3:11 pm
by MartinHewitt
Actually none. The bolt throwing part is 13.5.

Re: Project help - please measure your NATO Mersey key for m

PostPosted: Tue Mar 17, 2020 3:54 pm
by MHM
Brilliant, thanks very much. The guys who designed these locks have created a truly beautiful device.