Time to dig out some of my DEC XX2247 keys

Fred Cisin cisin at xenosoft.com
Wed Jul 15 20:49:06 CDT 2015

Wow! should I dig out my Herty-Gerty?

> On 16/07/2015 00:13, Jay Jaeger wrote:
>> One size fits very many, but not all.  I know for sure that the PDP-8/L,
>> PDP-8/m, PDP-12, PDP-11/20, PDP-11/40, PDP-11/45 and VAX-11/780 all use
>> the same xx2247 key.  My PDP-11/24 has a silly plastic "anti static"
>> key, but the xx2247 works there, too.  But my PDP-11/05 and GT40 use a
>> different kind of more "normal looking" key.

On Thu, 16 Jul 2015, Pete Turnbull wrote:
> To the best of my knowledge, there are only three keys: the tubular XX2247 
> which is used on most -8s and -11s including my 8/es and 11/34, the one that 
> looks like a filing cabinet key used on just a few machines (all keyed 
> alike), and the plastic "key" used on later Vaxen as well as the 11/24 - 
> albeit in a variety of colours of plastic.

We had a similar discussion four years ago.

To oversimplify slightly,
XX2247 is a very ordinary "ACE" lock/key from Chicago Lock Company.
"XX2247" is not the depths of the cuts of the key.  Instead, it is
an "index" into the code.
If you have access to the right "code book", you look that up and it gives 
you a sequence of key cut depths, expressed as numbers.  If you DON'T have 
the right code-book, then you can measure the depths of the cuts.
Thus, if you look up "XX2247", you get: 5 1 7 3 7 5 7
If you have ACE compatible key cutter, then you set those numbers for the 
cuts.  If you don't have a suitable cutter, then you can look up what the 
physical measurement is for each of those numeric cut names (provided 
below) and then use a small end-mill in a drill press.

Four years ago, Ethan Dicks, who is quite familiar with the XX2247 key 
looked up the appropriate numbers in response to some speculation:

>> Here's what I got from two original XX2247 keys...
>> The cut depths, clockwise from the first position, looking into the 
>> end with the key at the "twelve 0'clock" position are:
>> Key 1      Key 1      Key 2      Key 2
>> 0.0770"     1.94mm     0.0785"     1.95mm
>> 0.0150"     0.37mm     0.0155"     0.39mm
>> 0.1055"     2.68mm     0.1070"     2.72mm
>> 0.0435"     1.13mm     0.0455"     1.13mm
>> 0.1075"     2.72mm     0.1085"     2.74mm
>> 0.0780"     1.96mm     0.0785"     1.98mm
>> 0.1075"     2.72mm     0.1095"     2.77mm
>> I'm not quite sure what this says about cutting tolerances or what 
>> the depths of cut are.

On Mon, 25 Apr 2011, Ethan Dicks wrote:
> Not sure about tolerances (my brother is a locksmith but I'm not), but
> according to...
> The depths by number are:
> 1 - 0.0155"
> 2 - 0.0310"
> 3 - 0.0465"
> 4 - 0.0620"
> 5 - 0.0775"
> 6 - 0.093"
> 7 - 0.1085"
> 8 - 0.1240"
> Meaning that the XX2247 key would have depths (in the order you
> describe) of 5-1-7-3-7-5-7
> A locksmith set up for ACE cutting would have the code book to convert
> the serial number into the depth sequence, so the number on the key is
> the important datum.  Knowing the numeric depths is handy when you are
> pinning a lock so you know which bin to pull pins from.
> -ethan

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