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Thread: Hacking Vs. Non-hacking RAF

  1. #1
    Member Number4's Avatar
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    Nov 2011
    Hong Kong

    Default Hacking Vs. Non-hacking RAF

    Anyone know why some RAF watches hack and others don't? I know they all conform to different Def-Stan specs, but what I can't figure out is what purpose it would serve having a non-hack watch. Some models that don't hack seem like they definitely should. For example, the Omega 53, Smiths Deluxe, and Hamilton 6B 9101000 all don't hack, and fall under DEF-3-A. Were these issued to pilots, and not navigators? These were all issued between '53 and '66 if I'm not mistaken, but before '53 you have the Mk11's which definitely hack, as well as the 6B/234s which were hacking, so why would they produce pilots watches without this function if they were already working it into most models?

    The other day I went to set my Omega 53 and thought the hack function was broken, because I always just assumed it hacked! When I realized it didn't, it just didn't make sense to me.


  2. #2


    I couldn't agree more. I'm hacked off for a second time.

  3. #3


    I can't speak for the Omegas or orders to DEF standards, but the hack-set (stop balance) on Smiths W10 have been known to break... and it is not unknown for military movements to have been replaced by near identical civilian non-stop balance movements.... but then many late civilian Smiths Astrals had military movements I suspect to use up parts before all production ceased. It's wise to check before you buy! RAF W10s should have stop balance fitted... in theory!

  4. #4
    Senior Member isologue's Avatar
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    Jun 2009


    I think Ken Gordon's article 'Zulu Time' touches upon this - well worth the read anyway. Apparently the 6B/542 watch was produced in response to an urgent request in 1951 for a few thousand more 6B/159s (which of course didn't hack). The introduction of the hack requirement with DEF STAN 3B was a refinement to the GS spec in response to GS operational needs. Remember too that the Mark 11 was designed specifically for astronavigation purposes (which were superseded before long) and the only 6B/234 that hacked was the ex-A-11 version that was so designed to meet USAAC/USAAF requirements. (I also believe that the A-11s were supplied to the RAF after WWII, and just happened to be black dialled hacking watches like the 6B/346s, although not as capable in their performance). The 6B/542 was of course waterproof and anti-magnetic - attributes obviously considered to be more desirable than a hacking function.


    Martin (isologue)

  5. #5


    The devil is in the detail!

    DEF-3 and -3-A - Wrist Watch, General Purpose, marked 6645-99-910-1000 (Omega 53, Smiths Deluxe & Hamilton 6B/9101000) were intended for "Quote" wrist watches for general service purposes in H.M. Armed Forces "Unquote".
    There is no suggestion they were meant for pilots. They were not required to hack and accuracy was a daily rate of 40 secs.

    DEF-3-B and Def Stan 66-4(Part 4) - Watches, Watch, Wrist, General Purpose, marked 6645-99-961-4065 (Smiths 6B & W10, Hamilton 6B/961-4065 & Hamilton 1971 0552/961-4065) were intended for "Quote" wrist watches for general service purposes in H.M. Armed Forces "Unquote". There is no suggestion they were meant for pilots. They were required to hack and accuracy was a daily rate of 40 secs.

    Mechanical navigators' watches on the other hand were required to hack and have an accuracy of 15 seconds daily rate of better (Mk XI, 6B/346 and 6645-99-521-1430 - No record of having been issued BTW).

    The 1980 CWC Quartz Date model became the issued Navigators' watch from 1980 onwards and surprisingly seemed to issued to RN ships navigators as 'Happy Jack' will attest.

    I would imagine that pilots in the 60's would be wearing Lemania chronographs and in the 70s' Lemania or Fab Four chronographs, which were required to have an accuracy daily rate of 30 seconds or better with chronograph functions.


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