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  1. #11
    Join Date
    Dec 2009
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    1,485
    Country: United States

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    The warding plug looks like it's "pot metal" (zinc alloy) so it was probably cast. Machining/broaching a spiral seems unlikely.

    Here's an image of a much tighter twist. I don't have this lock, the image probably came from eBay many years ago:

    Click image for larger version. 

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  2. #12
    Join Date
    Aug 2013
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    1,754
    Country: Wales

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    Well that figures if the padlocks recent enough for it to utilise die-casting then like I said that'd be the easiest and cheapest answer for mass production, but the last line of your post suggested you were asking how the warding plug was probably manufactured, so I assumed you didn't know.

    Machining or broaching unlikely? You might be amazed at what internal profiles can be produced by broaching and EDM. If you're thinking the processes couldnt generate a spiral or cut curves and bends internally then think again !

    On that note I'll throw this one in for fun- it's perfectly possible to drill an equally square hole in thick steel plate if you know how...and that's actually by cutting with a rotating bit to cut a hole that's a perfectly equal square...it's by no means rocket science and the set-up has been around donkeys years but it's amazing how many people think its impossible...

  3. #13
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    Dec 2009
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    Country: United States

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    When I originally wrote "I also would like to know how the warding plug was manufactured" I had just taken the lock apart and verified parts were non-magnetic (except the locking bar and shackle). I was incorrectly assuming the plug was brass but everything was dark and dirty. Later I started cleaning up the pieces with an ultrasonic cleaner and wire brush and noticed the plug was different and not brass-colored. Using a file yielded a pot-metal color and it "felt" like pot metal when filed. Having thus concluded it was really pot metal, I assumed it was cast because that's rather easy to do.

    Here is a picture of the key and plug:

    Click image for larger version. 

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    Yes, I've seen square-hole drills and they are quite interesting. Some YouTube videos (search for "square hole drilling" without the quotes, for example):

    https://www.youtube.com/watch?v=ALiqAXiTQBg

    https://www.youtube.com/watch?v=rjckF0-VeGI

    https://www.youtube.com/watch?v=L5AzbDJ7KYI

  4. #14
    Join Date
    Oct 2009
    Location
    Cleveland, Ohio USA
    Posts
    1,433
    Country: United States

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    I don't know, it looks like rocket science to me. Realeaux triangles, Wankle engines with flattened sides to allow for a combustion area, scalloped sides to allow for a cutting edge. All these things I didn't learn in high school.

  5. #15
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    Dec 2009
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    Country: United States

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    Another problem with this particular style of Twiskee: the key is not symmetric. Unless you are observant about the position of the stamp on the case, you will probably insert the key in the wrong direction half the time, pull it out, and re-insert in the correct direction. In the process, the key will slowly chew away at the profile wards (correct term?) in the plug since pot metal is so soft. So it's not very convient and given enough time and hard use, the wards may disappear. At that point a plain key might work the lock. I have to admit this is a fairly unlikely attack but there is still the aspect of convenience.

    In this example plug the wards are almost entirely gone. The lock seems to have been abused at the end of its life and possibly before that.

    A better design would have been a symmetric key but there's no way to know what went into the decision-making at the time.

  6. #16
    Join Date
    May 2016
    Posts
    27
    Country: UK

    Default "Twiskee"-Milwaukee Lock and Mfg Co

    Amazing that there was an earlier twisted key patent! The one used on this lock was by Christian Buehner- US 1849070. It took me ages to find, but I found the excellent -antique-padlocks-com could have saved me many hours, if I had not looked there first!

    Thanks to wylk's investigation, the actual lock was shown to also use a lateral locking pin in the bolt, which is notdepicted on the patent. A picking expert on the internet was disappointed by the ease with which he was able to violate a "Twiskee", using a hard lockpick forced through the diecast plug-what agonies it must have suffered!

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