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  1. #1
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    Default Mosler Defender: tamper-resistant screws

    Mosler made a time-delay key lock called the Defender. In some examples it was built with conventional screws but some were made with a tamper-resistant screw. Can anybody name the type of screw and where to get a proper driver for it?

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  2. #2
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    TBH I think it’s Unlikely you’ll get a commercially made driver unless you or someone else makes one - that type of head is deliberately designed to engage only when tightening, the ramps/slopes present no edge or engaging surface when turned backwards to unscrew, so it repeatedly slips off and hence their common nickname over here - one way screws. The better ones are very tough and hardened so the critical ramp faces stay intact. There are countless different but similar variations of them made by different manufacturers worldwide.

    They differ from the countless other types which only need the specific matching shaped tip as those commonly encountered have positive engagement both ways - screwing and unscrewing, the ‘security’ being reliant on the unusual shapes they utilise, whereas your type there are deliberately shaped so that they present no positive engaging surfaces for removal.

    I made a few drivers to remove them about 20 years ago, the 2 blade variants from standard straight bladed screwdrivers but it was more difficult grinding precisely on the 3 bladed type like yours and found it easier to machine and file the ramps into blank silver steel bar (carbon tool steel common over here, think it’s called “drill rod”or similar in USA) and then harden and temper afterwards.

    Bear in mind if you do that its only the shallow angled sloping ramps that provide any mating contact for torque, so the resulting tool no matter how precisely made are never as effective at removing them as the positive edged one that drives them in, and exceptionally tight screws will always need a bit of technique and persuasion .

  3. #3
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    Thanks for the reply, but it may be hard to tell from the picture it's not a one-way screw. The sides of the slots are vertical on both sides. It seems close to what one company calls a Tampruf drive --

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    There are clear differences, primarily the steep slope, but also the fact the slots don't go to the center of the screw.

    I did make a driver that matches the Mosler screws --

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    And it did manage to loosen them all, without breaking, in spite of them being put in with some sort of thread locker. Mosler really didn't want anybody to get inside the case. I wonder if the Phillips-head variety came before or after the tamper-resistant variety.

    The original post was made in the hope that a "real" tool was known to locksmiths and that I could add it to my small arsenal of special tools for tamper-resistant screws.

  4. #4
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    your photos did have me wondering.... the first pic that shows the complete lock looks like they might possibly have edges on both sides, but the pic of the single fixing looks undoubtedly one-way (with ramps) to me.
    But, if theyre not like you’re saying, then drivers and bits will be available. I’ve got a cased set somewhere with Quite a few variations including the 3 blade propellor shapes with straight sides which aren’t for one-ways.

  5. #5
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    Photography of tiny things like that is tricky. I have thought about making a very short video while rotating a screw and the driver but it's unlikely I'll get around to it.

    I found a few promising drivers online but couldn't decide if they were the right size and slope:

    Tanner Bolt (New York) has a series of nuts and drivers they call Trident which includes a #6 driver (my screws are 6-32), go to their web site (https://www.tannerbolt.com) and search for Trident.

    Barnhill Bolt (New Mexico) has something called Tri-Groove but the pictures are especially poor. Go to their web site (http://www.barnhillbolt.com) and search for tri-groove.

    Spaenaur (Ontario) has something they call Tampruf. Go to their web site (https://spaenaur.com) and search for Tampruf.

    Even Amazon seems to have some of these.

    Huw, if you don't mind, what is the brand name and product number for your cased set?

  6. #6
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    There is a Mosler Defender for sale on eBay that uses Phillips-head screws.

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  7. #7
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    Its an old set and must be 15 years since I’ve even seen it tbh, even longer since I used it but it’s around somewhere in storage along with tons of other stuff. It was a cheap set back then, nothing fancy in a crude blow moulded case, also had an impact driver so could be Talco, it’ll show up sometime when I can post some pics.

  8. #8
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    Found the set wylk and the impact driver but still no clues , case and bits are unbranded not even a country of origin, the impact driver I thought was talco also unbranded but marked Taiwan- told you they were cheap !
    Btw couldn’t remember but there’s only the one flat nosed 3 bladed bit(front row second from right), all the others are the more common convex rounded points.
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  9. #9
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    Huw, thank you for digging those out. I do believe the one bit you refer to might be the correct one. At least, it resembles the bit I made.

  10. #10
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    Quote Originally Posted by Huw Eastwood View Post
    Found the set wylk and the impact driver but still no clues , case and bits are unbranded not even a country of origin, the impact driver I thought was talco also unbranded but marked Taiwan- told you they were cheap !
    Btw couldn’t remember but there’s only the one flat nosed 3 bladed bit(front row second from right), all the others are the more common convex rounded points.
    Harbor Freight Tools offers a 100 pc. security bit set for $7.99 that includes most anything you might ever encounter, made in China; see thumbnail and link:
    https://www.harborfreight.com/securi...-pc-68457.html
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    Pete Schifferli

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