Mosler Defender: tamper-resistant screws

[wylk]

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?

[Huw Eastwood]

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 .

[wylk]

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 --



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 --



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.

[Huw Eastwood]

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.

[wylk]

It did send me off on a quick search for security bits on eBay but none look like Mosler's style. I did find a new style I hadn't seen before, "LOX" which is a modified square drive. But that's not relevant.

I think it's fascinating that Mosler chose this particular type of tamper-resistant screw, that today is virtually impossible to find a driver for. Were they really that worried about unauthorized access to the timer?

I'll keep looking, or at least keep my eyes open. If a commercial bit is found I'll follow up in this thread.

[Huw Eastwood]

Wylk you’ll find this hard to believe but I’m being totally serious in that another famous maker also for reasons unknown, chose that particular type of screw. What famous maker in question ? You’d better sit down for this and perhaps even pour yourself a whiskey. Fisher Price. They used them on countless toy and plastic products throughout the 1970s but notoriously on the record players which prevented joe public from doing their own diy repairs !!!

[wylk]

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?

[wylk]

Wow! That's unexpected but fun to find. Here are a couple of images and they do look just like the Moslers:

[wylk]

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

[Huw Eastwood]

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.