World's Largest Round Vault Door

[Safeone]

Thats always amazed me how a soft steel paper clip imprinted the frame of the largest, heaviest and thickest vault door ever made. Always assumed the door casting would have been a relatively tough steel, but the fact the soft steel paper clip imprinted the circular frame means the frame can only be soft mild steel- perhaps there is a matching print on the door as well but my guess is the door would (hopefully) be tougher and that would have helped impact the clear print in the frame.

I would have expected the soft paper clip to be softer than either the door or frame, and for it to have been squashed as flat as a sheet of paper. It's interesting as soft mild steel used on such a massive door frame where the frame actually houses all the locking controls and the locks, doesn't inspire me with confidence except for the fact the controls are 5 or 6 foot away from you!

It actually makes me wonder just how secure some of those massive doors really were, almost to the point of safety in brute thickness alone being the primary thinking, and also the resulting 'intimidation factor' it produced, over more critical issues of defensive materials and equal protection covering the door and the locking mechanism as a whole.

My thoughts echo yours. Thought it would have simply flattened to feeler gauge thickness then fell out

[Huw Eastwood]

Looks like I've got some catching up to do on this thread

kwoswalt99- you said that you wouldn't think the paper clip would squash flat even if the door was hardened steel?
I should have been more specific when I referred to a 'relatively tough steel' in that I meant steels with a high tensile strength and lower malleability, not hardened, but a grade typical for the door casting and the frame structure of an installation like the Cleveland Fed door.

Hardened steel is something else above high tensile steels, and if the CF door was hardened then it would've been the vault equivalent of a hydraulic press! Think about what would be happening there:

A Soft thin workpiece with a tiny surface area (the paper clip), resting on a tough steel base (the frame) + 100 tons(?) of hardened steel surface area, swinging horizontally on roller bearings (the door) + 30 or 40 tons (?) of additional slow clamping pressure (the pressure mech) = totally flat paper clip. It's Simple physics, and the concept behind the process of pressing components in industry to this very day.

My guess would've been the door and frame would be a relatively tough high tensile steel casting, but bearing in mind how soft paper clips are, (the type of the traditional pattern that's imprinted- they're not normally made from 'spring steel'), it would still result in the clip being flattened like a pancake. Like you pointed out, we already know that the door plug itself wasn't hardened as they hand filed and scraped it to fit afterwards, but I'd have expected both door casting and the frame vestibule to be a 'tougher' steel than the paper clip, and bearing in mind the tight tolerance between door and frame, the weights and pressures involved, it should all Add up to a paper clip flattened out very thin. The fact that it didn't, makes me question 2 things- how hard was the tiny paper clip, and/or how soft are the door and frame?

Maik- you'd be amazed at what drills are available off the shelf! I know we're talking 1930s in the case of the CF door, but I've had off the shelf Presto twist drills in 1/4", 5/16", 3/8", 1/2", 5/8" diameters in 18 inch, 24 inch and 36 inch lengths...ridiculously expensive but that's standard 'long length stock' for the serious manufacturers. I'm sure that other companies and those in Germany like Guhring would offer the same. In fact I use a lot of Guhring spiral machine taps for machine and hand threading, but haven't got that many of their drills. Also, bear in mind that these were just standard options, what's used in specialised industry would dwarf these and make them seem like toys.

Plus, as Doug pointed out, criminal safe attacks also breed the same engenuitive thinking as 'honest and legally operating' safe engineers like I was for many years. It's not difficult to make your own specialised drills or extended drills, and I've still got long drill bits, screw drivers, sockets and opening tools that I've made, modified and used over the years.

When you referred to carbide drills with coolant channels, they're the obvious choice in industry when drilling a workpiece being flooded with soluble oil that's fixed on a machine, but that's where their use is limited.

Safe engineers working out on site don't have that level of luxury or need it, it's all done with a variety of tipped drills with the tips purpose ground for the job. When you're stuck on a Jewellers or Bankers grade safe trying to drill an inspection hole through ridiculously hard barrier material, while squashed into an impossibly tight corner on a concrete floor, for hours, and even days, it also leads to the same creativity, engenuity, and alternative thinking from outside the box- you might be amazed at what we come up with.

One thing that's really confused me-

Your beautiful and impressive Wischeroop drill press, that can drill 40mm holes in stainless steel, and tap massive M33 threads- now that's big, seriously big, but you then said you struggle with it to drill a 10mm hole in the low carbon steel of your model door?

The largest thread I've tapped in 316 stainless is M16- that's massive to me but very small compared to your M33. My 8 inch swing APTC lathe couldn't handle it, so a call to J&L's technical team resulted in a hand tap, die and wrench set-up, (at ridiculous cost), to cut them by hand...and the wrench is about 3 foot wide....and I still struggled to get enough torque on it with floods of mineral oil and the workpiece bolted to a 500 kilo bench! And that was M16 compared to M33, and you say you struggle to drill a 10mm hole through low carbon mild steel?

[mercury]

I have no formal knowledge or experience with metallurgy, so my suggestion could well be quite absurd, but is it possible that the paperclip was work hardened by the pressure of the door closing on it, this protecting it somewhat from further deformation?

I do know that plastic deformation, caused by squeezing can work harden an alloy, but I have no idea if it would be a significant factor in the case of the paperclip vs the door+frame.


...Mark