Cheers for the interesting reads guys. The spade drills safeman posted are certainly the more common drill bits of that period and typically used for drilling holes up to say, three quarter inch diameter, inch perhaps at most. Hard work by hand under the easiest of conditions, but throw the hardest steels of the day into the equation and it gets much harder. Yes there are countless age-old tricks for hardening them like safeman pointed out, but it must have been painfully slow as I’d expect they achieved little more in terms of superior hardness than the material they were drilling. That was probably the easy bit though as we all find ways around problems, it’s the big diameter holes with what appear to be the hole saw type annular cutters that seem the biggest mystery.
The more I look at Dougs 1890s picture the more I’m blown away by it. That size of hole through that thickness of hard and laminated material is incredible, and all done by arm power.
The flame softening technique could explain things to a certain extent, but as Doug says in those tests there’s no equipment visible and no mention of it either.
My very distant and limited experience of oxyacetylene use in this application made me realise that a relatively large outer hole is needed in order for it to work effectively. The thicker the outer plate covering the hard steel underneath, the larger the outer hole needs to be in order to concentrate that flame effectively down onto the hard plate inside. The gas torch setup safeman posted is an amazing bit of kit for the time, and it’s clear from the sketch its being used down a pretty large diameter hole, which isn’t a problem in the majority of cases where the outer plate is mild. It’s the large cored holes straight through the Bankers doors without softening that’s got me scratching my head.
Guys I’m not doubting or questioning what you’re saying here, and apologies if it came across like that, I’m in agreement with the individual points you’re making, it’s just that collectively they still leave the annular cutter mystery open. Safeman, yes the soft outer plate on the Chatwood answers the thread tapping mystery, that was down to me thinking the outer door skin was hardened like the GP and Ratner’s.
Doug I agree that using a grinding paste on the large diameter holes would be slow. So slow I just can’t see it working with arm power, not even in a week! One thing I noticed in the Chubb Collectanea book makes a few references to the standard hole saws available, but this was much later than what were talking here, and even in 1926 the Enox range of so-called ‘Ring Saws’, stopped at 3 inch diameter. These were what were used in the 1920s London safe attacks, which as we know turned out to be only lightweight fire resistant safes, being misused for the storage of valuables. Obviously Useless on the hardened steels of the burglary resistant and bankers safes were talking about here.
It’s definitely an absorbing subject, and it’s sure got me thinking. I wouldn’t want to compete with that 1890s picture in a mock-up test, and that’d be with an open catalogue choice of coated/tipped cutters, AND the power of a one horsepower motor!
