Wed Oct 31, 2012 11:23 am by rai
And to find such holes, you tap the surface with a small ballpeen hammer, use the ball end. an even smaller such hammer can find capped holes in brushed brass padlocks, these holes are typically found over the pin drillings on the edge of the padlock, a larger one is higher on that edge where the locking dogs were installed,
these hole caps can often be seen if the brass that plugs the holes is of a different alloy mix (brass has between fourty to 60 percent copper and the majority of the rest is zinc.
sometimes bronze (90percent copper 10 percent tin) is mistaken for brass
brushing or filing the surface makes these visible caps dissapear until knocking about or corrosion reveals them
when a surface is tapped, it is then examined for tiny lines in perfect circles that are revealed by slightly sinking the surface.
on safes with filled holes is tapped these lines might occur if the threaded rod is at the surface and only hidden by grinding and painting,
when the lead is on the surface the peen will leave a distinct mark that cannot be made in the harder metal.
such marks reveal where a safe has been drilled to open and thus reveal where this can again be done but easier since the hardened metal is now gone. the mark will be positioned for aligning wheel gates.
wheel gates are now commonly aligned by use of a borescope, but before borescopes were widely available a wire was fished in to feel the gates and align them.
