Hello Jordan.
My suspicion is the countersinking work was done by someone who was using the bridge for a purpose other than its original intent. It makes no sense at all in any wireless applications I have ever seen. The bridge is designed as an intermediary component in a wireless installation, not an end component where a nice hidden bit of hardware is required.
I have seen variations in metal thicknesses over the years, as well as subtle variations in the angles/shape of the metal bits which are probably manufacturer variations. When placed side by side, these various bridges all showed the same height and spread between the mounting holes in the feet. These, it would seem, were the two critical measurements.
What I have seen over time, is that a small number of these bridges turn up with no BA threading at all in the top holes. Drilled smooth. I think this is a post war mod when supplies of BA hardware where dropping out of the supply system.
The reason the bridges were threaded in the first place was because some wireless installations have precious little room to get a spanner down underneath the bridge to access a nut. The process of installation would have been to mount the bridges with easy access to the required hardware. Then the wireless carrier would be mounted to the bridges. Since the bridges are threaded, and can no longer move when bolted down, the cheesehead BA screw has a round, internal thread lock washer placed between the head of the screw and the carrier face to prevent it from loosening when run home.
Once the top threads of the bridge are drilled out, you have no choice but place a lock washer and nut down under the bridge, the lock washer between the nut and the underside of the bridge to prevent the nut from loosening. This won't work with limited access in some installations.
Hope this makes sense. I haven't had my morning cup of tea yet.
David
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