Terry Filter Safety Gap

Today I picked up a parcel from the local Royal Mail depot. Inside was four long awaited 60mm bolts (should have been 8), least I can make a start on the safety gap. First I need to tap 2 holes through the 2 1" brass balls obtained from Teslastuff.com. The holes need to be 5mm which is the size required if tapping out to M6 with 1.0mm threads. The pic below shows how I mounted them for drilling.









I screwed in the bolt to the existing tapped hole to help me drill at 90 degrees to the existing hole. The bolt also prevented the brass ball spinning in the chuck jaws during drilling. It was easy to find the centre point for drilling as I could spin the work in the chuck to show any mis-alignment. After drilling with the centre drill I drilled a 5mm hole completely through each ball.









Next I tapped the holes out to M6 1.0mm threads. Note the plastic jaw covers on the vice to prevent marking my balls!!!









I then polished my balls by mounting them onto a threaded stud held in the chuck and spinning them up against various grades of emery cloth.









The finished articles almost ready to mount on ceramic insulators on the Terry Filter.









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