Quote Originally Posted by John S View Post
No just one hole, left to right, right to left can be obtained by reversing the bobbin direction.


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i'm not sure I'm following?

I can't change the parts around from side to side as they have different 'pocket' depths milled into their end bits (this is becuase I need different amounts of magnet core to protrude outside the copper coil at each end). Also each part is held in a different manner ... ie part 1 is held by a drill chuck, whereas part 2 is threaded onto some M8 rod. Therefore if I need to start the coil winding at a different end, then they both need the 'start' holes drilled.

But as Bill helpfully mentioned...the 0.5mm hole wouldn't need to go the whole way, just the last say 0.3mm if drillling from the main rod perimeter down towards the part 1 end surface.