Long story short I've drilled a 10mm hole in some 20mm Alu plate. The hole was to let me be sure that the ball screw shaft I had waiting for a coupler on the other side was in the right spot relative to the stepper motor I was going to secure to the plate. I had planned to use a 40mm holecutter to make the required hole and once positioned correctly mark out and attach a Nema23 stepper on the plate. Problem is the pilot hole for the hole cutter is 6.2mm the hole cutter does a nice tapdance on the plate but cant/wont cut accurately into the 10mm hole, I don't blame the holecutter, I blame me :)

So I believe what I need is a 10mm steel bar somewhere around 100mm long thats been turned down to 6.2mm for around 50mm of its length. Unless there's another way? (I've searched my collection of bolts etc for something that might do the job). Happy to reinburse someone for thier trouble. Thanks. Tony.