In this video, I make an adjustable drill bit. I start by using the metal I cut from the M12 bolt. Then I am cutting a Spade Drill Bit. Then I combine the two.
Making Video :
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Did you see this ? Countersink Drill Bit making
I updated my Drum Sander. This drum sander now has a motorized slide. No need to use your hands anymore to push and pull.