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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.
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Did you see this ? Countersink Drill Bit making
Rotatable & Adjustable Wooden Smartphone Stand. You can rotate the phone 360°.

When you watch this video, you can learn to make a center marking tool. The center finder is a useful tool for woodworking. You can mark a cylinder or square.