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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.
Making Video :
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Did you see this ? Countersink Drill Bit making
How to a make marking tool. 2 in 1 wood tool. Beam compass tool and marking gauge. Simple, homemade. You can mark to cut wood in the middle. You can draw a parallel line.

I only used wood to make the air blower. I mounted the pieces I made out of wood on an angle grinder. It turned out to be a wonderful air blower. It can blow very strong