Important: I would like to keep the PDF documents and plans I produce free of charge. Please support me with your likes and comments.
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 :
Go to this video's Youtube page and make a comment.
Did you see this ? Countersink Drill Bit making

I make long C clamps using some hard plywood. You can do a lot of compression with these extra powerful clamps. It is very useful thanks to its long arms.