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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
In this DIY video I build a wooden lathe. I used very hard plywood to make this lathe. Building a bit long, but it was worth it. Because I built a very robust lathe...

You can use it both to drill 90 degree holes and to drill holes in the depth you want. It also works for joining two woods together, you can see in the video.