The 303 to 410 I did I started with a standard jobber bit, drilled as deep as I could then welded it to a smaller dia drill rod and did the rest. It ended up pretty true. Possibly not removing as much material or as deep as you though
The 303 to 410 I did I started with a standard jobber bit, drilled as deep as I could then welded it to a smaller dia drill rod and did the rest. It ended up pretty true. Possibly not removing as much material or as deep as you though
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