Start your hole with a 13/16" first to depth as you have mentioned, then take your drill bit to
the grindingwheel and grind the tip off by turning [spinning]
Then with the side of the grinding wheel, you can gash the face [chip rake] to center, or one
cuttingede slightly longer then the other, so it will for sure cut thru the center.
Then grind the relief angle, about 5 to 8 degree.
You can also make you drill point more blunt, instead of 118 degr., something like 150 degr. so
the diameter of 13/16 will go deeper, what makes it better for the flat bottom drill, it gives you more guiding length!
Konrad
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Use a sharp tool & cut cool ! |