SPAs on Twist Drills

[RichColvin]

Dan Heil contacted me by eMail and noted,

You can grind a SPA by setting the (DBS-22 clearance angle) to 90 degrees.

I tried it and that indeed worked ... exceptionally well!  Here is the resulting grind on a ½" drill bit.

This is a really big find by Dan as SPAs are really good on larger drill bits, and as noted on GadgetBuilder,

Secondary Point Angles ... extend drill life, improve hole finish and minimize the exit burr on through-drilled holes.

You can also see that the secondary facets are quite a bit rougher than the primary facets. This is due to using a different grinding wheel, making this a faster process

Primary Facets	Started with DC-250 diamond course grinding wheel (drill was in bad shape) Finished with DF-250 diamond fine grinding wheel
Secondary Facets	Used DC-250 diamond course grinding wheel
SPAs	Used DF-250 diamond fine grinding wheel

[Rossy66]

Dan Heil contacted me by eMail and noted,

You can grind a SPA by setting the (DBS-22 clearance angle) to 90 degrees.

I tried it and that indeed worked ... exceptionally well!  Here is the resulting grind on a ½" drill bit.

This is a really big find by Dan as SPAs are really good on larger drill bits, and as noted on GadgetBuilder,

Secondary Point Angles ... extend drill life, improve hole finish and minimize the exit burr on through-drilled holes.

You can also see that the secondary facets are quite a bit rougher than the primary facets. This is due to using a different grinding wheel, making this a faster process

Primary Facets	Started with DC-250 diamond course grinding wheel (drill was in bad shape) Finished with DF-250 diamond fine grinding wheel
Secondary Facets	Used DC-250 diamond course grinding wheel
SPAs	Used DF-250 diamond fine grinding wheel

That's really cool.