Hand grinding a flat bottom drill.

[Jimsehr]

Turning a Harbor Freight drill into a flat bottom drill.

https://photos.app.goo.gl/cFSx3uBtlJKqWXA42

 

[BtoVin83]

Impressive! Good eye and motor control

 

[Karl_T]

you made it center cutting, that's hard to do. I have done several for countersinking socket head cap screws after drilling the through hole for the screw. that is a piece of cake.

 

[RJSakowski]

I've made many custom counterbores in this fashion over the years, the smallest being for a #2 socket head cap screw.

One piece of advice when using them; is to pre-drill the hole with a standard drill to prevent the counterbore from wandering.

 

[T Bredehoft]

And keeping it as short as you can, again to keep it from wandering.