Sharpening drill bits...

[brightspark]

no twist drill can produce an accurate round hole that's where reamers are required

 

[daleyd]

id imagine they would be a tad more than HSS too...

I don't think they are massively special TBH, they are only drilling ali. (Good quality mind, just not exotic material)

 

[ukracer]

Has anyone tried making this. seems very cheap for plans..