Fingerprints. Despite what you may have seen on TV, fingerprints are far from unique. Especially for only a single digit and with partials.
I worked on a security sensitive project involving finger print readers, and we concluded that the readings would collide for about 1 in 500 people of the same race. We decided to insist on a 5 finger match. More sensitive readers probably reduce the collisions, but ink isn't very precise
And anecdotally, my son can open my wife's phone with his thumb matching her thumbprint. It is an Apple product
Anyway, as far as I know, a zip disk is an abrasive wheel. Instead of 'cutting' it off, you might as well keep grinding
HSS is a family of alloys. Not every one the same. IIRC HSS was developed due to a lack of Tungsten when Molybdenum had to be substituted due to shortages during one of the wars. There are at least 10 different standard grades. And who knows how many non-standard ones. Standard alloying agents include Cr, Mo, W, V, Co, Mn, Si and probably more - along with the Iron & Carbon that makes it steel
I worked on a security sensitive project involving finger print readers, and we concluded that the readings would collide for about 1 in 500 people of the same race. We decided to insist on a 5 finger match. More sensitive readers probably reduce the collisions, but ink isn't very precise
And anecdotally, my son can open my wife's phone with his thumb matching her thumbprint. It is an Apple product
Anyway, as far as I know, a zip disk is an abrasive wheel. Instead of 'cutting' it off, you might as well keep grinding
HSS is a family of alloys. Not every one the same. IIRC HSS was developed due to a lack of Tungsten when Molybdenum had to be substituted due to shortages during one of the wars. There are at least 10 different standard grades. And who knows how many non-standard ones. Standard alloying agents include Cr, Mo, W, V, Co, Mn, Si and probably more - along with the Iron & Carbon that makes it steel