Mystery Bolts

[Old Fart]

Was going through my grand-father's old tools and found a set of tapered bolts. One has a washer on it so I guess it's to seal something. Anyone know their purpose?

[Spock]

Being tapered & with the fluted sides, they would be self taping metal bolts
No way they would be for wood

[5.4MarkVIII]

Could be wrong but if I remember correctly there was a time where drain plugs were not a thing. These allowed one to add a drain plug to engine or trans pans.

[5.4MarkVIII]

Could be wrong but if I remember correctly there was a time where drain plugs were not a thing. These allowed one to add a drain plug to engine or trans pans.

Possibly more farm related than auto?

[bbriann]

Larger ones are used in cast aluminum oil pans when original threads deteriorated as 5.4mark already mentioned.

[Old Fart]

Grandpa was a Ford/GM mechanic so it would make sense that they would be drain plugs.

[redo75]

Old world mechanics used to put the screws to customers. Start small and then work up to big end.