Snip
From: James Thompson
In another picture there is a mess of long auger bits measuring 18" in lemngth.
The strange part, to me at least, is that all of them are either 11 or 13. There
must be a reason why we find so many of these, and so few of other sizes. There
was also one 3/4" auger bit which is a full 24" long. I don't see many of those.
Unsnip

Dad was an Electrical Contractor. Dad always had a lot of 5/8 spade bits. We
used that size because it was small enough to bore through native oak beams with
a 3/8 drill and would pass two pieces of #12 romex.
When I emptied his shop I found four or five 1 1/4” spade bits in various states
of decay. He had been making bird houses but that seems a little big for
entrance holes.
I had already cleaned him out of auger bits. When he found spade bits made from
good steel he stopped using augers.