Purpose of odd double-ended drills?

Caliper jaws are 8" apart for scale. Ignore other items in lower right (roll stopper) and u. Left.

I posted these drills on the professional machinist site 12 hrs ago but they're still just guessing so thought I'd better post here too.

 

The bits with a smaller stepping up to a larger bore look to be for counter sinking screws, etc. The double ended thing throws me though. I can't remember ever seeing anything such as those.

 

I don't know how these drills were held so enough torque could be applied so they could cut through something. At least in metal-drilling drills, the lower half of the drill bit is reserved for the holding part, whether a Morse taper, straight shank, screw-threaded, etc.

 

Simply to have another sharp bit handy.
Sometimes they have a different cutting angle too.
They are likely more for a lathe for the chuck jaws are usually longer than a drill.
Usually best for many things to drill a smaller hole first and so those stepped ones will.

 

Thanks, all 6 drills have a long section with a sharp, protruding margin and a shorter opposite end that lacks sharp, shiny margin.

 

Thanks, Your Majesty! I 'spect after u enlarge the pic and think about this you'll return and post an updated opinion. Some of the machinist folks have already posted multiple times, later realizing there's something wrong with their last guess. Maybe they were left here by ET's whose laws of physics are different from ours here on earth; the drills worked on their planet but not on ours.

 

HA!
Hmmmmmm......

 

If ya give up I'll post link to an old Popular Mechanics article that tells the story. One of the machinists found it. I never would have guessed!

 

I never give up.
Have to cut my head off like an iguana....
But I'd like to see that...
And regardless of what it states...
Many tools can be used for other processes.

 

Here you go:

https://books.google.fi/books?id=gd...AQhPMAk#v=onepage&q=roll forged drill&f=false

 

I can't read that on my fArt smoNe.