Unusual auger bits

[Pete W]

Spent the last day or so derusting and cleaning several bunches of bits acquired from eBay over the last few months and came across a couple of unusual design.

They're what I thought of as 'shell augers'; however, after spending several hours googling that term I've come up with nothing like these bits (most of what I found online under the name 'shell auger' are what I'd call spoon bits).

They're essentially a standard auger but with an enclosed head where the spiral thread becomes a hole running through the latter couple of centimetres.

What's weird is that I'm sure I've seen countersinks of similar design and thought they were called 'shell countersinks' or 'snailshell countersinks', but I haven't been able to find any reference to those either :?

They look more difficult (or at least more expensive) to manufacture than normal auger bits, so there was - presumably - a specific purpose for them. Anyone have an idea what that was?

Pete, puzzled

 

[Colin C]

Hi Pete

I think Alf has some of them and will know what they are called, plus i think she has posted pic's of them too

 

[MrJay]

I've got a bunch of them. That's as much as I know though.

 

[Alf]

Hey up, Pete,

Sounds like a Solid Nose aka Bullnose aka Unbreakable? Auger on the right here? (Scroll down a bit for their uses) The countersink you're thinking of is probably the Snail countersink? Most excellent design; I held out on buying one for a long time and regret the many years of unnecessary suffering of countersink chatter that preceded the purchase. #-o

Cheers, Alf

 

[Pete W]

Sounds like a Solid Nose aka Bullnose aka Unbreakable? Auger on the right here?

Right first time

The countersink you're thinking of is probably the Snail countersink?

And again... that's the one! Snails, shells - you can see where someone might get confused

Somehow, I seem to have acquired an extensive selection of brace bits, as well as several countersinks (sadly not of the snail type). When I've got all the muck off 'em I'll try to remember and post a pic or two.

Pete