enlarged shank drill bits, why?

In my collection of random drill bits I have several around 1/4-1/8 inch that have a larger shank then the main drill body. Why? is it like silver and demming bits in reverse so they all fit into one size collet? they seem to be well made. Not junk made by someone who knows very little about drills. Some have a factory coating so not resharps.
I can understand it with the tiny carbide bits that are needle sized just to be able to see the end to place it into the chuck.
Seems like grinding away all that extra metal would take time and money.
Bill D

Are the shanks 1/2"? I seem to remember reading somewhere that many of the old old pillar drills didn't have drill chucks but had a 1/2" "weldon" style holder with a set screw, and that drill bits were sold stepped up or down to a 1/2" shank to match it. Deming drills are still common just because they're handy, even though drill chucks and collets are now the standard. We've got a little old hand crank pillar drill in the shop with the old set-screw spindle, but it needs a chuck adapter to use as we don't have any 1/2" shank bits under 1/2" diameter (it's more of a decoration at this point, but it gets used occasionally).

Around 1955 or so, I wanted a 1" drill bit for something not wood, though I have forgotten what the job was. The big downtown hardware store only had a 31/32" carbon steel bit with a 1/2" shank and a single flat on the shank, so that is what I got. I think I still have it.

Old blacksmith shop post drills had spindles with 1/2" holes and set screws to hold drill bits with 1/2" shanks with a flat for the screws. So there were lots of bits made in all useful sizes, whether larger or smaller than 1/2", but all with 1/2" shanks. Another solution was a chuck with a 1/2" straight shank that could hold small drill bits with ordinary shanks. Eventually, 1/2" chucks became more common than the 1/2" holes on drill presses. Jacobs chucks are not convenient for holding the old-style shanks with one flat, but bits with 1/2" shanks and larger cutting ends were still useful in 1/2" capacity chucks. That is why those "Silver and Deming" bits you see for sale now do not have that single flat on the shank, but some have three flats for better grip in a Jacobs chuck.

I have a faint memory of seeing some bits with 3/8" straight shanks and smaller cutting ends, but forgot where.

Larry.

They might also have been destined for use on a turret lathe.

Bill D said:

Seems like grinding away all that extra metal would take time and money.
Bill D

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Shank size?

Moore offered "reamer drills" with 3/8 and 1/2-inch shanks, as well as "short drills" with 33/64 and 49/64 shanks. They allow for "maximum work height under the spindle".

Drill size about 1/16-1/8". shank around 1/4-3/8". some metric some English sizes.
Bill D

Perhaps a dumb thinking on my part, but what about having a standard shank size over a range of drill sizes to use with adjustable ( floating ) holders?

Say a complete set of drills from 1/8 through 3/8, all having the same shank.
Once you dial in your drill holder to be on center, you can just swap the drills out at will as they will all be on center.

Similar to floating reamer holders.
I have a range of reamers, like 20 or so sizes that all share the same shank size, except in this case the shank is smaller than the business end.
I still use those from time to time for PITA jobs on the Hardinge chucker.

A large chuck on a big machine may not be able to close tight enough to grab on to a 1/16 inch bit. So therefore they made the shank bigger so a small bit can be used in a big machine.

Superbowl said:

A large chuck on a big machine may not be able to close tight enough to grab on to a 1/16 inch bit. So therefore they made the shank bigger so a small bit can be used in a big machine.

Click to expand...

This ^^ sounds most logical to me. Standard size quick change holder could be a possible use also but doubt that's why they were manufactured. I've never seen them advertised for sell as new in a set. My guess is the few that are out there are the only ones left, take care of them.

Brent

Can't speak for the specific example but I have some nominal sized drills for specific applications, for example,

4.2mm drill with nominal (6mm) shank, I can throw it into a standard 6mm reducer bushing in my Emco lathe and have it stick out of the turret about an inch less than if I used an ER16 or ER20 collet chuck and avoid a lot of clearance issues with it being a small lathe. I'd guess a drill like that would also reduce runout in a collet chuck too as you're clamping the nominal collet size.

Downside is they're way more expensive than regular drills and not as easy to get, main reason I have them is I found someone with a huge amount of NOS quality German nominal shank drills at silly low prices so I grabbed anything I thought might be useful, turns out they have been.

M.B. Naegle said:

Are the shanks 1/2"? I seem to remember reading somewhere that many of the old old pillar drills didn't have drill chucks but had a 1/2" "weldon" style holder with a set screw, and that drill bits were sold stepped up or down to a 1/2" shank to match it. Deming drills are still common just because they're handy, even though drill chucks and collets are now the standard. We've got a little old hand crank pillar drill in the shop with the old set-screw spindle, but it needs a chuck adapter to use as we don't have any 1/2" shank bits under 1/2" diameter (it's more of a decoration at this point, but it gets used occasionally).

Click to expand...

That is also the case with a standard Cole Drill. Chucks with a 1/2" shank were an option.

Never seen HSS like that, but common for high performance carbide drills. Alot of those will have a standard 6-8mm shank with an undesize cutting diameter to use in shrink fits and endmil holders.

I've seen a couple of examples examples.

Circuit board drills are all 1/8" shank and have a plastic depth setting ring installed at the factory. So operator just jams in drill bit to the stop collar and it is already set to depth. These on high speed spindles drilling and milling fiberglass circuit board material.

My CNC wood router has 11 auxiliary spindles. They are physically quite close to each other and clustered around the main HSK64 spindle and the grooving saw. There isn't room for much in the way of collets. So they all seem to have a common size (3/8"? or 1/2"?) shank on them. I'm guessing they are a standard item in the wood routing world.