Large blind holes

[sum1]

Wife saw these wine racks, I am now tasked with creating a much larger one out of a spruce burl we have in the yard.

How are these large blind holes made? Looking at some wine bottles in my house they must be around 3.5" diameter.

Forstner bit? Some type of hole saw?  

I think breaking off the center of the hole saw could be an issue trying to get the blind hole somewhat flat.

[21incher]

I would think a forstner bit would work with an extension.  They can be tough to feed by hand so a large  drill press may work.  Most only have 4 to 5 inch quill travel so the table would need to beraised several  times and a vacuum hose to pull the chips out. 
More expensive option would  be find someone with a big water jet. 

[rusticretreater]

A large Forstner bit, or

A hole saw on an extension.  Cut to the depth of the hole saw, pull it out.  Chisel out the center. Repeat.

[beenthere]

A machine lathe also a possibility. Takes some ingenuity to do, but helped a business years back that would bore such holes to make wood vases and table lamps, prior to chucking in a pattern lathe or duplicating lathe to shape the outside of the pieces. 

[chet]

My go to method for something like that has always been a Forstner bit, coupled with a hole hog or large drill press. 

[doc henderson]

my wife would not like that cause the bottles are mostly empty! ??? 8)

[Hilltop366]

Could use both, use the hole saw to cut the outer circumference and a smaller 1"ish  forstner or sawtooth bit to hog out the centre with several holes then a small aggressive disc on a long arbour to smooth out the bottom. Could be done with a 1/2" drill as you would need a very large drill press to reach all around a large slab. 

[chet]

I use an extension on the bit, then raise the table each time I reach the max depth of the drill press. For those times that the drill press is not an option I use the hole hog.

[21incher]

my wife would not like that cause the bottles are mostly empty! ??? 8)

I bet it took one bottle for killing the pain of each hole drilled 🍾. That ain't going to be an easy job in a burl   . 

[Machinebuilder]

a water jet won't make a blind hole.

a big CNC machine would possibly be the easiest. Other than the tooling and the cost. ;D

I think a forstner bit would be my choice.

They are cool looking bottle racks

[21incher]

a water jet won't make a blind hole.

a big CNC machine would possibly be the easiest. Other than the tooling and the cost. ;D

I think a forstner bit would be my choice.

They are cool looking bottle racks

They are through holes. I have seen water jets cut through  3 feet of hardwood.
Edit.
Blowing  them up on the big monitor looks like only some are through so forstner bits probably will be the easiest. my long shaft die grinder with a kurtz burr would give that rustic look easily after  drilling.

[beenthere]

First drill a pilot hole, like 3/4" using a ships auger, or similar to go all the way through the wood. Then a forstner bit with a pilot the size of the pilot hole will follow that initial hole and bore straight.

https://www.carbideanddiamondtooling.com/Forstner-Self-Feeding-Wood-Drill-Bit-Interchangeable-Pilots-Individual-ID-15172-

[sum1]

I should have mentioned the burl I have is 36" diameter. Definitely not getting it into any machine and 100% blind holes. I think a forstner with centering pilot will be the way, I just can't picture my wrists being happy with a 3-5/8 bit.

[beenthere]

It won't be just "any" machine, but one such as a Bridgeport milling machine would work I believe. Not going to do these holes cheap, but do save your wrists. 

[Don P]

I just googled and got hits on "4" multi spur bit". 
After breaking a wrist I started buying clutched RA drills. On low 350 rpm there is a 75 ft-lb clutch that engages when it gets bound.