Drilling very wet, very hard wood

[toolsntat]

A Shell Auger, nose auger, pod auger, split nose auger (all the same thing) with lipped cutting edge should help here to pull in as you turn and cut.
Cheers Andy

 

[Ollie78]

An auger bit is certainly the right tool but perhaps you need a slightly different pattern to assist with the very hard surface. I think you might need to keep sharpenning the bit or find something with replaceable tips.
I have seen some japanese pattern auger type bits with less "flat" at the bottom if that makes sense. These look like the sort of thing Star-M Japanese F-Type Auger Bit - Singles

Or perhaps something like the souber lock jig uses, it has replaceable carbide tips like a router bit brazed into it. They screw on to a smaller diameter bar which would reduce friction compared to a standard type auger and they go pretty long as well.
You can see the drills and replacement tips here.
https://www.morticer.com/en/dbb-morticer-accessories/
Ollie

 

[LJM]

Ah. Okay. Yeah, that gets pretty complicated. Sorry - wasn’t trying to teach you to suck eggs, just trying to figure out why the chamber couldn’t be drained...

All I can think of is the same as @Argus - something like a 8mm pilot hole to allow the centering bit of the augur to get continual purchase on something and to stop the augur just skidding on the face?

Good luck!

yeah, I’ve been thinking pilot hole, thoug

An auger bit is certainly the right tool but perhaps you need a slightly different pattern to assist with the very hard surface. I think you might need to keep sharpenning the bit or find something with replaceable tips.
I have seen some japanese pattern auger type bits with less "flat" at the bottom if that makes sense. These look like the sort of thing Star-M Japanese F-Type Auger Bit - Singles

Or perhaps something like the souber lock jig uses, it has replaceable carbide tips like a router bit brazed into it. They screw on to a smaller diameter bar which would reduce friction compared to a standard type auger and they go pretty long as well.
You can see the drills and replacement tips here.
https://www.morticer.com/en/dbb-morticer-accessories/
Ollie

That could be worth investigating!

 

[TheTiddles]

Suction cup the drill onto the gate and use the same vacuum supply to pull the drill into the material like you would with a mag-drill on metal. Sounds like a cool thing to make, I’d love to have a go if time allowed. A university might find it an interesting challenge

 

[Limey Lurker]

Once you have got to the maximum depth with your auger, try a similar sized auger with the screw ground off, and if you can find a toolmaker, with the cutting edges extended to the centre. A skilled man could do it by hand on a bench grinder.

 

[gdjm]

I’m working on a project that requires the drilling of very wet greenheart; it’s underwater, so there is no way around the fact that it’s wet.

Holes need to be 26mm diameter, c. 300mm deep. The drill is hydraulic. Auger bits have been tried; they cut nicely through the fist 30mm or so, then simply stop cutting in to the timber. Standard twist drills don’t fair much better.

Keeping in mind that these are being drilled free-hand, mid-water, and need to be accurate (so that the fabricated fixtures fit), I’m looking for possible solutions to this problem... any thoughts?

How interesting. I’ve drilled and milled miles of green heart and whilst it dulls steel fast it never stopped them ( blades or drill bits )

I’m working on a project that requires the drilling of very wet greenheart; it’s underwater, so there is no way around the fact that it’s wet.

Holes need to be 26mm diameter, c. 300mm deep. The drill is hydraulic. Auger bits have been tried; they cut nicely through the fist 30mm or so, then simply stop cutting in to the timber. Standard twist drills don’t fair much better.

Keeping in mind that these are being drilled free-hand, mid-water, and need to be accurate (so that the fabricated fixtures fit), I’m looking for possible solutions to this problem... any thoughts?

How very interesting, I milled up and drilled loads of green heart. Yes it dulled the tools . But never STOPPED them as you are describing.. Is it possible there is something like an iron plate reinforcement in there . Test with a magnet or possibly even a stud finder . Other than that I’d spring for a set of cobalt bits lubed with grease and see if they can pierce through whatever’s there . Keep us posted . Love to hear what finally works for you.
Any photos ?

 

[Fergie 307]

I would have thought a carbide twist drill with a good rake so you have a narrow cutting edge will do the trick. These will cut through hardened steel. The usual problem with cutting a big hole in wood with a twist drill is that the friction heats the wood up. It then expands and grips the flutes, causing even more heat and an even tighter grip until it just binds up And the heat will quickly blunt a steel drill. Drilling underwater I would have thought would eliminate that problem. In any case a carbide tool won't mind a bit of heat, they like being worked hard. Question would be can your drill drive it at the right speed, I'm guessing something like 100rpm as a starting point.