Drilling very wet, very hard wood

[LJM]

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?

 

[Argus]

Accurate pilot hole first, then successively thicker drills to the required diameter?

...................awful lotta work. What's it for?

 

[LJM]

Repairs to a lock gate. Oh, I forgot to mention; there is no visibility, so working blind. One of several reasons that centering the drill is challenging and so a pilot hole could prove problematic.

 

[RobinBHM]

I wouldve thought drilling holes in a lockgate...kind of defeats the purpose

 

[LJM]

I wouldve thought drilling holes in a lockgate...kind of defeats the purpose

Don’t worry, its called job creation; there’ll soon be a vacancy for a boy to put his finger in it

 

[Inspector]

Can you screw a block with a hole in it to act as a drill guide for at least the first part of the hole? Is there a way you can get a clamp on feed for the drill? Something like a magnetic drill that you can apply more pressure on the bit. Hydraulic underwater Magnetic core drill | Ultimate Tools Something like this. Even if you have to clamp a steel plate to the lock and attach the mag drill to it.

Pete

 

[converse]

Make a jig and coach bolt it to the face? Water jet cutter? Drain a section of canal and take the gate off? Trench Piles around the gate and pump it out? Abrasive drill head with water lubrication?

 

[Cabinetman]

I think the only bit that will do it is the auger bit, it’s stopped digging because of a let up in pressure, would it be possible to use a ratchet strap through a pair of bolted on brackets (one each side of the hole) and over the top of the drill to maintain the pressure? Ian

 

[LJM]

Can you screw a block with a hole in it to act as a drill guide for at least the first part of the hole? Is there a way you can get a clamp on feed for the drill? Something like a magnetic drill that you can apply more pressure on the bit. Hydraulic underwater Magnetic core drill | Ultimate Tools Something like this. Even if you have to clamp a steel plate to the lock and attach the mag drill to it.

Pete

No, because there’s limited access to the point that needs drilling and the client won’t shell out!

 

[LJM]

Make a jig and coach bolt it to the face? Water jet cutter? Drain a section of canal and take the gate off? Trench Piles around the gate and pump it out? Abrasive drill head with water lubrication?

No; theses holes are for coach bolts, which simply won’t drive in otherwise. But also there is the access issue

 

[LJM]

I think the only bit that will do it is the auger bit, it’s stopped digging because of a let up in pressure, would it be possible to use a ratchet strap through a pair of bolted on brackets (one each side of the hole) and over the top of the drill to maintain the pressure? Ian

There was no let up in pressure, believe me! 40 minutes with all my weight behind , and no progressit; the first 30mm didn’t need anything like that.

 

[converse]

Some jobs can't be done at a price that the customer is prepared to pay. If you really are limited to someone in a wetsuit hanging off the lock gate, I'd try a few different types of drill bit with your existing set up (including metal bits), then I'd probably suggest a much bigger budget was going to be needed.

 

[smackie]

Oof. I don’t think I’ve ever seen the Canals and Rivers Trust (or British Waterways as was) ever attempt to do this underwater. There’s usually a deep groove in the stone lock chamber upstream and downstream of the gates to allow blanking timbers to be dropped in as a temporary dam that allows the lock to be drained for service.

That allows the usual gear to be used to service the gates.

 

[Darrenp]

Any chance the drill bit has hit an obstruction ???

 

[LJM]

Some jobs can't be done at a price that the customer is prepared to pay. If you really are limited to someone in a wetsuit hanging off the lock gate, I'd try a few different types of drill bit with your existing set up (including metal bits), then I'd probably suggest a much bigger budget was going to be needed.

Well it’s down to the client; we can’t lift the gates out (it would render the dock inoperable ), and the job is on a day rate, not a fixed price... so ultimately, do I really want the client to splash out on a piece of equipment that massively speeds up the job??

 

[LJM]

Oof. I don’t think I’ve ever seen the Canals and Rivers Trust (or British Waterways as was) ever attempt to do this underwater. There’s usually a deep groove in the stone lock chamber upstream and downstream of the gates to allow blanking timbers to be dropped in as a temporary dam that allows the lock to be drained for service.

That allows the usual gear to be used to service the gates.

Ive done it several times for CRT! Though they’re not the client in this instance.
They’re called stop-logs and stop-log channels; a big crane is required to lift them in and out, which the client is averse to. But they also close the lock.
Further to that is that these gates are on a tidal river, and the inner dock doesn’t run dry; massive pumps would also be needed to keep the gates dry

 

[LJM]

Ive done it several times for CRT! Though they’re not the client in this instance.

Any chance the drill bit has hit an obstruction ???

Not impossible, but the bottom of the hole feels very smooth; the auger is intact, so it’s not metal work in there

 

[smackie]

Ive done it several times for CRT! Though they’re not the client in this instance.
They’re called stop-logs and stop-log channels; a big crane is required to lift them in and out, which the client is averse to. But they also close the lock.
Further to that is that these gates are on a tidal river, and the inner dock doesn’t run dry; massive pumps would also be needed to keep the gates dry

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!

 

[Inspector]

Guess you are left with training shipworms to do the job. They will do just about anything for a nice piece of Mahogany at the end of the workday.

Pete

 

[Jake]

I take it you've eliminated bluntness, those types of timber are savage on cutters. TCT edged auger maybe? Augers for dense Hardwoods (timberfixings.com)