Drilling a 120mm dia hole ...

[RogerS]

A friend of mine is the manager at one of the Roman forts up here. They've got a larch that's been felled, very straight and about 400mm dia. They want to cut it into 1m lengths and then make a hole 120mm down the middle and about 300mm + deep. He asked me how to do it and I've not got much of an idea. Huge lathe ? Some machinery a shipwright would have ?

Any ideas ?

 

[Phil Pascoe]

Chain morticer?

 

[Inspector]

The old wood water pipes were drilled out by hand with an auger shaped much like a spoon or tapered bit for chairs. Get a blacksmith to make you one and eat a hearty breakfast.

Pete

 

[Trevanion]

My best guess if it needs to be accurate would be a large lathe rigged up with a steady rest and some serious boring gear.

Alternatively, for the brave, plunge cuts with the chainsaw or a chain morticer like Phil mentioned.

 

[Fitzroy]

My builder did a 120mm 400mm long hole through my granite wall for an extraction vent with a core borer, big Hilti drill thing that he attached to the wall, something they used for the brinksmat robbery. No idea if there is a wood coring equivalent.

F.

 

[RogerS]

My best guess if it needs to be accurate would be a large lathe rigged up with a steady rest and some serious boring gear.

Alternatively, for the brave, plunge cuts with the chainsaw or a chain morticer like Phil mentioned.

They tried with a chainsaw but the sides were, not surprisingly very ragged. They have an old piece as reference and that is circular so it can be done.

 

[RogerS]

My builder did a 120mm 400mm long hole through my granite wall for an extraction vent with a core borer, big Hilti drill thing that he attached to the wall, something they used for the brinksmat robbery. No idea if there is a wood coring equivalent.

F.

If there is I can't locate one.

 

[Trevanion]

Now, hear me out...

120mm saw blade in an angle grinder that is attached to a drill and slowly fed into the workpiece....

Yeah, maybe that one is for the stupid :lol:

 

[AndyT]

If you want to be anything like historically correct, have a look at this little video. It's in German but the pictures speak for themselves.

[youtube]zraPiBS0Fw4[/youtube]

 

[Sheffield Tony]

Looks like a giant version of a flute maker's auger ... and what are the chances of getting one of those in 120mm diameter ...

 

[marcros]

is cutting it in half lengthways, scooping out the middle and rejoining out of the question?

 

[cookiemonster]

A 120mm holesaw with a holesaw extender? Or you could make the extender from threaded bar.

 

[Inspector]

Mr. Monster. How are going to get the core out of the log with a hole saw? You’ll be able to cut a couple inches before bottoming out. Then everything inside that wasn’t cut with the hole saw will have to be chopped out. Followed by multiple drill and chop sessions until at depth. That’s a lot of work.

Pete

 

[Orraloon]

I think investing in blacksmithing some tooling like in the video if you want authentic. However a 120mm hole may be a bit much for most people to manage. I guess those guys had worked out what was manageable. Finding someone with the brawn and brains to carry it off is another matter. Looks like a bit of practice would be required.
As to machanical aid Amazon have a 4 5/8'' forstner bit. I don't know if they come any larger. With drill extensions, a serious big lathe to do it on and someone who really knows his way around as endgrain drilling usually wanders.
Cutting down the middle and scooping out may be the easy way to go.
The roman army was as much engineering and building as fighting and would have had a contraption for the job and plenty of grunt squaddies to turn the handle.
Regards
John

 

[Trainee neophyte]

https://www.irwin.com/tools/drill-bits/ ... -feed-bits

They claim 4-5/8" diameter as the biggest one. Not my area of expertise.

Don't you just need a really, really big spade bit? And a bucket of water to put out the fire from all the friction...

 

[ColeyS1]

It would depend on how accurate the hole needed to be, does it need to be super smooth with a flat bottom? Have you got loads to do or is it just the one hole?

Repeating what's been previously mentioned a 120mm hole saw then removing the innards with auger bits and a chisel is a slow but steady way of doing it. I made a toilet roll holder this way which was 3 holes 150mm ish diameter.

What's the hole for?

Sent from my SM-G960F using Tapatalk

 

[sunnybob]

I'm with Marcros.
Whatever you do will not be "historically accurate" so slice it on a band saw, use any number of methods of removing the trough, and stick it back together with a tough waterproof adhesive.

 

[owen]

Start off drilling with a 120mm holesaw as deep as you can. Then use a large auger bit to remove all the waste down to the depth you want to go. Then finish it all off with the holesaw.

 

[RogerS]

Thanks chaps...some good ideas there.

 

[xy mosian]

I think the split, trough and re glue has to be about the best solution.
Using any sort of holesaw or forstner bit is going to be difficult at 300mm deep. That is some extension. The other snag is that, for any sort of powered drilling, hand or machine, the wood has to be clamped to resist the turning forces.
Clog makers have used a sharpened spoon, well that's what it looks like, and go at it a little bit at a time. That way also has the advantage of being able to get a reasonable bottom surface.
xy