Holes

[DefTrap]

I need to cut some 100mm holes through a beam of approx 1800mm square (don't worry nothing structural). It needs to be fairly neat.
I don't have a drill press. I have a selection of hand drills - corded and cordless.
I've used holesaws before on smaller holes - they have their drawbacks when you exceed their depth , plus 100mm is rather more huge than I've tried before.

Ideas? Forstner bit in a hand drill?

[Mussels]

Thermite?

[Taff]

you don't say what material the beam is.

I drilled a 100mm hole through breeze block this summer using a diamond tipped hole saw and sds drill, the hole ended up neat enough, it is ever so slightly on the piss though.

[DefTrap]

you don't say what material the beam is.

Because i haven't decided yet.
I'll practice on pine, and if that works, I might try oak.

[Taff]

you don't say what material the beam is.

Because i haven't decided yet.
I'll practice on pine, and if that works, I might try oak.

so it's wood then, as opposed to concrete or steel, it makes a difference

how deep is the beam?

[DefTrap]

so it's wood then, as opposed to concrete or steel, it makes a difference

how deep is the beam?

It was wood in my head all along.

About 1800mm will be about right.

[bevvo]

You can still use a hole cutter - just chisel out the innards every time you bottom out...

[Taff]

You can still use a hole cutter - just chisel out the innards every time you bottom out...

that's what I was thinking, but you're only going to get about 200mm deep(at a guess) before the drill fouls and you can't get any deeper.

1.8 metre deep is one hell of a piece of wood

[Skub]

I need to cut some 100mm holes through a beam of approx 1800mm square (don't worry nothing structural). It needs to be fairly neat.
I don't have a drill press. I have a selection of hand drills - corded and cordless.
I've used holesaws before on smaller holes - they have their drawbacks when you exceed their depth , plus 100mm is rather more huge than I've tried before.

Ideas? Forstner bit in a hand drill?

If you don't fancy the holesaw option,you could mark out the 100mm hole and chain drill around the diameter with a smaller forstner bit,then tidy it up with a sander wheel. Less grabby than going full bore in one go.

[bevvo]

You can still use a hole cutter - just chisel out the innards every time you bottom out...

that's what I was thinking, but you're only going to get about 200mm deep(at a guess) before the drill fouls and you can't get any deeper.

1.8 metre deep is one hell of a piece of wood

Hmm. Maybe a sds chuck conversion and quite a few of these:

https://uk.milwaukeetool.eu/en-gb/sds-plus-extensions/

[DefTrap]

Fook sake - too many zeros. I meant 180mm.

[Silly Car]

180mm through timber is still going to be ‘fun’.

I’d use a holesaw but as follows:

Drill a pilot hole straight through the beam for arbor drill.
Drill max depth of holesaw* in from both sides
Drill a series of holes through beam (within 100mm hole) with 25/30mm spade / forstner bit from both sides to clear as much waste as possible.
Chisel out and drill from both sides with holesaw until complete.

The work piece should ideally be clamped to a workbench / drill press stand but we don’t live / work in an ideal world! Pilot hole should keep everything on the right path and drilling from both sides will get rid of break out.

*Reduce speed of drill and use side handle as well, because it’ll fuck your wrist if it ‘bites’ in to the timber.

[DefTrap]

Thanks chaps - I'll probably go with a hole saw first then as they're familiar enough and relatively cheap.

[demographic]

Fook sake - too many zeros. I meant 180mm.

Was just about to ask where you got the giant Sequoia beams from.
For 180mm depth of cut I reckon I'd just use a holesaw and chisel it out every time I bottomed it out.
I sometimes drill a couple of holes around where the cut is to help clear the waste out of the cut.
I reckon you'll mebbe get about 40mm depth per go, chisel it out and have another go.
If you can get to the other side you can dril a deep pilot hole with a very thin auger bit (I have them down to 6mm diameter which is about the size of the holesaws pilot bit.
Then you are going into the beam from both sides.

You can get long thin extensions to allow deeper holes to be done in stages with a holesaw.
Think forsner (spelling?) bits come in sizes upto about 76mm but its a big ask for a drill to do even that,
IIRC my Hitachi does upto about 76mm Forsner or so but thats a fair beast of a drill and not much smaller than a Milwaukee Hole Hawg beats it for power.
It will however power a 120mm diameter holesaw. Likely bigger but I've not needed to try it yet.

Oh, whilst Ive been posting this Silly Cars basically posted the same so erm... wot he sez.

[slowsider]

Thermite?

He doesn't want to blow the bluddy doors off.

Keeping the pilot hole true is going to be the hardest bit.

[Newey]

Weld a longer bar onto the hole saws mandrill.

[demographic]

Oh and just as a matter of interest, whats the hole for?
If its for a waste pipe I usually make the hole slightly bigger than the pipes external diameter because you never get the hole absolutely perfectly lined up and those big pipes are pretty rigid.
Bosch and Starett do holesaw extensions, think the one Ive used was a Bosch but it was a few years ago so I'm not sure.
Don't get an extension with an SDS fitment though cos most SDS drills have a torque limiting clutch which kicks in waaaay too soon and theyre shite for holesaw use above about 60mm.