Me and my obsession with holes.

[shykitten55]

Hi all.

One of my projects has taken a turn and so I am needing to make a BIG hole in a piece of wood.

It is 5 ply. 300 x 700mm (give or take) and I need to make a 100mm (slightly bigger actually) hole in it.
I am getting some 100mm drain pipe (Plastic/PVC) and a flange (I am told it is called) so the flange is bolted to the plywood and allows the pipe to connect.

Once I get said flange, I will know the correct size hole.

Ok, it probably can be done with ......  a big drill to make a starting hole and a jigsaw going around the line.
But is there a nicer way?

[Mike Brown]

You either want to buy or build a circle jig. 

https://m.youtube.com/watch?v=bzs2FtKwC40

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[Paul Hutchison]

Up to about 200mm diameter I'd go for an adjustable hole cutter in a drill press (not sure if we have one at the space).

Ensure the cutting blades are sharp, clamp your work piece very well over some scrap ply, drill the centre hole then swap for the hole cutter and set the drill speed to as slow as you can (60rpm or so is good if you can go that slow). Keep hands, jewellery and clothing away and take it really slowly as these cutters can catch quickly and do a lot of damage.  Should cut a nice hole in fairly short order.

Paul

[Mike Brown]

For just a single hole you could see if anyone will lend you a 100mm Forstner bit. They are cleaner than a toothed hole cutter. 

I saw 100 and thought you were making a giant hole. 

[Patrick Barnes]

Your initial idea will work fine;
There's a compass on the shadow board.
There are some hole saws in the space, or Forster bits, or spade bits - that'll get you a starting hole.
Then jig saw as you suggested to get a rough approximation.

THEN I'd suggest the bobbin sander with one of the larger drums on it, to get a smooth hole out to the right size.
As long as you move the ply in the *opposite* direction to the drum (always move against a power tool's rotation) and stop now and then to check fit, it should be pretty easy.

-Patrick

[Patrick Barnes]

Oh, and for comparison, at least it's not this:

[Terry Dawson]

Patrick,

I need to this exact thing to get some handful of coaxial and cat6 cables up and out of a chimney.

How did you do this?

Terry

On 16 September 2016 at 12:18, Patrick Barnes <mrt...@gmail.com> wrote:

Oh, and for comparison, at least it's not this:

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[Patrick Barnes]

This is a 150mm hole, it's cut with a water cooled diamond hole saw. :-D

Before you can cut the big hole, you drill some smaller ones that the machine mounts to!

We paid a guy about $300 to do it. Considering Kennards charge $220 just for the hire it was a pretty good deal.

If you want a smaller hole there are cheaper options, 150mm is pretty big!

-Patrick

On Fri, 16 Sep 2016, 12:31 Terry Dawson <vk2...@gmail.com> wrote:

Patrick,

I need to this exact thing to get some handful of coaxial and cat6 cables up and out of a chimney.

How did you do this?

Terry

On 16 September 2016 at 12:18, Patrick Barnes <mrt...@gmail.com> wrote:

Oh, and for comparison, at least it's not this:

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