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mains powered drill for a very big hole saw (7 inch)


magnetman

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I am fitting opening portholes to the side of the hull below the side decks on my barge. Its OK its a modern boat so I am nor ruining a hystoric vessel... and they are 18 inches (450mm) above water and proper heavy ship portholes.

 

Anyway the way I am doing it is cutting a 7 inch hole (177mm) in a 2 inch (50mm) thick piece of mahogany then cutting the same hole in the 6mm (1/4 inch) hull side then bolting the porthole to the piece of wood then to the hull. This recesses the porthole a bit To prevent damage and hopefully avoids condensation problems associated with welded in portholes or those directly bolted to the hull.

 

Anyway I have done one and virtually destroyed my 14.4v (old) makita drill. A second one I did with jigsaw was far less tidy.

 

So is there a 240v drill which can handle this? Slow speed thing with heavy duty gearbox and motor. Ideally I will be doing 3 more holes in thick mahogany and 3 more holes in the steel all with the 7 inch ( 177mm) holesaw. I can do the steel with a jigsaw but the holesaw is much more accurate and tidy specially on the wood.

 

Any drill recommendations?

 

I do not want to flame cut the steel as I am cutting round holes in the existing lining and insulation just big enough to slot the porthole/wooden ring into and the two I have completed are excellent.

 

I know there is the option to get deep spigot portholes but they are a bit tricky to find and £££

Edited by magnetman
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Hmm.

 

They can, but the ones that do are designed for boring the Channel Tunnel looking at sizes. The low power ones might only manage up to a 2" hole due to the mount getting in the way.

 

Probably wouldn't clamp to the mahogany too well either ;)

 

If you managed jitter OK with the handheld battery drill, just about any decent mains drill will do.

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Maybe. But the speed for a holesaw that big on mild steel is 50rpm. I wonder if the core drill would have enough torque at that rpm ? Need a very slow machine really.

 

I think Bizzard said a while ago there was an old 'Wolf' drill which would do it?

 

Eta I have used a 'decent mains drill' and it started smoking immediately there was any load on it :rolleyes:

Edited by magnetman
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Looks like your problem is solved - aha - a matter of distance.

Isn't the Hilti something you could hire from somewhere more local to you.

 

Thinks - you said drilling a hole in the steel wasn't the challenge it was the teak inlay and jig saw combination so -

what about jig saw to rough cut and finish off with a plunge router to give you a fine finish??

If so, t'would be best to make a template for the router to follow or an arm around which to push the router around. A small router would do as it's for the finishing cut.

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Kind offer I do appreciate it but I think drilling steel is different to stones.

 

I have done the drilling a ring of holes thing several times for chimney collars and its a bit untidy really.

 

I have been advised it is feasible to do this with slitting discs by someone who has done it. Perhaps I should try it. With face shield.

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Thanks for the offer :cheers:

Am in London so a bit far away - do you have a model number as I am open to the option of buying a decent drill for this if it isn't silly money :)

 

Edit to rearrange a bit

Edited by magnetman
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Kind offer I do appreciate it but I think drilling steel is different to stones.

I have done the drilling a ring of holes thing several times for chimney collars and its a bit untidy really.

I have been advised it is feasible to do this with slitting discs by someone who has done it. Perhaps I should try it. With face shield.

the reinforcing steels in the concrete of the vault wall never stopped it, if your going to attempt with a disc may I suggest practice on a piece of scrap first, because I find it hard to see how a straight disc can cut a round hole, can you not whip into a boatyard that has a plasma cutter, bet they would do it for a beer if you ask nicely. Should write faster Edited by craftycarper
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I know a plasma cutter is the thing to use but I prefer to avoid burning really

A plasma cutter is not burning in the same way that a gas-axe is, if set correctly it will only just pentrate the steel causing no damage inside.
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I do have a man on a boat with plasma cutter who will take beer as payment as all welders do but as already mentioned I am not keen on burning it due to the lining and wanting to do a relatively "surgical" job also not being in a particular hurry :)

 

A round hole can be done but the disc does flex more than most people would be happy with.

A plasma cutter is not burning in the same way that a gas-axe is, if set correctly it will only just pentrate the steel causing no damage inside.

OK

I talked to a friend who has one and he seemed to imply it was slightly invasive but then I was talking about doing it from the inside so maybe I misunderstood him. Have never seen one in action :)

Edited by magnetman
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Thanks for the offer cheers.gif

Am in London so a bit far away - do you have a model number as I am open to the option of buying a decent drill for this if it isn't silly money smile.png

 

Edit to rearrange a bit

It's an old Wolf, so not available now!

I could get it to Chessington on Saturday if that's any good to you.

 

Richard

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