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Cutting a thick piece of steel

Does what it says on the tin
quelquod
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Cutting a thick piece of steel

#12032

Postby quelquod » December 5th, 2016, 12:31 pm

I need to cut a couple of sections of I-beam in situ to remove them. They used to be supporting elements of a building but now not needed. They are somewhere around 1/4" thick and about 4" each way. I want to do least damage to adjacent walls and ceilings.

I have a large and small angle grinder which I was thinking of using with a diamond blade. I have a couple of general purpose diamond blades which I've used for cutting slabs and tiles but I don't know how they'd perform or how safe they'd be on steel. I don't want to shell out for an expensive blade for 1 job if I don't really need to. Any advice?

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Re: Cutting a thick piece of steel

#12109

Postby martint123 » December 5th, 2016, 2:44 pm

I always thought diamond tipped tools like discs, drills etc were for use on stone/masonry and not metal. I may of course be wrong though.

1/4" thick by 4" - I think I would contemplate beg/borrow/hire a plasma cutter an angle grinder may make hard work of that.

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Re: Cutting a thick piece of steel

#12145

Postby bungeejumper » December 5th, 2016, 4:16 pm

I'm also doubtful that a diamond wheel would be any good on steel. Because of the slots in the disc it 'attacks' the surface in a way that's right for concrete but I don't think would be welcomed so much by a hard metal. But a metal disc has always worked for me.

There are, of course, (thicker) grinding and (thinner) cutting discs for metal, and TBH I've used both on quarter inch steel and cast iron. (Somehow I've never quite trusted the thin discs in some situations. But the thicker ones get hotter and are more likely to overstrain the motor if you're too keen.)

Either way, safety is a real issue, because you really don't want a disc shattering on you. Angle grinder discs have a best-before date, and for a reason. :o

BJ

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Re: Cutting a thick piece of steel

#12151

Postby csearle » December 5th, 2016, 4:26 pm

bungeejumper wrote:I'm also doubtful that a diamond wheel would be any good on steel.
BJ


I'm listening in with interest here because I've used the diamond disks (with slots) to take off several jammed padlocks in my time (and they are quite hard metal). I'm now wondering whether I was subjecting myself to an unacceptable amount danger.

Chris

quelquod
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Re: Cutting a thick piece of steel

#12223

Postby quelquod » December 5th, 2016, 6:31 pm

Thanks for the inputs.

Reason I thought it might be ok is that I've not had any difficulty cutting through reinforcement rods in concrete, not that they're as big a job as this but I've not noticed any jarring or juddering, just cut straight through. The smaller tile blade isn't segmented (don't know if it's got a special name) but I don't think the 4.5" grinder will be man enough.

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Re: Cutting a thick piece of steel

#12237

Postby bungeejumper » December 5th, 2016, 7:31 pm

Actually I think your 115mm grinder will probably do the job OK as long as it's got 800 watts or so in the motor. It just might take a little longer by the time you've built in a few breaks for cool-downs. And you might even find that the smaller disk gives you more flexibility when it comes to getting at the workpiece.

Each of your cross-cuts will be 12 inches, by my reckoning. (H shaped with 4 inch sides.) A 115mm disc ought to be able to last that long, so get a couple. Just don't buy cheapo-cheapo discs from Argos. Incidentally, the 'use-by' date is usually stamped somewhere on the metal collar. A reputable dealer won't sell you old stock.

BJ

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Re: Cutting a thick piece of steel

#12278

Postby bionichamster » December 5th, 2016, 9:33 pm

You can cut a structural I beam with a small angle grinder, I've seen it done. Just buy some metal cutting disks of standard 1mm thickness or thicker, not the ultra thin ones which will heat up too fast and wear down even faster! Don't try to do too much in one go (overheats the grinder and stresses/wears the disk), make sure you wear eye protection and preferably head/face protection as there's a good chance of breaking a disk.

Try and cut a long channel progressively deeper rather than trying to cut straight through in one spot, it's time consuming but works. You will go through a few blades, I've no idea how many (probably depends on technique and blade quality) once you've cut through the top and bottom faces you can plunge down and up into the vertical face as deep as possible then cut it on the side and hopefully you can join the two cuts up.

There's lots of info on t'internet on doing this (we looked it up before attempting).

BH

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Re: Cutting a thick piece of steel

#12312

Postby sg31 » December 5th, 2016, 11:01 pm

I've cut a fair number of steels much bigger than this using angle grinders. Usually the bigger the better.

Mostly they have been cut prior to installation, once installed access is the main problem, so you will have to use whatever you can get into the space available. Make sure you can get access all round the piece you want to cut or check that the disk will actually cut all the bits you need to. Sometimes if you have restricted access there will be a section the disc won't be able to get at.

Don't forget to use eye protection. The job can create a lot of sparks so make sure the work area is clear of anything likely to catch fire. Don't be too paranoid about this but best if you can have someone watching what is happening around you as you will need to concentrate on the grinder and work piece. If the area is very confined you might consider a mask. Other than that make sure there's ventilation.

I'm assuming you are removing parts of the beam and leaving some in place. If you are removing all of it there might be other options.

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Re: Cutting a thick piece of steel

#12360

Postby bungeejumper » December 6th, 2016, 7:59 am

Thanks for that, bh. This guy (www.youtube.com/watch?v=rM2SOWn5VI8) is using a 115mm grinder on a somewhat larger beam, and he finishes the first cut at 4.30. He's wearing a motorcycle helmet and visor, which I suppose is a good idea if you know someone who won't mind it getting singed. ;) I also have a few issues with the way he's (not) bracing his body for some of those cuts. YVMV.

BJ

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Re: Cutting a thick piece of steel

#12363

Postby quelquod » December 6th, 2016, 8:09 am

Thanks everyone, I'll have a go with the smaller grinder, it looks a bit of a job to manipulate the large one at ceiling height. Yes, it's in situ and cutting a large piece out as its not practical to get to the bolted ends or even manipulate the whole thing out anyway. I'll try some standard disks rather than my diamond one and see how it goes. I can't get all round the thing so might have a bit more cutting as a result.

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Re: Cutting a thick piece of steel

#13082

Postby 88V8 » December 7th, 2016, 6:56 pm

No problem with a metal cutting disc in a 4.5" grinder.
Mind you don't set the place alight.

V8

quelquod
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Re: Cutting a thick piece of steel

#13091

Postby quelquod » December 7th, 2016, 7:08 pm

I think the main thing to watch out for (aside from any cutting problems) is not to get in the way of the offcut - it looks rather hefty!

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Re: Cutting a thick piece of steel

#13782

Postby Hariseldon58 » December 9th, 2016, 6:39 pm

From an engineering background you will do fine using an abrasive wheel on steel, a larger grinder is easier to control than a smaller one.

Common sense, protect eyes and skin from hot sparks and be wary of the dust produced and avoid damage to surrounding equipment, metallic dust and grit from a grinding wheel is harmful to other equipment and the risk of fire to the surroundings.Set up a tarpaulin screen if you can.

Keep the motion of the wheel steady, in as straight a line as you can to avoid twisting the wheel, otherwise it will fracture, let the motion be steady easy progress, imagine a cutting disc as a series of minute sharp cutting edges, you want them to cut the steel and wear away, too much pressure you just crush and waste cutting edges causing waste of the cutting edges, too light a cutting force you tend to glaze up a disc and you get inefficient cutting.

The very thin discs are good for hardened steels. (Very fragile though !! Sometimes known as elastic wheels)

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Re: Cutting a thick piece of steel

#17110

Postby gadgetmind » December 21st, 2016, 9:24 am

Blimey, I've had an angle grinder for a couple of decades, maybe do 5-6 jobs a year with it, and it's still on the first disk. It is getting a bit small now though!

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Re: Cutting a thick piece of steel

#17140

Postby bungeejumper » December 21st, 2016, 10:08 am

gadgetmind wrote:Blimey, I've had an angle grinder for a couple of decades, maybe do 5-6 jobs a year with it, and it's still on the first disk. It is getting a bit small now though!


Dump your disks, and do it now. A new set with up-to-date datestamps will cost you a lot less than your first consultation with the surgeon. :|

I've had a steel cutting disk collapse on me, but fortunately it had the good manners to fold into two in a relatively refined and considerate way. And the guard caught all the flying flak. I've just noticed that the clown in the video I quoted earlier (www.youtube.com/watch?v=rM2SOWn5VI8) wasn't using a guard at all. Eek. :o

BJ

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Re: Cutting a thick piece of steel

#17182

Postby gadgetmind » December 21st, 2016, 11:47 am

The grinder seemed to have the usual guard so I guess you mean some additional guard?

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Re: Cutting a thick piece of steel

#23197

Postby quelquod » January 15th, 2017, 10:19 am

So as an update I did it yesterday using a 9" grinder and a couple of new blades as advised. Plenty of sparks! As expected it was quite a major problem to prop the beam up while I was cutting it and it was a bit of a 2-man struggle to shift it afterwards but the actual cutting was straightforwards from a desk built up on scaffold boards for the top cut. Sore on the old arms though.

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Re: Cutting a thick piece of steel

#23315

Postby csearle » January 15th, 2017, 7:06 pm

quelquod wrote:So as an update I did it yesterday using a 9" grinder and a couple of new blades as advised.
Excellent. Thanks for the update. C.


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