Cutting tool that causes few sparks/shavings? 1

[hringm]

I have a project where I need to find a portable cutting tool and it has been difficult for me to find what my boss wants me to get. The tool needs to do the following:

- Cut through steel, up to 5/8" thick
- Cut holes up to 12" in diameter
- Cause no sparks, or very few
- Create no metal shavings, or keep them contained

I thought shear cutting might work since there's no sparks and very little shavings, but that doesn't seem to work for 5/8" thick metal. I also have looked into water-jet cutting, but it would produce water and metal shavings that would be difficult to contain.

Does anyone have any recommendations of tools or cutting methods I should look into? Thank you for your help.

 

[tomwalz]

As an example, you want to cut 12" round holes in flat, mild steel plate that is 5/8" thick?

How many holes?
In the shop or in the field?
You do it or sub it out?
Why no sparks? Risk of explosion?
Does "no sparks" also mean a low temperature.
Is "time to cut" important? Does the boss care how fast the holes are cut?
Can you cool with water?
How important is "no metal chips"?
Can you use a vacuum pick up for chip collection?
How important is cut quality as in hole size and shape?
How important is cut quality as in condition of the edges of the hole?



Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.

 

[TomDOT]

Waterjet cutter with a capture trough under the workpiece. There are portable versions available. Meets all the stated criteria. Trough solves the containment issue. Typically the trough starts out partially filled with water to disperse the (remaining) force of the jet.

 

[hringm]

Tomwalz, the tool is needed to cut holes into transformers. And to answer your questions:

How many holes? The tool wouldn't be needed often, just for special cases. Just one hole per transformer, maybe 15-20 times a year.
In the shop or in the field? It will be in the field, since the transformer is already in place.
You do it or sub it out? My boss would like for us to buy a tool for ourselves. But if I found a service or a rental or something like that that would be best, I would look into that and recommend it if it was best.
Why no sparks? Risk of explosion? No sparks because we are cutting into a transformer.
Does "no sparks" also mean a low temperature. Yes, low temperature would be best.
Is "time to cut" important? Does the boss care how fast the holes are cut? Time to cut is not important. The hole doesn't need to be cut quickly.
Can you cool with water? I think cooling with water would be okay, as long as water doesn't go into the transformer.
How important is "no metal chips"? Metal chips can be made, as long as they don't fall into the hole made into the transformer. Maybe this is an impossible requirement, but I'm trying to gather all the information I can.
Can you use a vacuum pick up for chip collection? A vacuum pick up would be fine.
How important is cut quality as in hole size and shape? Not extremely important, the other criteria is much more important.
How important is cut quality as in condition of the edges of the hole? Same, not extremely important.

TomDOT, I have looked into a portable water jet cutting system. But as far as I can tell, water and metal cuttings would go into cut hole and therefore into the transformer, which is what my boss doesn't want.

I realize that this has a lot of difficult requirements, which is why I've been having trouble. So I very much appreciate any advice anyone has.

 

[MikeHalloran]

Ah. Not fouling the transformer interior with chips or water amounts to another restriction; the cut must be made from one side, or mostly so.

Now, how to do it.
What comes to mind is a holesaw, but you need an extraordinary size.

Instead, i'd try drilling and tapping a blind center hole (not all the way through), screwing on some sort of pivot stud, and using a trepanning tool on a long bar to cut through. (Think of a holesaw with one tooth.) Driven manually, or with a powerhead from something like a big pipe threading tool.



Mike Halloran
Pembroke Pines, FL, USA

 

[TomDOT]

Ah, keeping cuttings and water outside of a container you're cutting is a different kettle of fish. Sounds like MikeH has a good approach, if you're only doing 1-2 per month.

 

[hringm]

Mike, thank you for the idea. That sounds like it could work. I will into that.

 

[mfgenggear]

Is there enough room between the transformer & wall of the exterior enclosure, so that a shield can be installed between.
leave a small gap in between to clear any tooling.
then duct tape any open spaces. then use standard cutting equipment. such as a plasma cutter, or hole saw as Mike suggested.
then use a shop vac to suck up any particles. It's low tech but may work.
use sheet material that is cheap & light to use. & that may be reused or thrown away.

It is not an easy task to ensure, no debris flings into the transformer.

Mfgenggear

 

[berkshire]

Is this transformer going to have oil in it, or can you drain the transformer before you cut?
As suggested by others a fly cutter or trepanning tool, Or a milling cutter in a drill motor on the end of the Radius bar.
I would not suggest the use of a plasma torch, I have first hand experience of nearly being deafened and a shop filled with light blue smoke, after trying to cut a transformer housing with a torch. ( it was not as cleaned out as they said it was.).Luckily the case held together.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[arunmrao]

Berkshire,

I can well imagine the trauma,as I have had a similar experience. In fact, I am wondering the need to undertake such a risk filled task.

Last month I faced,our 33kv/11kv, 5 MVA transformer insulation failure. I would not like anyone to experience that.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[ajack1]

I am not sure how practical it would be to manual trepan a hole of that size through 5/8 plate.
I would have though a better option might be to fix a plate via a tapped hole or two and use a router, you should be able to leave a very thin wall and clear out all debris and then just punch out the disk.

 

[ornerynorsk]

My though is to do it properly from the start. Have a casing made with the correct hole in it, and swap the innards. Never been up close and personal to large transformers, so I don't know if this is a practical approach, either.

Having in excess of 30 years in the machine shop, my only other suggestion would be a portable milling machine bolted onto the housing, and cutting almost through, then taking a metal cutting chisel and shearing the remaining web to remove the knockout, ala can-opener style.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[hringm]

Thank you everyone for the ideas. I'm not terribly familiar with machining and cutting so just having the right key words to search will help a lot. I think the plasma cutter is right out. I will look into the fly cutter, trepanning tool, and router.

Ornerynorsk, sometimes we get work with brand new transformers in which case they can have a hole done in them correctly and a new tool is not needed. This tool is needed for the rare special cases where we are on an old transformer that is already in the field and needs a new hole in it. But thank you for the can-opener idea. It's certainly not one I would have thought of, and I'll keep that possibility in mind.

 

[mfgenggear]

Yes I agree if the transformer has oil in it will be dangerous, with any tool.
the reason for oil is to cool the transformer.
I assumed that since a hole was being machined, no oil was present. and was not the containment
that was being breached. I guess that question should have been asked?
Thanks for pointing that out.
I actually like the suggestion to replace the transformer. there job done.
no danger of any disaster.

Mfgenggear

 

[tomwalz]

Wouldn't it be faster to just swap transformers? I am assuming you won't work on them live so downtime is a real issue.

We get pretty unhappy when the power goes out and everyone stands around. Fun for a while then pretty boring and expensive.

Tom

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.

 

[TomDOT]

Swapping transformers certainly sounds like a better plan to me.

Another thought - are any of these "old" transformers old enough to be PCB-filled?

 

[hringm]

Swapping transformers would probably be the best plan, rather than cutting a hole in one. But my project is to find a tool that can cut a hole, so I have to find out the best way to do that.

 

[BillPSU]

You are asking how to cut a hole in .625 plate. In the normal fabrication processes the hole would be created using some flame process such as plasma, oxy-acetylene or oxy-fuel cutting process. For extreme cases a waterjet with abrasive injection could be possible. Since none of these processes appear to meet you requirements some form of machining will need to be looked at. A 12 inch hole saw, a twelve inch trepan tool or some form of a drill-mill combination process. All of these processes would require some type of chip control such a vacuum collection process. All of these process require bringing a machine with substantial horsepower.

My suggestion would be to utilize a digger derrick removing the standard auger and use some sort of a custom auger/trepan tool. The design of the tool will be difficult and will require special attachment details to clamp the new trepan tool against the transformer.

How about buying transformers with twelve inch holes with inspection cover plates?