How to drill big holes on a vessel ?

Perhaps using a big plasma cutter?

i

Thanks for the suggestion.I am wondering if there is a big drill machine which can be temporarily fixed to the vessel wall ?

Thanks again

300 is awfully big for any kind of hole saw or single point cutter not mounted on a fairly rigid machine. And if the surface is at all curved, good luck...

How about drilling a bunch of holes arounc the circumference and then connecting them with some sort of saw? Clean up with a grinder. Not fast, but will get the job done using widely available tools (probalby go through a few drillbits though)

Don't know much about them, but the plasma or flame cutting ideas sound worth looking into.

Thanks.That's how (small holes+grinder) we are making these holes these days. But as you mention, it is not fast. =DDnstead of drillbit a blade turning in this diameter perhaps would be helpfull.But I don't know who,where,how ?

Before you do anything to this tin-can, please advise what it is used for. With a 30 mm wall thickness is it perhaps used as a pressure vessel, ie. subjected to internal or possibly external pressure? If so, all bets are off regarding the cutting of ANY holes, unless they meet the requirements of the ASME Boiler & Pressure Vessel Code as to size and / or reinforcement requirements.

The ASME Code is a legal requirement in all US states and all provinces of Canada, also many foreign countries. Fooling around with pressure vessels is not something to do on the fly or by guess and by gum.

Wolfgang

If you want to do the torch route; Google "torch circle cutting guide" They have them for plasma cutters Princess auto (in Canada) has them for oxy/acetylene torches for $20.00

or, maybe build something along these lines;

THAT'd be a scary sucker to see in action

Thanks Wolfgang.For your information;Yes, these vessels are pressurized and sometimes are boilers.They are not subjected to ASME codes.I am not responsible for the whole production.Responsible just for searching a drilling method for these holes.

But it wont work.Because the surface is not perpandicular to the centerline of the hole.

30mm thick ?

Thanks in advance.

Selçuk SANCAK

How many holes? One? or 100? How much money can you spend? Oxy/acetylene torch or plasma seems to me to be the best bet. It would need to be a pretty good plasma to cut 30 mm thick material though. Drilling one hole that size is out of the question as far as I know. Hole saw would work with thin material, but 30 mm thick material kills the hole saw idea. Greg

The best method I know to cut heavy carbon steel is oxy-fuel torch. You could jury-rig a radius arm carrying the torch, by tack-welding the pivot block to the centre of the hole-to-be. By allowing the arm to pivot in a vertical plane you can maintain the torch-to-surface distance. Practice a couple of times on a scrap piece to get the motion speed right.....radial chalk marks help to set the pace, in conjunction with a second-hand clock.

If you have many holes to cut like this, purchase the appropriate equipment, which is a circular track held in place by magnets or tack welds, on which a self-propelled trolley carries the torch. In this case the radius arm points inward with the cutting torch on the inside end. Flexible tracks are also available to follow irregular or 3- dimensional contours. Again, practice on scrap and make set-up instructions to help speed-up the process the next time.

Wolfgang

P=2ES.: If it is a pressure vessel not subject to the ASME Code, to what code is the vessel built? Just curious.

O/A torch. Can you cut from the inside to blow the crap outward? A trick is to "draw" the circle for the hole (undersize) then make a series of center punch marks on it. Be sure to project the pattern "straight down" onto the surface, don't allow your pattern to bend with the surface or you'll never get a tube, for instance, to fit into the hole. The line will disappear but the marks won't. You'll need to grind the hole to size both for smoothness and to remove the flame hardened edge. Randy R

So the hole is not circular? Is the surface flat, or curved? Is it a compound curve?

We build tanks where I work although they are only 1/4 thick max. We are going to possibly be doing over 1/2 in. Now they cut holes by hand with plasma torch. Drilling isn't going to work, its not practicle, so forget it. We are going to start buring the holes before they are rolled with a CNC plasma cutting table. You asked for the best method. This is it. It sure ain't the cheapest but quality is going to be much better and much much more efficient. Outside of that the plasma circle cutter post is 2nd best idea Rosco,

30mm thick ?

Thanks in advance.

One thing that might work would be a diamond core drill. Often these are used for drilling large holes in concrete slabs, but the rig they use is portable and if you were to make a fixture to hold the rig perpendicular to the hole, you should get a nice clean hole.

Exocet.

John Martin

Brilliant :) Let me check if there is one in the warehouse.

Exocet would be fast.

Here is a more serious alternative: could you trepan it? Trepaning is commonly used to cut disks from glass sheets 300 mm diameter and 30 mm thick. The standard method would be to use a disk the size of the hole and attach a rim of harder material. (For glass a thin piece of steel will work. I do not know what I would recommend for cutting steel--perhaps it will not work because no materials are suitable.) Then one mounts it on the surface with a very slow drill and adds SiC slurry in water to do the actual cutting. The cutting is done by grinding and the cutting rim wears away and can be replaced as needed. The power requirements are low, but you would need to firmly mount your drill press. On glass you might use 50-100 rpm. It leaves a nice round hole. This method would work on a curved surface.

Another simple hole cutting idea that will probably cause bodily injury on your project is a router with a carbide bit and a good hole cutting attachment. It works great for cutting 15 mm Al disks. It is fast, noisy and scary.

Scott