Best way to cut a perfect circle in steel?

[mikec]

Hi guys, just wondering on ideas on the best way to cut a decent circle in some steel, I'm making a stove from a calor gas bottle and what to cut a circle out of the top to BBQ but also want a cover to fit it too, basically like this stove below.

Normally I use bosch holesaws which aren't too bad to be honest but this probably needs to be 6-8" diameter. What process do I need to ask for plasma etc? Not sure I'm keen on oxy/propane as it never seems smooth. Any advice much appreciated cheers mike

[Soren Frimodt]

A plasma won't do it all smooth either. But you could use a plasma and then put in a lathe afterwards to making it perfectly round. If of course, you have access to these things

[mikec]

This is the thing, I'd have to pay for something so I want it to be pretty good, otherwise I might as well use my jigsaw again. Wasn't sure on how well plasma cut with regards to neatness. Cheers for the reply

[Bowie69]

Water-jet cutting is much neater than either oxy or plasma.

[TheRecklessEngineer]

Without machine cutting (Laser, water jet etc) a jigsaw is probably going to be neatest.

[Bowie69]

Starret do a 6" hole saw: 152mm / 6" Dual Pitch Professional Bi Metal Hole Saw

£51 though...

A gas bottle isn't that thick or especially hard, as above I think your best choice is likely to be a jigsaw in the end.

[nickwilliams]

Properly set up, plasma used with a circle jig will give you a cut which is at least as good as a hole saw.

If you are paying someone to do it, laser cut is probably going to give you the best cost/finish ratio, although CNC plasma will be cheaper and probably adequately tidy for your purposes.

[mikec]

I had thought of water cutting but didn't know how common it was, ill have a ring around, I only need it cutting into some sheet steel, which will be then welded on the bottle itself, cheers guys

[landroversforever]

If its in sheet rather than the bottle, I'd go waterjet personally .

[simonr]

Easiest for a nice job with basic tools is just to chain drill a circle of holes and use a die grinder or even a file to smooth out the jaggy bits.

Another option is to use one of the sideways cutting drills they sometimes advertise on TV. Homebase & B&Q sell them. Drill a hole in the middle and make an improvised compass to link your drill to the hole with a bar. Now the sideways cutting drill can only move in a circle!

Si

[muddy]

Unless your putting it in the Tate modern surely it doesn't need to be an exact circle? Could you not use a hole saw, jigsaw or series of holes and clean it up with a file as has been said?

In my experience of stoves and BBQ's once there is some fire rope, burnt sausage and soot involved the edges of things become slightly blurred.

Will.

[mikec]

Unless your putting it in the Tate modern surely it doesn't need to be an exact circle? Could you not use a hole saw, jigsaw or series of holes and clean it up with a file as has been said?

In my experience of stoves and BBQ's once there is some fire rope, burnt sausage and soot involved the edges of things become slightly blurred.

Will.

I was just after opinions really, I've had a look in screwfix since, and they have a six inch holesaw for 11 quid, should be ok for one hole. So ill see how that goes

[Troll Hunter]

As Muddy said, even without the effect of BBQ beer glasses!

[greenstream]

Hi

My personal choise would be to drill a small hole in the line of the circle and in the area where the hinge is going to be, the hinge will later on cover this hole. The drill have to be large enough for the Jigsawblade to enter.

Then use a Jigsaw to cut the circle.

I think this is the easiest way with basic tools.

Have been working on gac bottles before to make an oilheater (failed ;-) !) I killed a proff. powerdrill using a 85 mm. holesaw !

Cheers

Morten

[CwazyWabbit]

Good luck using a 6 inch holesaw slow enough and not burning out the drill. I'd think you'll want a slow running pillar drill to successfully make a hole with that. I'd go with chain drilling or a jigsaw

[studmuffin]

I bought a nibbler which fits onto any electric drill, for £25 + vat from a company called Accord Steel Cladding in the West mids.

Roofers use these to cut out circles in steel roof sheets where pipes are required.

Its very neat and accurate and you can cut pretty much any shape, although I have only used it so far on steel up to about 1.2mm.

Cheers

Barry

[moose]

Depends on what tools you have access to..

But i need to 2 8mm thick round plates for the end of my which drum project, did think about getting a laser cutters to do it for me but thought would give it a go first.

Did as Simon suggested and made a circle cutting guide for my plasma then just cut to circles out of plate.

The plasma did an ok job, but I made sure i cut the circles just oversized and turned them down perfect round on the lathe.

Or just make a square lid for the BBQ much easier

[vulcan bomber]

Or if you can get at a lathe just trepan one out.

[zim]

Cut it out a little bigger, using a grinder. Roundish, doeesn't have to be perfect.

Drill a hole in the middle so we can hold it in a chuck (or let me me do that) and then i can machine the outside round for you. I fly out to work on Sat, so will have to be one evening this week, won't take long to skim.

This is for the cover.

For the bottle, just cut it out with a grinder and then fettle it with a flap disc in a grinder to get it round. I'm not holding a calor bottle in my lathe LOL

G

Edit : Just reread your post, you wish to cut a hole in a piece of plate that you can weld to the top of the bottle. If so, this could fit in the lathe and we could bore the inside to be round. The maximum size i can hold is about 13" round or 13" diagonally if square.

[mikec]

Sorted this at the weekend, I bought the 6" holesaw but after using a three inch one it was obvious the drill would struggle, so I ended up using the jigsaw, its not perfect, but its not too bad. Hopefully I get a bit of let off in the rain so I can finish it off

[mikec]

Thanks for the offer Gordon