Potje Firebasket? Drilling cast iron?

[DrPhill]

I have a 'potje' like the one above (max outside diameter about ten inches). It is intended as a cooking implement - perhaps it stands in the embers? We are never likely to cook enough to use it as a cooking vessel, nor would we wish to burn enough wood to do so. But I wonder if it would make a good 'fire basket'. Standing off the ground it would reduce the damage to the soil. It is made of cast iron - is this a suitable material for a fire basket? It will need some air inlet holes, which I will need to drill (freehand). How difficult/feasible would this be? Am I likely to crack the cast iron if I drill too close together? Am I mad for considering doing this?

Any and all thoughts appreciated .

Thanks

Phill

 

[Spectric]

It may well crack if you put a fire inside it but you won't know until you have tried. Cast iron drills ok, slow speed and maybe a hole cutter which will saw a hole rather than drill.

 

[MARK.B.]

I may be wrong in my thinking but i would think that at 10" it would be far to small to give out any kind of useful heat

 

[Richard_C]

Put it outside as it is, put loosely scrunched balls of old newspaper inside - or today's daily express before you read it - and a few bits of wood (offcuts, twigs, anything), light it and see what happens. Lots of the ones you see in shops don't have airholes. Fire burns, heat rises from middle, air gets drawn in round edges. 10 inch is a bit small but should work.

 

[AES]

Don't know anything at all about fire baskets, etc, so I don't know where you want any holes (rim, sides, bottom, etc).

But although it's quite a "big thought", in practice, drilling cast iron is very easy.

Sharp drill, moderate feed pressure, low speed (rpm) and plenty of lube (anything "wet" will do). Although people will tell you that CI is generally self-lubricating (and it usually is), the potential problem is that poor casting techniques in such a - probably low quality - item often leads to both inclusions (bits of carbon slag and/or even casting sand stuck in the mix as it cools) and/or air bubbles. Hence the lube (carbon slag is generally VERY hard). Also, because of possible slag and/or bubbles, I wouldn't drill the holes too close together, nor on exactly the same line. By that I mean that if you want a line of holes all the way round the sides (for example) don't drill the holes at exactly the same distance apart, nor on exactly the same circumferential line (let them vary up and down a little). Again I know NOTHING about your intended usage, but in the above I'm assuming holes of at least 10mm dia.

Re a post above, personally I would NOT try a hole saw as suggested above. Why? I assume the surface to be drilled will not be flat but some sort of curve? Rpm likely to be too high.

Incidentally, depending on hole diameter, it's by no means impossible to drill CI with a hand/breast drill ("egg whip"). I've done it myself several times, just takes a bit more time, that's all.

Basic approach? "Drilling CI is a lot simpler than it appears if you're just thinking about it"!

HTH

 

[DrPhill]

I may be wrong in my thinking but i would think that at 10" it would be far to small to give out any kind of useful heat

It is almost certainly too small to warm people.... I was not clear. I intend to use it for cooking on rather than keeping warm. The potje is too heavy to be worth carrying outside the garden (for camping and other trips), so if I am cold I will go indoors. I was looking at kelly-kettles and hobo-stoves - we always have lots of small bits of wood left over when we get a log delivery and I was thinking about cooking without gas or electricity.

 

[DrPhill]

Given that it would take me quite a while to drill enough holes, I might try just making a fire in it to see if it cracks/smokes etc. But I think that I will wait until this dry weather is over.

Sharp drill, moderate feed pressure, low speed (rpm) and plenty of lube (anything "wet" will do). Although people will tell you that CI is generally self-lubricating (and it usually is), the potential problem is that poor casting techniques in such a - probably low quality - item often leads to both inclusions (bits of carbon slag and/or even casting sand stuck in the mix as it cools) and/or air bubbles. Hence the lube (carbon slag is generally VERY hard). Also, because of possible slag and/or bubbles, I wouldn't drill the holes too close together, nor on exactly the same line. By that I mean that if you want a line of holes all the way round the sides (for example) don't drill the holes at exactly the same distance apart, nor on exactly the same circumferential line (let them vary up and down a little). Again I know NOTHING about your intended usage, but in the above I'm assuming holes of at least 10mm dia.

Really goo advice - thanks AES

 

[Richard_C]

, I might try just making a fire in it to see if it cracks/smokes etc

And to test out the cooking bit, don't go spending money. Try it first with the grid off your grill pan from the kitchen. Cast hibachi bbqs don't have airholes, but they are a bit shallower. Rock lined dug out fire puts don't have air holes. I expect it will crackle to start with but you normally cook over embers etc so give it a go.

 

[AES]

Given that it would take me quite a while to drill enough holes, I might try just making a fire in it to see if it cracks/smokes etc. But I think that I will wait until this dry weather is over.


Really goo advice - thanks AES

No problem Dr. Phill. One small point I forgot, if you do go ahead with drilling holes. If you've drilled ordinary mild steel, or ali before, (or even wood sometimes!) you'll be used seeing quite long spirals of waste coming off the drill (swarf). You won't see that with CI. What looks like fine black & slightly lumpy "sand" is perfectly normal swarf when drilling CI. (Forgive me if I'm teaching granny to suck eggs here)!

And BTW, if you do end up drilling holes, don't expect it to take over long. It goes reasonably quickly actually, even with a hand drill (IF the drill bit is sharp).

 

[DrPhill]

Forgive me if I'm teaching granny to suck eggs here

Forgiven, you are telling me stuff I don't know, for which I am grateful. And even if I knew it, I would not mind - never harms to be told twice, and not every reader of the forum would know so it is not just me you are telling.

 

[Old.bodger]

Just to correct a previous post. NO lubrication when drilling cast iron.

 

[Droogs]

Before you drill it at least try making potjiekos, oxtail or beef and beer are my favourites. Oh and remember you never never ever stir once you put it on the coals

 

[DrPhill]

Before you drill it at least try making potjiekos, oxtail or beef and beer are my favourites. Oh and remember you never never ever stir once you put it on the coals

Since I do not eat meat, I will give that a miss..... thanks anyway. My first plan will be to try a fire in the pot without drilling - it may work....

 

[Tris]

If you have looked at hobo stoves and enjoy tinkering, why not take it another step? Then you can use the potje on top

https://www.instructables.com/rocket-stove-2-3/

 

[Stevekane]

And to test out the cooking bit, don't go spending money. Try it first with the grid off your grill pan from the kitchen. Cast hibachi bbqs don't have airholes, but they are a bit shallower. Rock lined dug out fire puts don't have air holes. I expect it will crackle to start with but you normally cook over embers etc so give it a go.

Hibachi cast iron BBQs, theres a blast from the past! I used one a lot and it was a crappy contraption that wouldnt burn a sausage untill I drilled a few holes in the bottom and made a grate from some bits of that perforated steel like mini cable tray,,then it was a great little BBQ, and if Im not mistaken Im sure I recall seeing Hibachis with a couple of little tin shutters fixed to the front?
I think you need air under the fire for it to work well.
PS, your not going to cook Hedgehogs in that pot are you?
Steve.

 

[Limey Lurker]

I'd cut radial slots on the lower third with an angle grinder.

 

[Gazbo]

I have a 'potje' like the one above (max outside diameter about ten inches). It is intended as a cooking implement - perhaps it stands in the embers? We are never likely to cook enough to use it as a cooking vessel, nor would we wish to burn enough wood to do so. But I wonder if it would make a good 'fire basket'. Standing off the ground it would reduce the damage to the soil. It is made of cast iron - is this a suitable material for a fire basket? It will need some air inlet holes, which I will need to drill (freehand). How difficult/feasible would this be? Am I likely to crack the cast iron if I drill too close together? Am I mad for considering doing this?

Any and all thoughts appreciated .

Thanks

Phill

As Richard C stated, heat rising from the middle, cooler air drawn in down the sides
This aides in cooling the sides, (That's how gas turbine blades are cooled, called boundary layer cooling.) and if not too tightly packed, can make the burning as efficient as a draught from underneath. ( plus the ash doesnt fall out of the bottom.) It shouldn't crack, so long as there are no sudden temp changes, such as sudden lighting one side first with petrol, or a blowtorch, or chucking water on it whilst still hot. "Gently heat, gently cool" with cast. If it cracks then, chances are it had existing flaws in the material.
Worth trying before drilling anyway.

 

[Stevekane]

As Richard C stated, heat rising from the middle, cooler air drawn in down the sides
This aides in cooling the sides, (That's how gas turbine blades are cooled, called boundary layer cooling.) and if not too tightly packed, can make the burning as efficient as a draught from underneath. ( plus the ash doesnt fall out of the bottom.) It shouldn't crack, so long as there are no sudden temp changes, such as sudden lighting one side first with petrol, or a blowtorch, or chucking water on it whilst still hot. "Gently heat, gently cool" with cast. If it cracks then, chances are it had existing flaws in the material.
Worth trying before drilling anyway.

Maybe I had my sausages packed in too tightly and they were impeding the inward airflow,,would it be worth drilling holes in the burgers to creat a venturi effect,,
BTW intresting stuff about the turbine blades.
Steve.

 

[Gazbo]

Maybe I had my sausages packed in too tightly and they were impeding the inward airflow,,would it be worth drilling holes in the burgers to creat a venturi effect,,
BTW intresting stuff about the turbine blades.
Steve.

Thanks Steve. I think Rolls Royce Derby came up with the concept, but don't quote me on that.
They beed high pressure air from the compressor section, down the hollow turbine shaft, back towards the turbine blades. The blades themselves are perforated with tiny holes. This compressor air ( still pretty hot from the compression cycle) provides a thin wall of relatively cool (hot, but much cooler than the actual exhaust gasses) air, which is sent back into the main gas stream, through the patterns of blade- holes, to flow over the blade surfaces, which works a bit like a thermal blanket of air, effectively seperating the blades from the main superheated gasses, hence keeping the blade temps lower than would otherwise have been. I believe a similar system is incorporated within areas of the engine casings too for the same reason. So the actual hot stuff is channelled, like jam in a butty, in theory never really touching the sides.Not cold, but much cooler than would otherwise have been. There ya go. Crash course in GT tech. Lol

 

[AES]

Just to correct a previous post. NO lubrication when drilling cast iron.

Would normally agree 100%, but assuming this is a cheapo/low quality casting, there will almost certainly be inclusions. They are hard enough to take the edge of almost any drill, hence the need for some sort of lube. Water will do at a pinch - been there, done that (NO T shirt though)!