Large shallow metal bowl

[anaminal]

since everyone was so helpful with my last question... thought I'd raise something a little trickier!

I've been asked to produce shields for my club - spec is 1mm thick steel, in a domed shape of 55cm diameter, 10cm vault, and a rolled edge. I produced one out of a metal tray and a few hours of hammering against a tree stump - but I want to make a batch and have them all consistent (and not looking like they've been made by a guy hammering it out against a tree stump).

I contacted quite a few metal pressing fabricators but they all came back with crazy costs, a few recommended I speak to metal spinners, but a few early quotes from these guys are coming back equally expensive also. Any ideas where I can have something like this produced?

pic attached showing side profile what I'm after. any thoughts or comments welcome!


Cheers,
Chris

 

[TFrench]

I have a feeling graduate owner on here uses one of his lathes for metal spinning. Would it not be worth looking into fibreglass instead? Not historically accurate, but a lot easier and cheaper.

 

[sunnybob]

The reason the metal spinning (and machine shop) price is so high that a shape like that has to have a mould to press (spin) the metal to.
making even a simple mould like that takes a skilled engineer at least a day.

How much would you pay a skilled engineer for a days pay and use of his workshop?
the metal is pennies, a skilled spinner could make it for about 50 pence, but that mould is where all the money is.

A hobbyist is the only way you'll get those at a small cost.

 

[novocaine]

that could be hydroformed but it wouldn't be easy in 18 gauge steel. basically you trap the sheet between 2 thick sheets one with a hole in then inflate it with water (ok there's a bit more to it than that). still not easy though. the problem would still be getting your out radius right.

as bob said, in an industrial world, that would really need to be pressed, which means 2 very big bits of metal at an massive cost, followed by some very careful machine work to make a matching pair then a 10 ton (minimum) press to form the blank. that's a rather large outlay to make shields.
even a metal spinner is going to have a hard time with it because of the change in shape, he'd need a former to roll the end.

you could get better at using your hammer and tree stump of course. carve out the inner and outer actual shape then peen the first pass on the inner, then flip it and use outer and a bigger hammer to start smoothing, a few passes is usually enough to remove most of the ripple. it's a shield, call it patina.


1 last suggestion that isn't what you asked by might get you out a bind. vacuum formed plastic and some care taken to make it look like metal, which is how most prop stores would do it for a movie and such.

 

[sunnybob]

find out where other clubs get theirs from. Or get a few clubs to band together to make a bulk order.
Once the mould is made, the price per item is minimal for a metal spinner.

(I used to work for a small metal spinning company, i know whereof I speak)

 

[AJB Temple]

Surely if these are shields to recreate old weapons, they would have been hand made and somewhat irregular. Then battle scarred. is consistency what you really want?

 

[sunnybob]

Its much easier to bash dents into a new shield than it is make an individual smooth one.

 

[anaminal]

I think Novocaine's suggestion of hammering and flipping might be the way to go - so far no one has come back with a quote I (or anyone I train with) could afford.

I'd prefer not to use use fibreglass as they will actually be used as shields - light contact, but all the same, steel will last as long as most people will train, whereas fibreglass will degrade over time with all the impacts.

I suppose this is me being picky, but I'd just prefer it not to be made of plastic. I'm aiming for both tradition and function - so it has to be useful, but also approximately historically accurate. Plastic just puts me off

Sunnybob you make a good point, there's no use worrying too much about the finish as they will inevitably become damaged over time anyway... so I think I might get the hammer moving this evening and see how long it takes me to make them once I get into the swing of it...

Cheers All
Chris

 

[novocaine]

remember, little hits lots of times rather than big hits a few times. the only time you want to hit it hard is on sharp shapes, none of yours count so take it easy.

they used to say that good practice was to swing a hammer twice the weight for a week before you start doing this sort of stuff. so I use a toffee hammer.

good luck, it can be quite rewarding.