Mandrel droop

[Bumpy Beads]

So there I was, experimenting with terra this afternoon, and actually getting a little bit of colour out of it for a change.... when all of a sudden....... my mandrel drooped about an inch to the left of my bead.... and then snapped off and landed on my table with my bead on it!!! So what's that all about then?! 

Did I overcook it? Or maybe it'd got weak from when I'd gripped it with the pliers? Or is it the beginning on a Mandrel Droop Pandemic?!?!??

You heard it here first...

[♥♥Tan♥♥]

Just got too hot Petal.......keep an eye on it in future because sometimes they can snap the other end and the whole molten lot rolls at you....try to keep the heat just on the bead

[Bumpy Beads]

Phew, thanks Tan. What a relief. I had visions of official government people wearing white paper suits and wellingtons sealing off my home and seizing my mandrels for "testing".

[♥♥Tan♥♥]

HEHE I've done it myself when I've been concentrating on the bead too much and not the whole thing, then all of a sudden you think 'Ello, thats gone a funny angle, then it falls on you....its ok when its the outside end....the first big bead I tried to make...on a thin mandrel I should add.....I manged to melt the whole thing including the mandrel.....luckily it fell on the worksurface......you do it once........

[Trudi]

Ohh could turn nasty!

[BeadyBugs]

I've done that too - it chafed!

2 cat's feet on one spindly mandrel, one stayed put, one tried to run off across my table.

HP x

[♥♥Tan♥♥]

hehehe I can see it now

[stuwaudby]

Prepare for engineering!

Repeated heating of stainless steel de-crystallises the metal and drives the carbon out of the metal matrix. This means it turns it back to iron, which is much weaker and has a lower melting point. Iron melts at 1260 DegC and Stainless steel at 1363 - 1464 DegC. Your flame is well above all these temperatures. Well used mandrels will be weaker and melt more easily.

The bead release insulates the mandrel which limits the amount of heat passed through to the steel. So long as the heat is conducted away from the work area faster than it enters thorugh the bead release your mandrel won't melt. Thicker mandrels conduct more heat so are more heat resistant. Dont skimp too much on your bead release - it's protecting your mandrel as well as releasing the bead.

Your mandrel probably broke because it was being heated directly by your flame or radiation from the bead in a potition unprotected by bead release.

Personally I snip of the end of my mandrels when they become too soft. It's usually obvious when removing a bead.

What we really need is tungston mandrels - which wouldn't melt till 3000 DegC.

[garishglobes]

That post took me straight back to the metallurgy labs!  Low carbon steels and eutectic points, anyone?

I'm sure I've seen tungsten mandrels in the past, but I think they were said to be brittle. Might be dreaming, though!

[Trudi]

Funnily enough I was at Angie's house on Sunday and we (I say we - it was Di) was making a bead directly onto tungsten (no bead release). The bead did come off the mandrel, but you have to do it hot - and lordy you wouldn't find me doing that!