[TheForge] chip shapes and materials

[Jerry Frost]

From: "Bruce Freeman" <freemab222 at yahoo.com>


> Frosty,
> Your idea on thermally conductive chips is excellent.
> What we need is small (maybe 3/4" dia) balls of a
> highly refractory and thermally conductive material.
> Frankly, I'd be inclined to try commerical alumina
> spheres first.  Failing that, then hand-rolled
> rrammable refractory spheres.
>

I don't expect to find an ideal material except by shear luck. Commercial 
castable/rammable high alumina refractory is available but 55lbs is about 
$185 + shipping so I may shop for an alternative. Then again, maybe I'll hit 
a lottery!

> But since such refractories are inherently not very
> conductive, how about going back to the "rice in
> porcelain" idea.  Take a wooden bead, 1/2" dia.  Wrap
> it in castable refractory about 1/8" thick, making a
> ball about 3/4" dia.  Push a punch though the bead
> hole to clear away the "clay" at that point.  Let it
> set, then fire it - burning out the wooden bead.
>
> Voila', a hollow refractory sphere.  Being hollow, it
> would not "store" heat in the thermally inaccessible
> center.  (This is roughly equivalent to having a high
> thermal conductivity.)  Being roughly spherical, it
> would be fairly strong, despite being hollow.
> Furthermore, the holes would allow heating from the
> interior to some degree, for what that's worth.
>
> Sounds like a fair amount of trouble to go through,
> but talk is cheap!
>

My alternative for making hollow sphere's is tagged to Andy's reply. and 
yeah, talking about this stuff doesn't cost much though I prefer to think of 
it as economical. <grin>

> BTW, I disagree about the torus (lifesaver) shape.
> Such shapes are used for distillation columns.  They
> pack quite tightly, and I think it would be tough
> working with them.   Go get a gross of lifesavers and
> give it a try :^)
>

Packing and keying together are two entirely different things. An 
unconsolidated media may be compacted to it's maximum density and not be 
mechanically competent, (structurally rigid) beach sand is a good example. 
While some materials can be at a small percent of compaction and be locked 
up like a bag of jacks. Crushed sand is a good example, you can pour it 
loose and just vibrate it a little and it'll set up like concrete, walk on 
it without leaving a print. Take a compactor to it though and you may get 
another 30-50% compaction. The difference is the sharp broken particles key 
together forming interlocking bridge structures. Rounded particles on the 
other hand will almost automatically settle to maximum compaction but slide 
off each other so there is little if any structural bridging. A bag of 
marbles in other words.

Of course I may be wrong but I think toroids will remain loose enough to 
work fine, certainly looser than the broken Chips used in commercial forges.

> I'm also intrigued by the idea of using carbon for the
> chip.  Sure it would burn, but probably not very much.
> Graphite crucibles are practical, and they take much
> more stress than these chips would have to.  I'm still
> thinking of "marbles" made out of commercial (tough!)
> coke.  Unfortunately, this stuff seems to be available
> only in large (fist sized) chunks, and breaking it
> apart is no simple trick.  Maybe use a hole saw on the
> stuff to reduce it to cylinders?
>
> Keep thinking...
>
> Bruce
> NJ
>

I tagged my thoughts on clay/graphite crucibles to Andy's reply too.

You might check out petroleum coke, I believe it comes in barrel shaped 
pellets. I don't know how large or how available they are. I also have 
serious doubts about their survivability, of course if they catch fire just 
give em some air and forge on. <grin>

Frosty
-------------------------------
If it ain't forged
it ain't real.
Wrought iron is.
The FrostWorks

Meadow Lakes, AK.

http://www.artmetalradio.com/