[TheForge] Chip forge

Sat Mar 4 19:19:36 EST 2006

Jerry,
An excellent summation, but maybe it can be fined tuned a bit.

My rant: It is quite true that broken ceramic chips are what commercial 
'forges' use. They can be ordered from Flamefast in England for this very 
purpose. However, after a lifetime of watching perfectly good tooling 
replaced in the market by c**p, with no other virtue than the fact that by 
cheapening the product, it allowed more sales meetings in Hawaii, I for one 
do not consider "regular industrial grade" manufacturing practices as a 
badge of honor, but rather as something to be viewed with suspicion if not 
outright contempt. I need hardly point to our own famous examples: Big tail 
fins and chrome, while the rest of the world retooled and made better cars; 
or how about hydraulic shears because they could be sold for more money, in 
spite of the fact that they break down constantly, and were never 
appropriate technology unless the shear was combined with a press? Or, the 
much smaller example of a one-dollar "U" shaped rubber welding lens seal 
being taken off the market so that the company's $2.50 folding hard plastic 
seal (with light leaks all over the place) could be sold more easily. I 
think any man who worked the trades since world war two can match these with 
a hundred other stories.

I think the shovel would probably work just fine, but actual chips leaves us 
with "a problem down below."
When the flame is introduced in the fire box it needs both a generous space 
and enough total exit area in the grate (or whatever else is used to prevent 
the ceramic media from choking the fire box) to allow buoyancy to overcome 
back pressure. The English ceramic chip brazing hearths can afford to use 
shaped grates to supply just enough room for a fan blown burner to force the 
flame through a narrow slit, thus avoiding the invasion of small ceramic 
chips, because their main purpose is brazing. All other uses for their 
hearths are strictly secondary. If brazing is your main goal, they make fine 
sense, but for forging they're going to be weak in the knees. My own main 
goal for these hearths is also brazing, but this is a forge working group.

A very restricted grate in a small fan blown brazing hearth makes sense; the 
smaller a part is, the stronger and cheaper it is to replace; the smaller a 
part is, the less load there is on it. Heated ceramics have a little problem 
with carrying heavy loads. So small grates in small brazing hearths, aren't 
likely to work very well when they are increased to the size needed for 
serious forges, which brings us to kiln shelf strips. BTW, anybody who 
thinks they are going to overcome the back pressure from little bitty chips 
with just any old blower, had better take another look at those monster 
motors featured on English fan blown hearths; you can all just forget about 
using hair dryers, or baby size squirrel cage fans.

High alumina kiln shelving can be economically purchased and cut into strips 
with cheap masonry friction blades, leaving lots of space for flames to be 
drawn through the right kind of ceramic media and maintaining good strength 
by turning the strips edge up. The media above the strips must be of fairly 
large size, and uniformity, so as not to fall through the grating, or to 
pack down; enter ceramic balls. The upper portion of ceramic ball media only 
needs to be large enough not to fall through the spaces between the lower 
balls. The guys over in Europe could use LECA for the upper layers because 
they can get larger diameters over there, which we can't get here. However, 
with a deliberate intermediate layer between the lowest balls and the upper 
balls, it should be quite easy to get down to 3/8" balls, which anyone 
should be able to push parts into and out of without damage--especially with 
the use of a trowel to help the process.
Mike P.

----- Original Message ----- 
From: "Jerry Frost" <frosty at customcpu.com>
To: "Sponsored by ABANA" <theforge at mailman.qth.net>
Sent: Friday, March 03, 2006 6:04 PM
Subject: Re: [TheForge] Chip forge

> There's been some discussion about "chip" size and material. The pictures 
> I've seen of commercial chip forges have just that, chips. They look like 
> gravel.
>
> Packing is just what you don't want; you want a fairly unrestricted flame 
> flow through the chips. Comments from people who have used chip forges say 
> it can be hard to push small or delicate work into the chips. I think this 
> is what lead to the discussion of making or buying spheres. I figured I'd 
> use a shovel to cover delicate work but there might be damage pulling it 
> out. I don't know.
>
> I've given a couple shapes some thought:
>
> Spheres will make for the least restriction in flame flow but provides the 
> least surface area/volume ratio of any shape so heat transfer in and out 
> will be minimum. Making spheres will I think be the most hassle as well.
>
> Gravel like chips will be pretty easy to produce and having a high surface 
> area/volume ratio will provide good heat transfer. Like I say making chips 
> should be pretty straight foreward. Choose the refractory of your choice, 
> ram, roll or cast it to the desired thickness, say 1/2". Let it dry, set, 
> etc. and break it up till it passes a 1/2" seive. Lastly fire them like 
> ceramic, using your chip forge of course. <grin>
>
> Two minor (maybe) drawbacks being:
>
>        1) Uniform gradation. The chips need to be pretty close to the same 
> size to avoid packing so you'll end up with waste making them by the above 
> method. Depending on the refractory you may or may not be able to 
> reconstitute it with water and repeat the process.
>
>        2) Keying. Keying means they'll lock together because of their 
> irregular broken shapes and may cause damage pushing work in and pulling 
> it out. Smoothing them a little after you break up the refractory will 
> help but not eliminate the (maybe) problem. You also wouldn't want to 
> smooth them too much or you lose surface/volume ratio.
>
> As usual there's a compromise, or at least I think so. Here's the idea I'm 
> going to try baring somebody else coming up with a good workable method, 
> source, etc. I'll use a high temp rammable refractory and hammer it to a 
> sheet 1/2" thick and then cut it into 1/2" cubes. While it's still plastic 
> I'll gently roll the corners so they're not sharp. Hopefully this'll make 
> "chips" with a good compromise between free flame flow and good 
> surface/volume.
>
> Here's an idea for making spheres. If you use the above method to make 
> 3/8" cubes and roll them between boards 1/2" apart you will end up with 
> spheres close to 1/2" dia. How well a refractory will stand up to being 
> rolled from cubes to spheres will depend on how plastic the refractory is. 
> If it works you'll be able to roll a lot of spheres at the same time.
>
> Another variation on the above process is to roll "ropes" of the desired 
> dia. and cut them to length. (I' ve been saying 1/2" but I just picked it 
> arbitrarilly and another size may be better. I don't know)
>
> Frosty
> -------------------------------
> If it ain't forged
> it ain't real.
> Wrought iron is.
> The FrostWorks
>
> Meadow Lakes, AK.
>
> http://www.artmetalradio.com/
>
> From: "Dan Brewer" <danqualman at gmail.com>
>
>
>>
>>
>> __I seen discussion about the forge but no one has mentioned the size of 
>> the
>> balls.  Do they need to be balls or irregular pieces that pack similar to
>> coal/coke.
>> Dan in Auburn
>
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