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Scrap to ingots for sheet


#1
Is there anything in particular or special that I need to know or
do to the scrap before, during, or after 

there are all sorts of things that you can do. I’m not even going to
scratch the surface. I make wire every day, and though I do make
sheet, it tends not to be of the same quality as that from the
bullion dealers. Wire I can make to a very high standard, so I’ll
focus my advice on that.

Make sure your metal is very clean before you melt it. If you are
working to a hallmarking standard, add a small amount of higher carat
material (eg. fine silver, 22ct gold) to ensure that the fineness of
the metal is high enough. You should have removed any solder before
melting up, because it lowers the carat of your metal, and ruins the
working properties of the metal.

Melt your metal in a crucible with a low-oxygen flame. I often add a
well-mixed paste of charcoal, borax and water before I add the metal

  • this serves to remove some of the base metals, and if you intend
    to roast the metal for a long time like this, ignore the advice
    above about adding finer metal.

Then, using casting sand or similar, make a one-use ingot mould. I’m
usually working with a lot less than an ounce of metal. I use a
rectangular piece of steel to push a depression into the sand, then
pour straight into that. That gives it really neat sides, and I much
prefer the open method to using steel ingot blocks or an open iron
mould. The resulting ingot will look a bit like a loaf of bread, but
tiny.

Pickle and clean the ingot, then hammer the top side and end surfaces
to compact them. Anneal and pickle. Then either hammer the ingot into
shape, or use a rolling mill with holes for square wire. If you only
have a flat roller, it might be too time consuming to make your own
wire - does anyone else have a good method?

Any “feathering” on the edges of the metal should be filed off, and
if you see this feathering every time you roll the metal, it may be
too far gone, and need to be melted up again - the feathering can
get worked into the structure of the wire, causing it to flake or
break when you try to bend it.If you have round or half-round
rollers on your mill, set them so they will just touch the metal,
and roll your square wire through 4 times, one for each surface (you
only need do it twice if they are fully round rollers). This removes
the flange left by the square rollers, and softens the edges very
slightly - I actually think this is better than true square wire,
because it’s a lot less likely that you’ll unevenly round off the
edges while working with it. If you are making round wire, continue
this process to soften the edges further - this makes it much easier
to draw it through round holes.You must have a draw plate.

Unless you want to do it like the ancients did (if you do, email me,
and I’ll send you the link for a journal article. Draw plates are
fairly similar. Don’t try to draw more than 3mm wire by hand, as it’s
more effort than the metal is worth, and less than 0.5mm can get very
annoying. Once you have your wire, it will be curved. Straighten it
with one of two methods. For round wire only, you can twist it - 8
turns left, 16 turns right then 8 turns left again to bring it back
to it’s original shape. Do this while keeping the wire tense, and it
will be very straight. The alternative, for anytype of wire, is to
clamp it in a vice at one end, and hold it in tongs at the other end.
Then, carefully move your torch flame up and down the wire, while
keeping it tense. It will gradually straighten AND it will be
annealed. Always pickle and polish and clean the wire before use, and
it will look as good as anything from the bullion dealer.

Hope there aren’t too many typos; got to get to work now! Comment and
abuse to the usual address

Jamie
http://primitive.ganoksin.com


#2

Everyone who makes their own sheet and wire stock has different
methods for doing it. I’ve been teaching my students to make their
own stock for over 30 years. Yes, having clean scrap will be
important, solder being a contaminant and potential problem. You’ll
also want to be sure the alloy in your metal is a “rolling” alloy,
rather than a “casting” alloy. Alloys designed for casting will flow
well, but not necessarily roll out well.

I have used a reversible steel ingot mold for years, in a large
size, and smaller size. They offer the easiest, fastest, and most
accurate method of getting the best initial ingot shape before
rolling. I either very lightly oil mine, or soot them to prevent
metal from sticking to them. I also heat them with a torch before
pouring an ingot, as moisture tends to be drawn to the cold steel,
and steam is not want you want when pouring hot metal into an ingot
mold! If I keep my torch flame off the clamp, it is cool enough to
remove safely by hand after pouring the ingot.

I’ve never needed to hammer an ingot before rolling. Let’s call the
rolling mill a “rotary hammer”, shall we? What used to be done by
apprentices with hammers, is now rolled out with a rolling mill.
Same operation, much faster and more accurate with a rolling mill.
I’d advise, when rolling round ingots through the rolling mill to
create square stock, using the grooved part of the rolling mill, to
always allow some space between rollers. Using the grooves, a square
ingot gets condensed and pushed outward as pressure is applied. The
square ingot will need space to expand outward as it is rolled. If
enough space between the rollers is allowed, then this happens
naturally, and upon turning the ingot a quarter turn and re-rolling
it, those pushed-out corners will then be pushed back into a perfect
square again. The flanges or fins formed on the corners will usually
be caused by the mill being too tight, and the expanding ingot
extruding through this tight fit. Hope this helps…

Jay Whaley


#3

Further to Jamie’s great explanation, if you want to roll your
ingots into sheet then a closed mould is better. There is a steel
mould comprising overlapping halves clamped together which produces
ingots of a fixed thickness and a variable width. When the molten
metal is poured into the end of the cavity, any dross and porous
metal will accumulate at the top ie, at one end of the ingot. This
end is cut off leaving a very clean ingot. If any surface defects
appear while rolling and annealing they can be burred out. Provided
the cutting goes no deeper than the final sheet thickness, further
rolling will lower the whole surface until the cut-out parts
disappear.

Regards, Alastair


#4

Hey Jay,

Everyone who makes their own sheet and wire stock has different
methods for doing it. I've been teaching my students to make their
own stock for over 30 years. Yes, having clean scrap will be
important, solder being a contaminant and potential problem.
You'll also want to be sure the alloy in your metal is a "rolling"
alloy, rather than a "casting" alloy. Alloys designed for casting
will flow well, but not necessarily roll out well. 

I was thinking about this the other day.

Don’t all alloy/metals that we use have to be cast at some point?

I made a mistake the other day, I annealed my metal before rolling
it enough, cracked the corners… oh well I’ll melt it down again,
this time I’ll make my ingot a smaller dimension to start with.

Regards Charles


#5

Jay,

I sure appreciate the help folks have offered. I never realized
that solder on scrap parts was a problem. Everyone stressed "clean"
scrap more than I expected. 

Is there any way to improve casting scrap for rolling? Maybe adding
some fine silver.

Thanks for all the help and I’ve just ordered an ingot mold.

Regis


#6

Hi Jamie

fab little description and just as I was about to ask about this
very topic. one query I hope you can help with…

i tend to find I often get ‘brittle’ bits or holes in the bar once
its hardened. any idea what I’m doing wrong?

(P.S. have you checked out the island of Gotland, Sweden, for viking
jewellery)

cheers Annika


#7
If any surface defects appear while rolling and annealing they can
be burred out. Provided the cutting goes no deeper than the final
sheet thickness, further rolling will lower the whole surface until
the cut-out parts disappear. 

Thanks for this Alastair. I cast (past tense of the verb
to cast?) a few ingots a while ago, but got a bit disillusioned due
to some surface defects. They’ve lain in my drawer ever since. I’ve
give this suggestion a try before continuing to roll them out.

Helen
UK