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rolling mill questions



 
 
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  #11  
Old September 17th 06, 03:52 PM posted to rec.crafts.jewelry
Abrasha
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Posts: 298
Default rolling mill questions

br wrote:
I doubt that "wobbles and bends" would be a big problem as the disks
will be hand-punched.


You may not have trouble because of "wobbles and bends" but you'll have plenty
of other problems. You better have a damn good punch for that, because if you
don't you are going to have a hell of a time punching circles out of .1 mm thick
sheet. That is not even sheet anymore, but almost foil. If you punch is not
made to a very tight tolerance, you will drag the sheet into the punch and you
will not get a clean cut. I have circle cutters, that have decent tolerances,
and I cannot cut anything very clean that is thinner than .3 mm. For larger
circles I make my own punches, that cut just fine. I leave them unhardened,
because it doesn't really matter for gold, if they are hard or not, and I do not
have to cut thousands of circles.

Am I correct in assuming that the "straightness" of
the ribbon depends on the parallelism of the two rollers? Concerning a
polished surface (only one side needs to be polished); would it be feasible
to use a long strip of highly polished spring steel, run through the mill at
the same time as the gold ribbon, to polish the surface?


That is the single best way to destroy your rolling mill in short order! (Well,
maybe not neutralizing your sheet well from acid after pickling is a better way)

If I'd see you do that in my shop, I'd kick you out the door faster than you can
say "Oh ****!" I have seen idiots doing stuff like that with bunched up steel
wire to create an "interesting" rolled pattern on sheet. They ended up with the
patterns in the gold and silver, as well as on the rolls!

Rolls of mills are usually only case hardened, which hardens only a very thin
outer layer of the rolls.

--
Abrasha
http://www.abrasha.com

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  #12  
Old September 17th 06, 03:52 PM posted to rec.crafts.jewelry
Abrasha
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Posts: 298
Default rolling mill questions

Carl wrote:
When lemel_man put fingers to keys it was 9/15/06 4:17 AM...

....
Basically, when you roll a wire or strip the width increase depends on
the ratio of the previous width to thickness. The bigger the ratio the
smaller the increase, but its not linear. I worked out some sort of
correlation between the ratio and percentage increase and found I could
get pretty accurate results, especially for ratios smaller than about
10:1. Based on that work, I would say that 1.2mm square wire rolled down
to 0.1mm would end up close to 4mm wide.
For what its worth, my calculations suggest that 2.2mm square wire
rolled to 0.1mm would end up around 10mm wide. But as said above, the
accuracy at a ratio of 100:1 is not good. With more work it could
probably be improved, but in my case its just not worth it.


Hmmm...

http://c-24-63-36-176.hsd1.ma.comcas...llingChart.gif

Add some more points and it could be useful, Yes?


I could not figure out how to read that graph.


There has _got_ to be something like this out there in the literature.


I have a table in one of my German training books, that has a chart that lists
the dimensions of rectangular wire you end up with from on a number of
dimensions of square wire as starting points.

Abrasha
http://www.abrasha.com

  #13  
Old September 17th 06, 03:58 PM posted to rec.crafts.jewelry
Peter W.. Rowe,
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Posts: 355
Default rolling mill questions

On Sun, 17 Sep 2006 07:52:26 -0700, in rec.crafts.jewelry Abrasha
wrote:




Not true! Ted, there you go again! Once again you speak of things you do not
know about, a bit too soon.


Lets not get personal, shall we?

And though I'd agree with you, Abrasha, about rolling down wire, Ted's not
entirely wrong either, IF his experience and comments refer more to rolling down
stock that starts out wider. If you start with an ingot that's an inch or two
wide, and then likely around a quarter inch thick such as most ingot molds
produce, the lateral spreading will be a fairly low percentage. No doubt this
is where Ted's comments spring from.

!

I have a table in a German training book for goldsmiths, that lists the
thicknesses and widths one will end up with for a number of square starting
stock. Comes in very handy from time to time. If there is interest, I can scan
the page, and put it on my site for a few days.


I'm sure there'd be interest. I for one, would enjoy seeing it. thanks for the
offer.

Peter
  #14  
Old September 17th 06, 04:22 PM posted to rec.crafts.jewelry
Peter W.. Rowe,
external usenet poster
 
Posts: 355
Default rolling mill questions

On Sun, 17 Sep 2006 07:52:47 -0700, in rec.crafts.jewelry Abrasha
wrote:

br wrote:
I doubt that "wobbles and bends" would be a big problem as the disks
will be hand-punched.


You may not have trouble because of "wobbles and bends" but you'll have plenty
of other problems. You better have a damn good punch for that, because if you
don't you are going to have a hell of a time punching circles out of .1 mm thick
sheet. That is not even sheet anymore, but almost foil. If you punch is not
made to a very tight tolerance, you will drag the sheet into the punch and you
will not get a clean cut. I have circle cutters, that have decent tolerances,
and I cannot cut anything very clean that is thinner than .3 mm. For larger
circles I make my own punches, that cut just fine. I leave them unhardened,
because it doesn't really matter for gold, if they are hard or not, and I do not
have to cut thousands of circles.


True again, that most circle punchs are intended for thicker metal, and have a
bit more clearance between punch and die for that application.

I've used ordinary light weight paper punches with foil. they work well. There
are a wide range of odd and interesting shapes available in the "crafts" stores
for people and kids doing scrapbooks and similar home projects that use paper
punches. The things are cheap. Not sure they'll hold up to thousands of holes
in metal, but at less than ten bucks each, buy another punch when it starts to
get dull.

Or, rather than the punches that use a punch and die, use the single type of
punch used for shim stock, leather, etc. Some are called arch punches, and have
a full hollow center inside the sharpened cutting edge with a side cutout to
retrieve cut parts. Others are like the cheap cutters sold alongside dapping
punches from india. Either, used against a firm cutting surface like a copper
sheet, might work well enough with gold foil. You might want to anneal it for
this type of punch.

Am I correct in assuming that the "straightness" of
the ribbon depends on the parallelism of the two rollers? Concerning a
polished surface (only one side needs to be polished); would it be feasible
to use a long strip of highly polished spring steel, run through the mill at
the same time as the gold ribbon, to polish the surface?


That is the single best way to destroy your rolling mill in short order! (Well,
maybe not neutralizing your sheet well from acid after pickling is a better way)

If I'd see you do that in my shop, I'd kick you out the door faster than you can
say "Oh ****!" I have seen idiots doing stuff like that with bunched up steel
wire to create an "interesting" rolled pattern on sheet. They ended up with the
patterns in the gold and silver, as well as on the rolls!


I worked for some time, years ago, in a small two person (including me) shop in
Detroit, located in an office building with lots of other jewelers, many of whom
were of middle eastern origin. Big families, and sometimes they'd bring their
kids to hang around the building too. Nice kids. Well, my boss was a nice good
looking blonde lady whom these kids adored. So we'd now and then have these
kids hanging around our shop when they were bored, and Mary Jo sometimes woiuld
let them amuse themselves by rolling down pennies in the mill. One time,
apparently, shortly before I got there, and shortly after she'd just purchased a
nice new rolling mill, she'd given a kid a penny to roll down, and then was
distracted by answering the phone. The did finished the penny, and looked for
something else cool to flatten. Came up with some used jewelers saw blades and
a couple #12 scalpel blades for cutting rubber molds. As Mary Jo got off the
phone, he asked her dejectedly why these cool things hadn't also gotten long and
flat? I'm glad I wasn't there to see her reaction. Apparently, she didn't
actually kill the kid, but it was close. It was a combination mill, so we
couldn't even get the rolls reground or it would have messed up the wire
grooves. So for years, I had to just avoid that part of the rolls with the
sawblade and scalpel blade imprints, which fortunately, was right along an edge
of the roll.

On the other hand, I often do pretty much this same thing to produce an embossed
pattern on the metal. I like to use engine turned (guilloche) patterns on some
of my work, and have the machine to do so. But for some less costly work, the
time required to actually cut a real guilloche pattern on the metal isn't
warranted. So I cut that pattern on a three inch wide sheet of starret flat
ground stock that I'd polished on one side (the side I cut), and had had
reground on the other to a surface finish slightly better than the surface of an
OLD somewhat beat up flat mill I've got, with three inch wide rolls. I roll
print my metal with that sandwich. The reason this works is that the steel
sheet has a better surface than the mill, so it doesn't make it worse, and it's
the full width of the mill, distributing pressure, and is curved as well, though
to a wider arc than the mill rolls, but again distributing pressure. And it's
not hardened. This works fine. The metal takes a fine impression from the
sheet, and the mill is not damaged. In use, it's very important that the
embossing steel sheet is longer and wider than the piece being embossed, so that
as the gold or silver finishes up, and exits the mill, the embossing tool is
still there in full contact with the mill. Now, though, with the gold gone, the
pressure on the mill is off, so the ending (or at the beginning starting) edge
of the embossing tool does not cause a mark on the mill.

In short, you CAN do this, IF you think it through carefully and understand that
doing it wrong will destroy your rolls.

But for simply polishing the metal during rolling, having the rolls themselves
polished would be easier perhaps. Just be sure the place doing it understands
that the rolls MUST remain highly concentric and cylindrical. This is not as
easy as it sounds. It's high precision machining, and likely to cost some
money, if you want the resulting rolls to be able to process metal as thin as
the foil you wish.

Peter
  #15  
Old September 17th 06, 07:44 PM posted to rec.crafts.jewelry
Carl 1 Lucky Texan
external usenet poster
 
Posts: 57
Default rolling mill questions

Peter W.. Rowe, wrote:
On Sun, 17 Sep 2006 07:52:26 -0700, in rec.crafts.jewelry Abrasha
wrote:




Not true! Ted, there you go again! Once again you speak of things you do not
know about, a bit too soon.



Lets not get personal, shall we?

And though I'd agree with you, Abrasha, about rolling down wire, Ted's not
entirely wrong either, IF his experience and comments refer more to rolling down
stock that starts out wider. If you start with an ingot that's an inch or two
wide, and then likely around a quarter inch thick such as most ingot molds
produce, the lateral spreading will be a fairly low percentage. No doubt this
is where Ted's comments spring from.

!

I have a table in a German training book for goldsmiths, that lists the
thicknesses and widths one will end up with for a number of square starting
stock. Comes in very handy from time to time. If there is interest, I can scan
the page, and put it on my site for a few days.



I'm sure there'd be interest. I for one, would enjoy seeing it. thanks for the
offer.

Peter


I have no real experience with these issues, but in one of the previous
posts, someone mentioned the mill's roll diameter being a factor. maybe
Abrasha and other's experiences seem disparate due to large differences
in mill roll diameters?

Also, anyone know of a way the circles the OP needs could be
electrofomed? That might be an approach to the problem with some merit.

Carl


--
to reply, change ( .not) to ( .net)

  #16  
Old September 17th 06, 08:00 PM posted to rec.crafts.jewelry
Peter W.. Rowe,
external usenet poster
 
Posts: 355
Default rolling mill questions

On Sun, 17 Sep 2006 11:44:31 -0700, in rec.crafts.jewelry Carl 1 Lucky Texan
wrote:


I have no real experience with these issues, but in one of the previous
posts, someone mentioned the mill's roll diameter being a factor. maybe
Abrasha and other's experiences seem disparate due to large differences
in mill roll diameters?


The roll diameter has a minor effect on the degree of spreading. That would
make it difficult to do a very precise formula or chart, but not to the
difference in degree of spreading discussed in the thread. I think the
differences are due to most of us talking about rolling wire down to thin stock,
which is a very great reduction in thickness compared to the WIDTH of the stock,
while Ted's experience or discussion of rolling seems more related to what
happens when rolling wider stock such as a normal ingot, rather than wire.


Also, anyone know of a way the circles the OP needs could be
electrofomed? That might be an approach to the problem with some merit.


An interesting thought, though getting very uniform thickness might be a
problem, especially since edges might tend to be thicker. And the tooling for
the process might be tricky to think up. Also, electroforming karat gold
alloys to a consistant alloy composition is not easy to do. Usually, it
requires proprietary technology using rather sophisticated electrolytes, as well
as complex plating methods. Possibly things like multiple anodes of different
compositions, computer controlled with seperate power supplies, in order that
the deposition rate of the different metal constituents remains within the
alloy composition standards required. Remember that most gold plating solutions
produce a desired color range, but at essentially high karat gold, often around
23K or higher, even when the color looks like 14K or 18K etc. Getting an actual
lower karat deposit isn't so easy because the baser metals plate out at
different rates at any given voltage, so the bath composition changes over time,
changing the deposit composition along with it.

But it also brings to mind another option worth considering. while
electroforming to actually make the whole disk might be diffucult,
electroETCHING to punch the disks from sheet stock is certainly a very viable
idea. The process is very well suited to cutting precise shapes from thin
metal stock, and might be easier than punching given the thin stock. For gold,
it would work best, with a cyanide based etchant rather than acid, so safety
concerns would need to be met, but the process itself is not that complex. And
since electroetching would require very little clearance between adjacent disks
cut from flat stock, the waste would be less, though some of it would need to be
recovered from the etchant solution rather than remaining as easily melted scrap
metal. But that's not that hard to do either. Just electroplate it or "cement"
it back out again.

Peter
  #17  
Old September 18th 06, 06:26 AM posted to rec.crafts.jewelry
Carl
external usenet poster
 
Posts: 38
Default rolling mill questions

When Abrasha put fingers to keys it was 9/17/06 10:52 AM...

Carl wrote:
When lemel_man put fingers to keys it was 9/15/06 4:17 AM...

....
Basically, when you roll a wire or strip the width increase depends on
the ratio of the previous width to thickness. The bigger the ratio the
smaller the increase, but its not linear. I worked out some sort of
correlation between the ratio and percentage increase and found I could
get pretty accurate results, especially for ratios smaller than about
10:1. Based on that work, I would say that 1.2mm square wire rolled down
to 0.1mm would end up close to 4mm wide.
For what its worth, my calculations suggest that 2.2mm square wire
rolled to 0.1mm would end up around 10mm wide. But as said above, the
accuracy at a ratio of 100:1 is not good. With more work it could
probably be improved, but in my case its just not worth it.

Hmmm...

http://c-24-63-36-176.hsd1.ma.comcas...llingChart.gif

Add some more points and it could be useful, Yes?


I could not figure out how to read that graph.


It shows the four data points that lemel_man gave. The blue lines
connect the corresponding pairs (square and flattened to 0.1mm). The
grey line just marks the 1:1 ratio of height to width.

I bet that if measurements are taken throughout the rolling process that
those lines turn into curves. Having those curves would be helpful when
you aren't starting from square stock. Seems to me.

It also seems that it's important to note the diameter of the rollers.
Yes? No? The degree of curvature certainly makes a difference on a
hammer face. thinking... well, OK, the practical difference between
2,3,and 4 inch rollers is probably very small.


There has _got_ to be something like this out there in the literature.


I have a table in one of my German training books, that has a chart that lists
the dimensions of rectangular wire you end up with from on a number of
dimensions of square wire as starting points.


Hmmm... do they mention roller diameters?

- CW

  #18  
Old September 18th 06, 06:41 AM posted to rec.crafts.jewelry
Abrasha
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Posts: 298
Default rolling mill questions

Peter W.. Rowe, wrote:
On Sun, 17 Sep 2006 07:52:26 -0700, in rec.crafts.jewelry Abrasha
wrote:



Not true! Ted, there you go again! Once again you speak of things you do not
know about, a bit too soon.


Lets not get personal, shall we?


And why not, if he has made a factual sounding statement that is not correct?
[[this paragraph edited by moderator]]


And though I'd agree with you, Abrasha, about rolling down wire, Ted's not
entirely wrong either,



Oh yes he is.

IF his experience and comments refer more to rolling down
stock that starts out wider. If you start with an ingot that's an inch or two
wide, and then likely around a quarter inch thick


Oh give me a break Peter. That is not wire! That is heavy plate! Any wire, I
repeat ANY wire, whether is is 1.2 square or round or 10, or 20 mm, will spread
laterally a great deal more than 2-4%. And the bigger the reduction in
thickness each step when rolling, the bigger the lateral growth.

such as most ingot molds
produce,


Like I said, that is not wire, but an ingot, which is plate (or sheet, if it is
thinner). I rest my case.

the lateral spreading will be a fairly low percentage. No doubt this
is where Ted's comments spring from.


No it is not. The original poster was clearly talking about 1.2 mm wire. And
Ted's response was: "IE your 1.2mm wire will go down to the thinness you want
BUT wont get any wider!!."

--
Abrasha
http://www.abrasha.com

  #19  
Old September 18th 06, 08:53 AM posted to rec.crafts.jewelry
lemel_man
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Posts: 22
Default rolling mill questions

Abrasha wrote:

...
I have a table in one of my German training books, that has a chart that lists
the dimensions of rectangular wire you end up with from on a number of
dimensions of square wire as starting points.


If you want a strip of width W, thickness T, a pretty good approximation
of the side S of square wire that you start with is...

S = Cube root of (W squared times T) or S = (W**2 * T)**(1/3)

For example, you want a strip 2 by 0.25mm, you roll a square wire of
side Cube root of (4 x .25) = Cube root of 1 = 1

I have only one rolling mill so I haven't tried with rolls of different
diameter. Mine are 65mm.


--
Regards, Gary Wooding
(To reply by email, change feet to foot in my address)

  #20  
Old September 19th 06, 07:17 AM posted to rec.crafts.jewelry
ted frater
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Posts: 133
Default rolling mill questions

[[moderator's note: This posting was delayed due to moderator error. Was sent
Saturday the 16th]]

lemel_man wrote:
ted frater wrote:

...snip...
This one is something I can help you with.
Putting it simply, a rolling mill makes metal thinner IN the direction
of the rolling.
IE your 1.2mm wire will go down to the thinness you want BUT wont get
any wider!!.( ok I know there will be someone who will say it actually
does get wider by about 2/4 %)



I am surprised that this myth continues to be preached. Its simply not
true. I found that out when I wanted a 100mm 0.25mm x 1mm strip. I took
a 25mm length of 1mm square wire and rolled it down to 0.25mm. That
should do it, right? Wrong. I got a 50mm strip 2mm wide. That's when I
did the experiments. I did lots, plotted the results on a graph, applied
some curve fitting algorithms and came up with a pretty nasty equation.
I simplified it a bit and wrote a program that I've been using for a
number of years. Its not 100% accurate, but close enough to be extremely
useful. It also varies a little with the metal being rolled. I feed in
the width and thickness of the strip I need and it tells me the size of
the square or round wire I need.
For example, suppose I want a 3 by 0.2 strip 400mm long. It tells me I
need to start with 161.25mm of 1.22mm square wire, or 162.81mm of 1.37
diam round wire, and it will weigh 2.688gm in 9ct yellow gold.

You don't believe me? try it yourself. You must start with well annealed
wire and roll it aggressively, ie. minimise the number of passes and
anneal frequently. In the example I would set the roll to give 0.2mm
thickness in one pass, measure the result, adjust for the error (its
never too thin), and do the correction pass.
I can't believe I've got the only magic rolling mill in the world.


If you roll say 2in wide by 1/8in thick it doesnt get wider. it gets
longer. I would cast silver 4in long by 2in wide by 1/4in thick and
tuern that into 1/16in thick strip. Never got wider.
yuor probably right with the sizes your talking about. I never had
the need to work round/square wire to flat strip. I always used wide
stock to start with.
Be that as it may,
I woke up in the middle of the night last night and eureka!!. theres a
co that makes just the sheet our friend is looking for.
Many years ago back in 1970 i was doing lots of enamelling and used
paillions as inlay in the enamel in gold and silver. Stll have plenty
left. Aught to use them up.
Bought these from Bayeler&Co.sa. in Geneva. Now Ive just had a look on
the net and there no reference anywhere for them perhaps someone else
might be more lucky.
they made gold sheet in the thickness you need and would make up the
discs you want as well IF there still in business.
My last contact was in 1978 some 28 yrs ago. dug out their file and
catalogue. nice to look back. anyway ill find out on Monday if there
still in business.
What do you want the discs for?
just curious.
Ted


 




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