Really! I too have seen larger mills on ebay which are used
industrial forming etc., not what I had in mind. I was thinking of
following the basic design for jewellery mills but increase the
size maybe 3 or 4 times. I believe I can do it for around $500 for
materials, perhaps more for good quality round stock of induction
steel up to 4" in diameter.
There are reasons they are so big, the separating force that a 12"
roll must withstand is huge and must have a design that can handle
it. To have a 12" wide roller that will nor flex too much you will
need to have at least an 8" diameter roll. You will not even be able
to buy the roll stock for $500. The frame to keep the rolls in place
will be huge as well. Much less the gears, drive components etc. The
12" rolls I have seen are in the 15-20 HP range and weigh thousands
of pounds. This not just to sell large equipment but is what is
required to do the job.
As I said in an earlier post, my concept is to just use the basic
design of present jewellery mills and increase the size 3 or 4
times. The rolls would be 3 to 4 inches in diameter and up to 12
inches long (plus extra for the bushings etc.). The frame would be
1/2 inch plate and the bushings would be case iron or brass. Yep it
would be a heavy thing, maybe 200 to 300 pounds.
I think your numbers are way off.
When scaling up a machine like a mill by 3-4 times everything goes
up exponentially by 3-4, it is not a linear scaling factor. My little
mill (100mm with 60mm dia rolls) is not quite portable at 100 pounds,
no way you can make a 12" wide one at 300 pounds. 4" steel round
weighs 43 pounds a foot.
Look at pictures of small mills in catalogs, a frame made out of
1/2" steel might as well be made out of cooked pasta. There are very
good reasons why mills are built this way and weigh so much, the
forces and stress of even a gentle roll are really really nasty.
And don’t forget the gear reduction drive, direct drive mills are
not fun to even attempt to use, even on a 2" mini
Make and sell enough stuff to buy one and you will come out ahead.
They last forever and are good for a tax right off.
[eBay link removed. sorry, no eBay links on Orchid]
That is link to a model on ebay that I was talking about. Its used
for reducing steel plate up to 9 inches wide. If they use hot rolled
or cold rolled methods I’m not sure.
If I can get a 6 inch mill from my idea, I’m happy it will sure
increase production. Granted my idea my be full of hot air, but
nothing ventured nothing gained. I’m reasonably sure that a 6 inch
model will work, after 8 not so much, but it’ll fun to try.
It might be the height of hubris on my part, but I think its possible
to build a larger mill suitable for my purposes (as I explained in
the post you’re quoting from).
I was just checking (to get my facts straight) the specs of the
industrial rolling mills that we are comparing my idea/design too.
First they are designed to reduce the thickness of plate steel in a
process called cold rolling (steel formed at below forging
temperature). The pressure, stresses and forces needed are a lot
more then what is needed with annealed copper, silver etc. Secondly
the rate that they do this work is measured in meters per minute.
I’ve seen a range of 30 mpm to 1000 mpm. This is far different to
what I am thinking of where the rate is at best a foot a minute,
again in my mind a vast reduction of pressure, stress and forces.
Thirdly what I want the mill to do is to reduce the thickness of
Mokune-Gane billets which can’t take a great deal of stress.
Keeping the above in mind I still maintain that my idea could work.
If you disagree that’s fine and really the proof is in the pudding.
This thread and the responses to my off handed comment has put a bit
of a spur in my behind. Unfortunately with starting a new business,
teaching and getting some new stock for the Xmas run up has eaten up
my time for the next few months. I’ll post pictures of the completed
mill when I have a chance to get around to it.
It is acceptable for most of our applications if our thickness of
sheet when we roll it is close, if for example you want 18 ga, 17
to 19 ga will often be ok.
This is a bad example. Personally, I cannot imagine a situation where
or - a gage would be o.k. But if it is, do not bother with rolling
mill and simply buy metal from a refiner.
In my shop, we measure thickness of a sheet with micrometer and
tolerance of 0.02 mm is the maximum I will accept. And only on the
plus side.
Thirdly what I want the mill to do is to reduce the thickness of
Mokune-Gane billets which can't take a great deal of stress.
Personally I would like to hear from James Binnion on this, but
trying to reduce the forces, by reducing the pinch and or the speed,
will actually increase the forces inside the billet and cause
shearing along the weakest grain boundary which would probably be
between to metal types. Almost all problems with rolling, spinning,
coining, and forging are caused by INSUFFICIENT FORCES. Some times
Tim Allen as the “Tool Guy” is right.
Keeping the above in mind I still maintain that my idea could
work. If you disagree that's fine and really the proof is in the
pudding. This thread and the responses to my off handed comment has
put a bit of a spur in my behind.
Well, Chris, I’ve said a couple of things on this thread. I’m an
expert with a rolling mill but I’m far from it when it comes to
building one. Much of it is standard engineering, though. I’ve seen
people build all sorts of things… The late Dave Gingery designed,
built and sold plans for lathes, milling machines and much more (see
Lindsay Books, assuming they’re still there). My attitude is that
anything that was built once can be built again, and somebody always
does it the first time, too… American ingenuity and all that. So,
I’m with you, at least on principle. I’ve seen a great many things
that you’d never think a normal person would have made, but they did.
“Nobody told me it was impossible, so I just went and did it…”
That is if you have a 12" lathe, a BIG milling machine, a surface
grinder and a centerless grinder, and the tooling and gear cutters
and all that, or are willing to pay for the services… I’d probably
have the frame cast, BTW… It’s a pretty huge project, and I
think many think it’s just too ambitious for the average idiot to
undertake. But I’ve been that kind of idiot myself, at times… I
would suggest that much of the talk here is about the engineering,
and much of that is to try to keep you/anyone from investing time
and energy into a large project that doesn’t work in the end…
Good Luck, as least from me!!!
First they are designed to reduce the thickness of plate steel in
a process called cold rolling (steel formed at below forging
temperature).
Cold rolling only means the metal enters the rolls cold; the forces
are great enough and concentrated enough (very high at the point of
contact) to rapidly heat the metal for plastic deformation and then
cool very rapidly through convection (surrounding plate or strip
mass, as well as cooling on the rolls) to exit a little hot (usually
straw or little less.). Hot rolling uses preheated strip or plate in
order to reduce the required forces and make a cheaper product.
Because the heat is so high the grain structure is usually very
relaxed meaning the plate has less strength and also has heavy scale.
General rule is more cooling on the rolls produces better product
with more scale, and less cool reduces product desirability but
reduces scale.
In my shop, we measure thickness of a sheet with micrometer and
tolerance of 0.02 mm is the maximum I will accept. And only on the
plus side.
That because your so cool Leonid (lol). I too deal with high
tolerances and it is always proportionate (sometimes .0005’‘,
sometimes .005’’ and occasionally .050’').
Thank you! If I may say, like you I very well aware on how idiotic I
can be, but at the end of the day if it doesn’t work well my skills
will have improved and maybe next time my design will be better.
In fact I do have access to fairly large machines (lathes with an 8
inch throw, an old but decent milling machine, gear indexing head,
and a variety of welders). And by living in an industrially town I
can a lot of “found” metal that I can get for free or the cost of
scrap. I believe that my major cost will be the gears (I think the
cost would be worth it to get good quality).
I’m sorry that I threw out the “12 inch” comment, to many people
jumped on that figure. My plan is to work up to that size, build
smaller ones first. If I can get a 6 to 8 inch model working I would
be more then happy. In actual fact jewellery rolling mills a fairy
simple machines and if you have the equipment and time wasn’t a
factor pretty easy to reproduce.
I could go on and on about my present mill and my repairs, about some
design problems that I can foresee, at this point I think it won’t
serve very much purpose. Unfortunately because of my comments we have
gone far away from the original intent of this thread, so please lets
get back there.
I say that if you have the time and resources then you should go for
it. Sometimes we do things simply out of desire to make something
ourselves and cost/time factors play little role in this. Good luck.
I’m rootin’ for ya!
I’m going to have to disagree with the assertion that one cannot
make straight wire or sheet stock with a rolling mill. Yes, I would
agree that a new mill, or rollers that are in "like new’ shape would
be optimal, but generating absolutely “arrow straight” stock is
extremely do-able, even routine, on a rolling mill.
The secret is to put very little pressure on the rollers during each
pass, and locate the stock very near the edge of the flat rollers.
Carefully guiding the stock along the edge of the rollers will assure
the straightest possible stock.
The edge of the flat roller, near where the stock is to be run,
serves as a visual guide, to keep the stock running true. I would
leave a few millimeters of space between the wire stock and the edge
of the rollers, so that your stock doesn’t accidentally “fall off”
the edge of the rollers. This mishap will put a bad kink in the
stock.
If it were not possible to generate perfectly straight stock with a
rolling mill, then I doubt the rolling mill would be considered a
feasible way to make stock. I make virtually ALL my stock with a
rolling mill, ordering very little from suppliers.
If anyone cares to watch the Youtube video “Fast Silver Bezel”, I am
shown making a piece of 18 ga. fine silver bezel from a poured ingot
in 2 min. 35 seconds. At the video’s end, you will see the finished
bezel stock in my hands, perfectly straight. Try placing an order for
18 ga. Bezel in less than 2 1/2 min…
The secret is to put very little pressure on the rollers during
each pass, and locate the stock very near the edge of the flat
rollers. Carefully guiding the stock along the edge of the rollers
will assure the straightest possible stock.
While this would work fine on thin sheet stock, when starting with
an ingot, this strategy will probably fail. I will assume that most
people start an ingot at least quarter inch thick (the thicker the
better), and taking too small a pinch especially in the first passes
will lead to eventual failure. The pinches on at least the first
three passes have to be deep enough for the crystal structure to be
fractured to nearly the core of the ingot. The amount of the first
pinch would depend on whether the ingot is milled or mold finished.
To prevent cracking caused by shear forces at weakened or stratified
grain boundaries caused by shallow rolling passes, plastic forming
is needed in the first several passes. While proper annealing will
soften the metal, only over annealing can equalize this un-even grain
structure. Re-growing the crystals structure by repeatedly by over
annealing can start to draw oxygen and hydrogen into the ingot
leading to cracking cause by impurities later in the rolling process.
I was always taught to do the first couple of passes from cast ingot
by way of forging them down with a hammer. You think that’ll get
deep enough to tear up the deep grain structure? I’ve noted that
forging seems to be slightly more gentle on the billet than big bites
with a roll. Or at least I can get billets of mokume to forge down
that I know would split if I tried similar reductions with a roll.
Forging doesn’t seem to generate the lateral shear stresses that
rolls do, methinks. What think you?
I’ve read (and I don’t remember the source) that an ingot should be
hammer forged to start changing the crystal structure before rolling
it in a mill. Would this have any affect on cracking?
Your discussion on grain structure is very interesting and
informative. However, I have been hand pouring and rolling out
precious metal stock for over 30 years, and just don’t have the sort
of problems you describe. Rolling out ingots of any thickness just
doesn’t seem to be at all problematic for me or my students. We roll
out ingots of platinum, palladium, 18 and 14K gold or various
colors, and make whatever forms we need in my studio.
I am puzzled by the problems you suggest with crystal structure,
grain boundaries, as well as oxygen absorption causing failures in
rolled out ingots.
I am able to easily roll out fine finished stock with a beautiful
surface finish and strength, using relatively simple studio
techniques. What am I doing right??
Sorry for jumping in and far from a materials expert… But maybe you
are just “Doing it”, sometimes people try to over think stuff and get
so bogged down in the details that they overlook simple experience
and repetition and watching the effect of what happens when you do
something different. In the case of rolling, I am guessing you take
a “Bite” that is equivalent to what you can comfortably turn the
rollers… Well just maybe the manufacturer of the rolling mill has
done the research and the heaviest possible “bite” is a little more
than the “Correct bite”.
Very often we tend to overlook the amount of functional and
ergometric engineering that goes into even the simplest tool, weather
a conscious process, or just by evolution.
[Grin] visit a tool museum, sometimes and look at the evolution of
Pliers from a simple tong…
I was always taught to do the first couple of passes from cast
ingot by way of forging them down with a hammer.
I learned a completely different way, but, given recent discussion
on Mokume? I was thinking about this a great deal the past several
weeks (so much so I passed up a purchase of a new break down mill.)
and BELIEVE this is a good idea, though definitely not a very
commercial idea. My own questions are the size, shape, and
direction/patterns of any hammer or punch I would use.
I have no experience with Mokume at all but it seems these guys use
forging to solve some shear problems and I think you couldn’t
possibly hurt your ingot unless it was too shallow before annealing.
Actually I think it could be a big improvement. Next year or the
next I may be able to do a proper test; for me the problems forging
raises, is the size of the ingot. We often use larger ingots around
30-50 ozs. and some special shapes, not just the usual rectangle. We
don’t roll all our product, but use rolling it for specialty work
and inventory control, finished size is usually 3-5 inches wide and
various lengths under 20’’ and always over .125’'.
I am greatly interested in all of this and will test ideas but that
will take time. Just expressing an opinion but if I started forging
an ingot I wouldn’t stop until I had at least a 20% and maybe closer
to 30-40% reduction (depends on the alloy) or it was obviously work
hardened well (it should be ringing good). These are speculative
specifications I am extrapolating from experience in parallel type
work. I could be wrong, I would have to do it for myself to give
better numbers, and I will sometime.
I have question on all this. What size ingot do you work on and do
you use an anvil, T-stake, or some other surface for forging? Is it
flat or slightly curved (my choice for break down)? I also wonder
what the out come would be if I forged and then milled the ingot? Do
you forge your ingot right after pouring or do you anneal it first?
What do the Mokume guys do? Has anyone forged all the way to a
finished sheet? Was it usable for severe forming?
I am able to easily roll out fine finished stock with a beautiful
surface finish and strength, using relatively simple studio
techniques. What am I doing right??
As I recall the original discussion was concerning rolling out 12’’
sterling sheet from ingot. If I’m wrong I am very sorry. It is easy
to roll out small thin ingot of the 1/8’’ to 3/16’’ sorts for small
sheet. The shear forces and problems are present but the size of the
job small enough to keep them from emerging.
Once you work with larger ingots, sheet and a power rolling mill any
small problem can not remain hidden. I didn’t take the time to state
that most of my experience is with sterling and though I have enough
experience with all alloys except Platinum my references mostly
apply to sterling. We are considering the change over to Argentium
right now.
I am puzzled by the problems you suggest with crystal structure,
grain boundaries, as well as oxygen absorption causing failures in
rolled out ingots.
Often I have observed that when presented with the problems
associated with rolling (larger work now) one of the approaches
taken is too anneal to often and too hot. This enlarges the grain and
equalizes the stresses but it also encourages absorption is
atmospheric gases that damage the alloy (again sterling). The
results is the next couple passes seem fine but the cracking,
shearing, and other problem are back in force. The metal is damaged
and will need to be cleaned before reuse.
There is a very considerable difference in rolling as the size
increases which I thought was the direction of the discussion. I
wouldn’t hesitate to roll smaller ingots without milling or any
thing other than cleaning. Unless the subsequent forming is severe
(our shops speciality work is in drawing, forging, rolling, and
coining) you will not have any problem at all. Try going wider than
4’’ with a finished product of 1/8’’ (.125’‘) and your problems mount
quickly. Go to 6’’ even more so! 12’’ is going to be very difficult;
I have never worked a 12’’ line and don’t expect to any more; I only
hope someone does.
I really liked the online discussion I followed and hope to check
out another in the future; timing as always is the problem.
I was always taught to do the first couple of passes from cast
ingot by way of forging them down with a hammer.
I, too, have learnt it that way. The next important thing to my
master was the annealing frequency: How much rolling before one has
to re -anneal. For example:
Silver 925: 70%
Silver 800: 55%
Gold, Yellow 18kt: 65%
Gold, White 18kt: 65%
Gold, Yellow 14kt: 55%
Gold, White 14kt: 55%
Gold, Yellow 9kt: 50%
Gold, Red 9kt: 55%
So rolling down Y9k goes like: 10…5mm 5…2.5mm 2.5…1.25mm etc.
Sterling is 10…3mm 3…0.9mm etc.