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Rolling Mill - Am I doing it wrong?

Jewelry Discussion
#1

! Rolling mill question this time. Everytime I take a perfectly
straight piece of metal to texture in my rolling mill (or wire for
that matter) it comes out “curved” like a very slightly “c” shape.

Am i squishing it to much too soon? Or do I need to actually spring
the good bucks for a quality mill? Mine is one of those cheapie
chinese ones. Wanna make sure before I drop any more $$$ on
something. I am just using a thin piece of homemade paper on top of
the metal to texture it.

Advice?
R/Kennedi

#2

You may have already had many responses to this, but probably the
distance between your rollers are not quite even, so one side
compresses the metal a bit more and creates a curve. It is worth
spending time running (inexpensive) pieces of metal through, and
adjusting the rollers till they are exactly aligned.

Good luck,
N. Katsu

#3

Hi,

Could be your platens are out of alignment (not parallel) and
therefore not exerting equal pressure across the breadth of metal
being processed. Regards,

Kofi

#4

Hi Kennedi,

Could be several things.

Most likely: Rolls are out of alignment. Does it curl the metal when
you just roll metal by itself? If so, it’s the rolls. Easy (ish) fix.
(To the extent it can be fixed. If the mill itself is junk, you may
never get it perfect.) I did a thing for my website way back, so the
instructions for leveling out your rollers are here:
http://www.ganoksin.com/gnkurl/33

Next possible culprit: the laws of physics.

Unless you’re using one of the steel pattern rolling plates, the odds
are pretty good that you’re going to have uneven thickness of 'stuff’
to roll. More ‘stuff’ equals more stretching of the metal under that
area. Which means it expands more, and causes the rest of the sheet
to curve away from that area. You can actually take a straight piece,
and turn it into an “S” just by having more stuff on the right at the
bottom of the sheet, and more on the left at the end. (Take a look at
my explanation of how the metal curves in the ‘realign your rolling
mill’ link above.) Same idea: the sheet curves away from the area
that got squished most. More thickness of paper to pattern with more
squishing, and more curving.

Roller printed metal never comes out perfectly straight if you do
anything serious with it. Which is why you always want to pattern a
piece larger than you plan on using: to make sure you have enough to
cut your finished piece out of, regardless of how it bends.

Regards,
Brian.

PS"> you shouldn’t be rolling wire on the flat rolls of a mill,
especially a quality product of the Middle Kingdom. You’re likely to
crush a print of the wire into the rolls. They’re case-hardened, and
the increased PSI (by way of reduced surface contact on round wire)
can get over the pressures needed to deform the cased layer.

You can hammer it mostly flat, and then use the rolls to even it
out. That’s OK. But I always do that over against the very edge of
the rolls, just in case it does print. That way the rest of the roll
is still useable.

#5

Either the material is not uniform in thickness or your rollers may
need aligning. This can be done with a set of feeler gauges. Look on
line for instructions, then try it out with a piece of scrap or
copper. Rob

Rob Meixner

#6

If you mean the metal curves as if you were curving the sheet thats
what they do. If the metal is curving to the right or left as it
comes out of the mill the rollers may be a little out of alignment.
Close the rollers almost closed with just a paper thin space and look
between the rollers the space you see light through should be even
all the way across. If its not you can adjust by lifting up the
adjustment handle on top until it is not engaged with the side gears
then manually rotate one of the side gears til the light space is
even then push the gear back in place. You may have to move side
gears just a hair for the teeth to fit. If this doesn’t work you may
have to make you metal slightly wider then you need and trim the
edges

#7

The answer depends on which axis the curve is in. Is it to the right
or left, or up or down. In the case of the former, the answer has
been given: on side if the rolls are closing more than the other.

#8

Noralie- Before you tear your rolling mill apart… Even with
perfectly straight rollers I can make a piece of metal curve just by
inserting it in at an angle or ever so slightly instead of dead on
straight or by pushing or pulling on the side of the metal as I am
rolling it through.

Have fun and make lots of jewelry.

Jo Haemer
timothywgreen.com

#9

Jo,

Thanks for the (I don’t own a rolling mill,
unfortunately. I use one at the art center where I take classes) It
never occurred to me that putting the metal in at an angle would make
it curve - Duh! We share the classroom with other classes - one of
the first years we came back from the summer break to find that a
child (I hope) had run play doh through the gears. So we don’t have
much control over the settings, although no more play doh, thank
goodness.

I love the classes, the teacher is a sweetheart.

Noralie

#10 
you shouldn't be rolling wire on the flat rolls of a mill,
especially a quality product of the Middle Kingdom. You're likely
to crush a print of the wire into the rolls. They're case-hardened,
and the increased PSI (by way of reduced surface contact on round
wire) can get over the pressures needed to deform the cased layer.
You can hammer it mostly flat, and then use the rolls to even it
out. That's OK. But I always do that over against the very edge of
the rolls, just in case it does print. That way the rest of the
roll is still useable.

I wish I had known that a long time ago as I rolled some 10 gauge
copper wire through my mill and now I have a groove in the rollers.
Nobody believed me that it was only copper wire but no steel has
ever touched the rollers. It seems to me that if the rolls were
case-hardened, the copper wire should not imprint in them. Thanks
for this update and I will not do that again.

What upsets me is that I had a little cheapie mill before getting
the big boy Durston and nothing seemed to bother the rollers of the
cheap one.

Oh well. live and learn.

Thanks for posting this Brian. It is very helpful.

Lona

#11

Hi Lana,

Case hardened rolls are sort of like… Ho-Ho’s. Hard skin over
soft squishy core. (relatively speaking) Depending on how thick, and
how hard the cased layer is, you can get enough PSI from wire to
either deform the core by way of pressure transmitted thru the case,
or get the case to crack, like the chocolate skin on a Ho-Ho. The
thicker the case is, the better, but that takes time to create (and
thus money, of course). It also depends on how many times the rolls
have been reground. They typically only have cased layers .050" o
r.100" (at most) thick. If you end up grinding off .015" per
re-finishing, that can get pretty thin, pretty quick.

You can have the rolls on your mill re-ground. That’ll get the wire
print out, but expect to pay $100-200 or so. (You’re looking for a
machine shop that can grind “between centers”, to about a 5 micron
finish. Do not let anybody talk you into ‘centerless grinding’.
That’ll wreck your mill. If you decide to do this, drop me a line
directly, and I can explain what to ask for when you talk to the
machine shops.)

Now that I think of it, I know Matthew Durston occasionally reads
the Orchid list. Matthew, if you’re reading this, how thick is the
cased layer on your rolls? (I suddenly care, because I just bought
one of your big D-54’s…)

Regards,
Brian

#12

I did a lot of research a couple years ago before buying my Durston
mill. I don’t recall any prohibitions specific to rolling round wire
on the flats or copper wire. That being said, I have a small copper
track on one of my rollers. It doesn’t appear to be a deformation,
but rather a stain. I have been able to almost compliantly polish it
out with simichrome polish. I store my mills (I also have an economy
model), well oiled after each use with an old pillow case over them.
I rarely roll sheet, but will start forging my wire a bit flat before
rolling it. I will assume that Durston monitors this board and if
there is something wrong about what we are doing, they should chime
in. Buying a rolling mill, especially a Durston mill, is a major
milestone for many of us. I will add that I am less than impressed by
Durston’s lack of follow up to several questions that I have asked in
the last year both of them and their local (USA) distributors. Just
my two cents. Rob

Rob Meixner

#13

I have seen this type of pink on the rolls before. I did it on my
mill. One thing that can cause the copper “Strip” on the rolls of
your mill can be dirty or wet metal. Running metal that is slightly
wet, or that has any residue of pickle on the surface can cause
plating on the surface of the rolls. It can be similar to
contaminated pickle that plates that nice pink color on your silver.

Drop some steel wool into your well used, blueish colored pickle,
and thendrop some silver in and see what happens. The same thing can
happen to your rolling mill when there is a little pickle on the
surface of your metal and it comes in contact with the rolls. These
rolls are not stainless steel so they can rust and be quickly
attacked by acids and other contaminants that are present in our
studios.

Luckily, it sounds like you caught it in time to avoid any major
etching problems.

If you have any other questions on your mill, please let me know.

Best regards,
Phillip Scott
Rio Grande
1.800.545.6566