My beloved rolling mill is having a really bad day. Somehow, the rollers
became out-of-parallel. It is a Cavallin that I have had for several
years, and I haven’t had a problem until today. I can’t imagine that
annealed copper could have caused this problem and I am not big enough to
"lean" on it. I am at a loss as to how to remedy the problem, having
received no instructions with the mill when I purchased it new. And, what
my common mechanical sense is telling me to do doesn’t seem to be
possible.
How does one recalibrate a rolling mill?
Laura Hiserote
i have cavallini rolling mills too.
what i usually do every now and then to keep them ‘parallel’ is to pull up
and out the cross bar handles and adjust the rolls by hand with the two
graduated discs on top. i turn them both down until the rolls touch
perfectly, then i insert the handle again.
Most often rolling mill have 3 gears (2 large, 1 small with a handle) on
top that are turned to adjust the spacing between the rolls. The small gear
with the handle can usually be raised so it no longer meshes with the 2
large gears.
What usually happens is the center gear (small 1 with the handle) is
raised until it doesn’t mesh with the 2 larger side gears. Then, when it’s
re-meshed with the larger gears one of them is turned a few teeth out
off position. This results in that end of the roller being higher or lower than
the other.
The easiest way to get the rolls back to parallel is to remove the small
gear. Now turn the larger side gears individually until the rolls contact
each other over their entire length. (If the rolls are completely open,
each side may have to be partially closed before the rolls can be entirely
closed.) When the rolls are in contact with each other over their entire
length, the small center gear should mesh with both side gears.
If this doesn’t correct the problem, one of the large gears may have
slipped on the screws that control the roll spacing. This isn’t very
probable since most times the gears are keyed to the adjusting screws &
can’t slip.
I missed most of this thread so I hope I’m not repeating what someone else
has said, but you can buy a “feeler gauge” at an automotive supply store
to calibrate your mill with. This gauge has a bunch of steel “leaves” of
varying thicknesses - i think they use them to gap spark plugs usually -
i think. But you can bring the rollers of the mill real close together and
then run one of these leaves thru the gap. It should run from end to end
uniformly - if you feel it hang on one end, you know you need to adjust
parellelism. I think I’m making it sound kinda complicated but it is real
easy to do when you have this gauge and they only cost a few dollars.
My beloved rolling mill is having a really bad day. Somehow, the
rollers became out-of-parallel.
Hello Laura:
On the top of the rolling mill, find the center turn gear that you use to
adjust the thickness of the stock you are rolling needs to come off. It
either slips right off or a “C” clip must be removed. You can then freely
turn the 2 gears that adjust the distance between the rollers. Turn them
both down until the rollers touch evenly all the way across the roller
surface. Re-install the center turn gear.
a “feeler gauge” at an automotive supply store “leaves” of
varying thicknesses - i think they use them to gap spark plugs usually
the spark plug gauges have a calibrated wire at the end the type you are
describing are used for point adjusment (almost obsolete) &/or valve
adjustment. brass is also available meant for magnetic pick up adjustment
in distibutors available in metric or english . also plastigage might
be of use for someone this is a little plastic strip that crushes out to a
certain width, comparing the width of the strip with a printed scale
defines the clear space between two metal objects. original usage is for
main bearing clearances :
I calibrate my Durston as follows: 1) close my rollers until I can just
see light through the 2 rollers. 2) Pull straight up on the tightening
crank to remove it. (This should be pretty standard on all mills.) 3)
Hand turn the right or left side needing adjustment. 4) replace
tightening crank. Good luck
Wondering, why wouldn’t one be able to do this with sheet goods (be they
silver or whatever) . . . wouldn’t, say, 20 G be a good guide???
Not really.
FWIW
Using this technique you can’t guarantee the accuracy fo the mill setting
2E Sheet & wire are not always rolled/drawn to the correct size.
A more accurate way is to use a set of feeler gages. Feeler gage sets
usually have gages from .001" to .035" thick. If a size is needed that’s
not in the set, 2 or more gages adding up to the desired thickness can be
used. Feeler guages are made of hardened steel & are very accurate. The
cost about $10 or less/ set.
Another way is to use a micrometer or caliper (on cabable of measuring to
2E001"). Measure the thickness of the sheet/wire to be rolled, close the
mill 1 turn, roll a short section. Measure it with the mike or caliper, the
difference between the 2 numbers is the amount of closure per turn of
the screw. Note this number for future reference. It’s a simple matter now of
determining how many turns or parts of a turn the mill must be closed to
get the thickness desired.
Most shop use of rolling mills doesn’t require the thickness accuracy that
sheet & wire suppliers do. It is good to know though, how much you mill
closes for each turn or partial turn of the adjusting screw.