Is it normal for the top roller of a rolling mill (Durston
mini-mill, in this case,) to disengage when the rolls are opened far
apart? I am rolling down some silver ingots, one of which was about
1 cm thick. As I opened the mill rollers there came a point where
the top roller stopped moving - so only the bottom one is pushing
the ingot through, which is not working very well. The rolls weren’t
anywhere near their furthest spacing.
Before I disassemble the mill - or melt & repour the ingot - does
anyone have insight into what’s going on? Thanks in advance.
At one time I was looking a making my own rolling mill, but I ran
across a less expensive version and bought one instead. Now I just
make my own rollers, actually, I have made 2, but I figure if 2 came
out ok I should be good on any others I choose to make.
Rolling mills have two gears which engage, one on the lower and one
on the upper roller that is what makes both rollers roll at the same
rate. When separated farther than the gear teeth can touch they stop
rolling together. The Durston has a cover over these gears, I have
one of the cheaper varieties and there is no cover on mine so I get
to see the gears work. There is nothing wrong with your mill, you
have just separated the rollers to far apart for the teeth to engage.
If it has not happened to you yet, sometimes the teeth on these gears
hit dead on and you can’t get the rollers to go back together, simply
turn the handle while you bring the rollers back together and you
won’t have that problem.
The gears on the left side of the picture are for increasing the
torque of the crank handle and the small ones you see on the right
are the gears that make the rollers work together. When you opened
yours up, the 2 gears on the right separated, and the top roller
stopped rolling. The bottom roller is the one, gearing wise, that is
directly connected to the handle on yours and mine.
Hate to say it, but for my two cents, re-pour your ingot or hammer
it down on an anvil.
It’s very simple, and completely normal. If you look up inside, near
the crank, you will see the two gears that drive the rollers. You
are opening the rollers to the point where the gear teeth are no
longer engaging. Regardless of how far it appears the rollers will
go, it is the gears that give the maximum opening, in reality. You
can do various things, but I just pull out the big hammer and smash
down the ingot until it will fit…
Most small studio rolling mills including most of the Durstons only
support rolling materials that are about 6 mm thick so at 1cm you
are way over its capacity.
James Binnion @James_Binnion
James Binnion Metal Arts
You guys are awesome. Thanks for the explanation, and you know, I’ve
tried hammering the little sucker down as thin as I can (annealing
and all,) but it’s just taking too long, so it’s a remelt for me and
no ingots thicker than 5 or 6mm from now on.
I've tried hammering the little sucker down as thin as I can
(annealing and all,) but it's just taking too long, so it's a
remelt for me and no ingots thicker than 5 or 6mm from now on.
Get a bigger hammer. Your metal will be much higher quality if you
forge it down 50% before rolling.
Jim
James Binnion @James_Binnion
James Binnion Metal Arts
I’ve tried hammering the little sucker down as thin as I can
(annealing and all,) but it’s just taking too long, so it’s a
remelt for me and no ingots thicker than 5 or 6mm from now on.
Get a bigger hammer. Your metal will be much higher quality if you
forge it down 50% before rolling.
This is just my urge to kibbitz, cuz this is not my area of
expertise, but I’ll go out on a limb…
I feel reasonably sure you don’t have to forge your ingot cold. When
I took a mokume gane workshop, we heated out billets to red, then
quickly went to the anvil and whaled away on them with a big sucker
hammer. The metal moved very quickly while hot, and we reduced the
billet pretty quickly from maybe an inch and a half to where it
would fit in the mill.
I was a bit sore after this whole enterprise, but it was actually a
lot of fun to forge that billet down. It helped, though, to have a
partner to hold it (with tongs) and flip it so I could use both
hands on the big ol’ hammer. On the other hand, your ingot is
probably small enough to do alone. What do the experts say? Any
reason not to hot-forge the billet?
Sterling must be forged at a black heat or you risk cracking it.
Also small ingots can be quite tricky to hold on to when hot forging.
But yes you can reduce a billet or ingot while hot much faster.
Jim
James Binnion @James_Binnion
James Binnion Metal Arts
Don’t know what the original metal referenced here is, but forging
red-hot sterling can cause the metal to “hot short”, resulting in
cracks in the billet. Only forge sterling if it is black-hot.
dear Linda, yes, that is normal, I have made many ingots that
disengage the top rollers. if you look at the side of your mill you
will notice that it has springs in it.(i do believe) the mill
actually opens up alittle more when you roll somthing through. try to
forge the ingot on an anvil, annel it then forge again until it fits
without a problem. caution…once apon a time i was in the studio
of a friend of mine and i rolled an ingot through a mill and
literally split the mill in half. Durston is one of the best on the
market but you do have a mini mill.