Corona Corn Mill, with grain mill plates - flour mill

I am proud to present some info on the Corona Grain Mill that my parents passed along to me.

They were "back to the earth" folks in the '70s.  So I got loads of books, and some pretty cool toys.

The Corona Grain Mill is still sold, designed for crushing whole corn kernels into polenta or corn meal.
There are retro kits available to turn the corn mill into a grain mill.
I have the Retsel wheat grinding plates, without the alternate auger.  
The auger you can buy with the replacement plates is designed to deliver smaller grain more evenly and slowly to the plates. It is not entirely necessary, though I don't know how much it helps.

Pictures to follow.

Here you are.

Please note that the plates are held on with a nut. This is not stock, or even the retrofit version.
Later post will explore and provide links / info.

Looking for ways to change the cotter pin retainer from the original corn cracking plates, I found an Instructable which suggested my fix.
Asked around with machine shops, and found one that charged me 15 min work for using a die set to thread the outside of the auger.

Link to the Instructable website (awesome, thank you!): The Major Mod - thank you dlewisa from Instructables
You will notice the original corn cracking burr plates in the pictures.
And the threads and nut retaining the plates.
When not using the bolted-on corn burrs, but using the retrofit grain plates, the nut lands just near the cotter pin holes.
Best to have threads just a bit past the cotter pin holes to allow full tightening.
They used 1/2" 20 thread. Very common standard and plenty fine enough to maintain tightness.

Pictures below.

From the Instructables page referenced above: machine-threaded auger end and how it fits together with the original corn burr plates.

Two pics.

The first shows the surface where the end of the auger had to be machined with a Dremel tool to get the plate to ride evenly - perpendicular to the auger.
The little blocks which lock into the plate do not extend far enough to knock the plate off-kilter.

The flat surface, out of which the threaded section and the blocks project, is the interface surface.  
It took some very small grinding/polishing with Dremel, checking frequently by full reassembly, to make the plate ride properly.
Still best to check adjustment with every use.


The second picture shows how the nut tightens down just a bit more than where the cotter pin is designed to sit.

If you look back at the very first picture I posted in this thread, ...  found it?
OK, see how the two grain grinding plates are really close?  That's the whole point.
I don't want to eat GRIT from the plates clashing - but I DO want finely ground flour.

So the only other thing that can keep the plates out-of-parallel is the way the fixed plate is mounted.
This is all rather roughly made stuff, because remember, the Corona is an inexpensive corn-crusher, not a precision grain mill.

So the Retsel plates are also not 100% perfect.  Nor is the way they are held in with thumb screws.
This part is a matter of making sure you know which way the plate sits better, then taking it out, and gently adjusting the mounting wings to twist it into true.

IF I can make picture show this part well, I'll post them.
Wish me luck.


Here's hoping this is helpful.
And BTW, if you are looking for any of these things, here are some links that may help:
DuckDuckGo search for "retsel corona"
Retsel's grain plates retrofit, though many other places sell similar
Corona grain mill site, complete with operators instructions and parts list

Great post Trevor!  We have our corona mill from those days also and it has been put to constant use for most of that time.  I don't grind wheat anymore, but use it several times a week for buckwheat, sesame seeds, flax seeds and oatmeal(for flour).

This grinder is one of the few kitchen tools that I still have from the early seventies....wonderful that your parents had theirs to pass on to you.  

Thanks so much for all of the pictures and links...I'll be spending some time browsing them.

Great post thanks! I have a corona but find it a pain to mill corn in it, but easy for buckwheat. BTW, what is the material of the corona is it alu?
In short words: you gave us a description on how to fix retsel burrs in the corona to get fine meal without the metal??

Judith Browning wrote:I don't grind wheat anymore, but use it several times a week for buckwheat, sesame seeds, flax seeds and oatmeal(for flour).

Cool!  Thanks Judith.
I have got to try some other grains, and see what they do.
Too many recipe books and ideas, too little time.  

Angelika Maier wrote:Great post thanks! I have a corona but find it a pain to mill corn in it, but easy for buckwheat. BTW, what is the material of the corona is it alu?
In short words: you gave us a description on how to fix retsel burrs in the corona to get fine meal without the metal??

Thank you Angelika!
Yes, grinding wheat or corn does give the arm a workout.  There are beefier mills, and some electric ones that are (i'm sure, not from experience) bound to be cake to use.
I'm a fan of doing thins the hard way. Just how I am .

Yes, your "in short words" is exactly what I intended.
The amount of arm strength and effort is pretty high, still.  Perhaps the alternate auger makes it easier.

With a little practice using the current setup, I have discovered NO grit in the resulting flour.  And it is slightly more fine than the store bought whole wheat I have on my shelf.
A little rough grind actually leaves a nice texture for pancakes and such.  Up to cooks preference for a dish - nice to be able to choose!

The practical method I used this last go round was to adjust plates to JUST smaller gap than the wheat berries.  So they all get cracked.
Throw out the first several ounces first go after the retro fit.  There may still be likely loose grit on plates.  After this, the only reason to waste product is if the grinding plates clash by human error.
Before the last of the grain goes through, feed a little of the first run flour in, and slowly tighten the plates as you turn the handle.  JUST A BIT
You'll find the "perfect spot" where plates don't clash, grinding is not impossible, and the result is pretty darned professional quality.

My last batch of flour could pass through the sifter about 50% from the first grind.  I actually prefer it finer than that for bread, so it all went through three times as I CAREFULLY adjusted the plates tighter each time.
Rather eat a slightly rougher grind of flour than munch on bauxite.

Yeah, it is work.  As I said, I like to do things the hard way.  

BTW, what is the material of the corona is it alu?  

From Coronamill.com

Cast-iron construction for durability
Tin-plated steel—no aluminum parts!  

I think the "grit" I have found was from two places:
1. the hardness of wheat berries when using the (incorrect) corn burr cracking plates
2. the (correct application) bauxite grain stones clashing due to poor mounting with only a cotter pin  ...   thus this thread


I just hope something here is useful to somebody. I love reading other peoples experience so I don't have to learn through pain same as they did.      

I am looking to get a grain grinder but don't know the first thing about them. I want a hand crank, I won't need much at a time and then don't have to worry about the power. I don't want to buy the most expensive, but I don't want to buy a cheap one that is just throwing money away and frustrating me  

Can you give some recommendations? Thank you

Howdy.
I bought this new in 1976. I grind my own corn that I grow, wheat, sesame seeds, sunflower seeds, peanuts, even coffee(now I have a coffee grinder). 2 sets of burrs and also a stone(for fine flour). I don't even change the burrs any more. This is solid cast steel, not aluminum. The hand crank is stamped "made in poland". This was purchased from  Nelson and Sons, Inc, 525 south 500 West, Salt Lake City, Utah. They don't seem to be in business anymore. There is a Nelson and Son grain mill on ebay right now, but only with one set of burrs.

Thank you

Heres one listed as meat grinder. This is what I have, OB made in Poland.
https://www.ebay.com/itm/221886931752?hash=item33a97de328:g:sIwAAOSwyvBV-HC9

That is certainly in my budget.  Does yours grind fine enough for flour?   Thanks

Howdy,
Yes. It may take more than one time thru, to grind finer. You can sift out the grits and regrind. It will take some trial and error to get the settings right. It is a workout for me, takes some getting used to, hand grinding.Nuts and seeds are easier. I make sesame tahini, sunflower, almond.peanut butters. I will fine grind poppy seed for pastry. They are very handy and a good workout. When I have stale corn chips, I grind them up with corn and make corn bread. I bought mine in 1976, $35.45.