Is modifying the corona mill necessary?

Hey all,

I just scored a free corona mill, and many people here have modified the end of the screw by threading it with a die. This allows a nut to be screwed down on the grinding plate and lessening the wobble.

I bought a tap and die set, and after multiple attempts, I simply cannot get it started. The die doesn't even scratch the cast iron.

The instructable on this topic states using a 1/2" die, and but I have not had any luck.
So the question: Is this mod necessary? I'm a Biab brewer, so my crush will be fine... Will the pressure of the grains being extruded keep it from wobbling and affecting the crush?

i use the cotter pin in mine, and i mash in a cooler. Personally i dont think its necessary to thread that, the grain should get a pretty uniform distance between the plates. Some need some washers to space the plates but that is mill to mill.

Thanks!

It is not you, cast iron is difficult to thread. Plus, a 1/2 -13 thread takes much effort. You could practice on a piece of 1/2 inch dia aluminum rod which is about the softest there is, then mild steel, then your mill.

Before doing any mods, try running a pound or three through the mill and see if you like the results. I have read that BIAB is very forgiving of chopped or fine grain. Normal sparging depends on whole husks to act as a filter bed.

I didn't have to tap mine. I just found a bolt that would go through the existing hole. No biggie.

Getting the washers set up right took a bit of doing, but once I got it, it was good to go for a good many brews.

And of course it's a very good idea to find a threaded rod to replace the handle so you can run the mill with a drill instead of the handle.

KramE said:

The instructable on this topic states using a 1/2" die, and but I have not had any luck.

Click to expand...

Got a link, I am curious? Sounds oprtional to me as most users don't do this?

Found it...I kind of disagree with this, easier and also effective is to free up the burr plate and let it wobble, the grain will even it up as you mill .

Thanks for the replies. I'm glad it's not terribly easy to thread cast iron.

Wouldn't it be better to have a little wobble? As a coworker pointed out, the screw and plate could have easily been casted as one piece.... So why didn't they? His guess is that without the wobble or some kind of pressure relief the screw or plate would snap under pressure.

There is at least one such case here on HBT that a threaded screw did break

KramE said:

Wouldn't it be better to have a little wobble?

Click to expand...

Quite possibly...but you need the wobble to have a full range of motion, sometimes the cotter pin is so large and bent that the grinding plate is bound up and crooked to the shaft and the other plate, rather than try and fix the two plates true, if one is free to move it will position itself with the pressure from the grain.

While that machine threading looks great, I'm not convinced that it would hold the grinding burr true to the other grinding burr...I would just make sure that the grinding plate has range of motion and it will find the sweet spot as you tighten the gap. Cheers!

Thanks again!

I didn't have much trouble using the 1/2" - 13 die recommended. I got a 1" hex die held with a 1" crescent wrench. I used a ratcheting socket to drive the auger through the die using the 1/2" bolt in other end of the auger. Once I had the die facing the right way so that the wider opening was up, I didn't have much trouble at all.

a lot of people see the wobble and know that its bad on a roller mill so they invent a way to "fix" the disk mill.
push some grain through it and the wobble stops. adjust it as necessary. A fixed mis-aligned disk is much worse than a wobble that doesn't matter.

I didn't do anything to mine and it works fine. If you are concerned about shredding the husks, just look into malt conditioning. Or add rice hulls.

Didn't have to tap mine. I just found a bolt that would go through the existing hole. No biggie.

Getting the washers set up right took a bit of doing, but once I got it, it was good to go for a good many brews.

And of course it's a very good idea to find a threaded rod to replace the handle so you can run the mill with a drill instead of the handle.

+1 to all of the above, also conditioning your malt with the corona produces a much more consistent crush I have found.

I welded mine, no wobble and it mills grains like a champ. I BIAB and always get outstanding efficiency.