Grain Mill roller spacing

[RuddyCrazy]

G'day Guy's,
I'm on the way to getting my AG setup going and scrounging thru some bits in my shed I found a couple of spur gears and some 1-1/2" solid steel shaft. Now after working at a flour mill I found with the rollers going at slightly different speeds is the best way to get the crush and the 2 gears I found suitable have a difference of 3 teeth so that will give me the speed difference needed. Now from what I've seen on You-Tube video's with grain mills a diamond knurl is machined onto the rollers. Now I do have both diamond and straight knurls here so it's a toss which one to use.

Now for the question..... what clearance between the rollers is deemed the best, as I do feel if both rollers have minimal spacing the grind will be too much and there would be a good chance of the lauter tun clogging up. I'm guessing about 0.5mm but eh thats my guess so what is the spacing you guy's use on your mills as I would like to get it right first time.

Cheers Bryan

[warra48]

A number of thoughts:

1. We are not making flour. Our objective is to crush the grain to a sufficient level to allow water access to all of the grain internals and enable the enzymes to work at converting starch to sugars.

2. It is preferable to keep the hulls as intact as possible to aid in draining and lautering. This is particularly so if you brew with a 3 vessel set up. Apparently it is of some lesser importance if you plan to brew with the Brew In A Bag system. Obviously, running the two rollers at different speeds will probably lead to tearing or disintegration of the hulls. It is possible to add rice hulls to act as a replacement and to assist the process.

3. I run one of the original MillMaster mills. The rollers are geared, but they are geared equally. The rollers are knurled, in a diamond pattern. It would be my preference.
To what extent unequal gearing may cause a problem, I don't know, just suck it and see, it may cause none.

4. For my system, I run my gap at 1.1 mm, and this setting always delivers over 90% extraction efficiency for me.What works for you will need to be worked out by you by way of trial and error, but I suspect 0.5 mm is probably too small a gap.

[RuddyCrazy]

Hi Warra,

Thank you for the quick reply mate and I went backup to the shed and found a matching 30 tooth gear to suit the larger gear. These gears are from a change gear set of a swiss lathe and are surplus to my requirements so with the gear being a nice coarse mesh I will have a bit of leeway on adjustment. Measuring the centre distance I still have a couple of mil to machine off the shaft so next step will boring out some plates to fit the bearings then the grain mill will start to take some shape. As we're off the grid here I'll do the milling up in my shed and make a variable speed DC drive and use a 1/2 hp 50 DC motor to drive it with the power coming off my shed battery array.

The next quest will be finding some old pub kegs to modify for my HERMS setup and later this week when those DS18B20's arrive I'll start working on the code for the pic micro I'll use as the brains behind the setup.

Cheers Bryan

[squirt in the turns]

Sounds like you're on your way to a sweet system, Bryan.

Mills with geared rollers (as opposed to one roller free-spinning and relying on friction with the grain to turn it, I suppose) often list reduced shear and tearing as selling point, so I'd say going with the matching gears is a good call. Sounds like you've got a nice workshop set up... if you could build in some way to easily adjust the gap à la the MashMaster MiniMill, you'd be able to change it up as required.

As Warra states, the objective is really just to crush the grain enough to get the sugar out. Milling it finer can increase your mash efficiency to a point, but can also lead to a stuck mash (including a stuck recirculation in a HERMS), and/or more turbid wort, which can lead to more trub loss, which in turn might hurt your overall efficiency.

[Guru]

Sounds like an interesting project Bryan, make sure you put up some pictures when you have this (hopefully) working.

[rotten]

The monster mill I just bought quotes a gap of 0.045". Visually it's a bit smaller than my old marga (actually not mine anymore) although the crush tonight looks to have left more husk in tact-ish, go figure. The proof will be in the beer pudding.

[emnpaul]

The monster mill I just bought quotes a gap of 0.045".

Which is a fraction over 1.1mm for the imperially challenged.

My Barley Crusher mill is .9mm peak to peak (checked with a feeler gauge) on the diamond knurling. I'm not sure if this is what qualifies as the "gap" or if it is an average based on the pitch of the knurling.