Tunning a Grain Mill

I just purchased a Millar B3 grain mill. I haven’t used it yet but it has a nice roller adjustment feature. The problem is I don’t know what to set it to. What is a good starting point? How do you know if its the right setting? Suggestions??


You will probably get a lot of answers but here is mine. I just got a new mill and I asked the guy at the home brew shop and he said they set trees to .040 I never had a problem with their crush so I set mine at about half way between .050 and .025 so that’s about .037 I believe.

.035 is a good starting point. Your gap has a lot to do with your system. If you BIAB you can crush much finer. If you fly sparge you will likely need a coarser crush. I would start at .035 and brew a batch and see how it goes. If your efficiency is low tighten the gap a little. If you experience a stuck sparge loosen the gap.

Do you know what setting the manufacturer delivers it with? It’s probably a good starting poiint.

I have mine set at .032. I started out at .028 because someone else who BIABs told me that was their setting. My efficiency was very very high. I’ve been opening it a bit since trying to dial in efficiency to 80% for more consistent predictable results.

At .032 I still get most kernels broken into 3-4 pieces, a good deal of flour and mostly intact hulls.

The tighter your crush the higher your efficiency but depending on how you mash you could get a stuck sparge if you crush too hard.

The manufacturer doesn’t have it set when its delivered. There is a numbering system from 1-5. I will have to see if I have some gauges and set to around 1/32 and see what number corresponds to that gap. Thanks for the input!

If it doesn’t come set and you don’t have feeler gauges use a credit card. They are.030 thick.

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So, used my new grain mill for the first time and missed my OG by 10 points. I usually don’t have a huge problem getting close to my intended gravity. The only variable that changed was the mill. I set the gap with a gauge to .032. Its a Millar B3 grain mill and .032" corresponds to the ‘2’ on the setting dial. I can get it tighter. Now that I think back before the mash it did look a little course but i thought it was ok. I didn’t think it would make that big of a difference. Any advice on this mill or gap? Is there a way to judge the crush other than brewing with it?

It was an IPA. Was shooting for 1.066 came in at 1.054. 15 lbs of Rahr Pale Ale (SMaSH with simcoe). 6 gallon batch. Mash for 60 min at 150 deg. End running was high at 1.028.



Post a picture of your crush?

Crush is the biggest factor in efficiency, so it is no surprise that using the new mill changed your efficiency. Set it a little tighter and try again.

FWIW, I have mine set for 0.029" and typically get efficencies of 78-80%