[redrocker652002]

My wife was nice enough to buy me a grain mill for my birthday. It is a 2 roller Hullwrecker. I do BIAB and from what I have been reading the crush size should be somewhere near .025. Does that sound about right? I am going to try it with my next brew and am looking forward to it helping me gain some efficiency and consistency in my brews. Once again, any input is most welcome. Rock On!!!!!!!

[denny]

The only way to know is to crush some grain and try it.

[Kevin]

There is no real "should be" gap size. There is only "what works for you". I would set the rollers at around .028 - .030 to start with and see how that works out. You can begin to decrease the gap from there if you wish. I can tell you that personally, with the bag I used and the size of the mesh that .028 worked best for me.

[redrocker652002]

Awesome, thanks guys.  I will start with .028 and see how it goes.  I am guessing the only real way I will know is when I am done and the OG is either what my software says or better, right?  Can I just take a pound or so, experiment with the crushes and do a stove top experiment that way? 

[denny]

Awesome, thanks guys.  I will start with .028 and see how it goes.  I am guessing the only real way I will know is when I am done and the OG is either what my software says or better, right?  Can I just take a pound or so, experiment with the crushes and do a stove top experiment that way?

The crush is dependent not only on the grain, but on your equipment.  Testing it on different equipment might not give you a true picture.

[Megary]

Awesome gift from your wife.  Having your own grain mill is definitely a big step towards consistently hitting your numbers.

I agree with Kevin that there is no magical gap size, you just have to try one crush, crush finer, crush finer again, step it back…until…Boom!…You’ve got the crush that works best for you.  Then you can forget about it.   

Best advice I got for my simple BIAB set up was “crush til you’re scared”!  Good luck.

[Semper Sitientem]

And if you haven’t thought about it already, you’ll want to remember to charge your drill in advance. After using the hand crank once, you’ll realize what a PITA it is. I have a Hullwrecker and my first experience was in a hot garage.

[redrocker652002]

Thanks for all the input.  I have a multi battery setup by Riobi that uses the same battery for multiple tools, so I always have 4 or 5 batteries at the ready.  LOL.  I am going to try and hand crank the first time just to make sure I get the grain nicely crushed.  But, who knows.   Something else to learn.  LOL.

[BrewBama]

Mill gap is worth some research. The efficiency difference between a wide vs tight gap is a $1-$2 cost to a homebrew batch so that’s not a show stopper. But there are other considerations outside cost. You can use a feeler gauge, I use a No 14 sieve.

This is how I found my gap:

I did this by setting the mill at a certain gap, milling 100 grams of standard pale malt, placed the milled grain on a No 14 sieve, shook it side to side for 15 seconds – tap, shook it back and forth for 15 seconds – tap, and repeated this for 3 minutes. I weighed how much was left on top of the sieve and how much was sifted into the paper plate beneath it. Then I brewed a batch.

I ended up with a balance sweet spot between good extract and good recirculation. X% remained on top of the sieve and Y% fell thru. I marked my progress on the side plate of the mill.

This is one of the things I learned that Summer I brewed the same Pale Ale substituting hops to discern their flavor much like the Single Hop Experiment beers at MoreBeer.

Now, I am beginning to think there are impacts of milling beyond efficiency or the issue of a stuck lauter. I have been brewing session beers lately and it seems the recipes I have researched would indicate the weight of grain the author suggests would yield a much higher ABV on my system. That suggests, among other things, that their mill is not set as tight as mine therefore requiring more grain to get the OG. Attenuation and as a result FG may be impacted as well.

“some contend the quest to eek out a few extra gravity points may actually decrease wort and, consequently, beer quality.” - M. Schott

[erockrph]

When I was using a 2-roller mill and brewing BIAB, I settled on 0.88mm as my gap. Since all my feeler gauges are covered in machine oil, I decided to use guitar picks as feeler gauges instead. I don't think there was anything special about that gap setting, to be honest. When I got down to Tortex Green, I was hitting 78-80% efficiency reliably, and my beers tasted good. I decided to stop fidgeting at that point, and I just kept a pick with my mill to be able to spot-check my gap easily.

For BIAB, I'd start with a fairly tight gap as long as your husks aren't getting all shredded up. Then brew a few batches and pay close attention to your efficiency. If your happy with how your beers taste and the efficiency numbers you're getting, then you can either stick with that gap or decide to make an adjustment and see how it affects your beer.