Grain crush and mash efficiency

[Bubbles]

Cheers J, will do.

[Bubbles]

In case anyone else finds this useful, this BYO article states that a drill-powered mill will make your grain crush more fine, if anything. Interesting.

A second variable affecting your crush is the speed that the rollers rotate. The rollers on hand cranked mills rotate much slower than the rollers of commercial mills. (Their average speed is 400 RPM, for the optimal 9.8 inch (250 mm) diameter rollers). As such, hand cranked mills crush more coarsely when set to the same gap size. In contrast, home malt mills powered by a portable drill greatly exceed the proper speed and may crush too finely.

[Will_D]

Just remembered I have a RPM meter!

Checked my Hitachi Rechargable drill and on low speed it is running 300 RPM!

This is what I use.

High speed is about 1200

Now the drill states 400 and 1500 so maybe my old meter needds calibrating but you get the idea Low speed on a 2 speed drill should be perfect!

[Bubbles]

Well, I examined the mill at the weekend and it seems that I hadn't pushed the hopper fully home in the recess in the board. Though I'm not sure if that could account for the coarse crush.

So I set out a bowl of pre crushed maris otter from the hbc and adjusted the rollers in an effort to get something similar. Here's the HBC grain:



My first attempt sheared the husk a little too much so I tightened the rollers back a bit.



Here's the final crush:



It's finer than the HBC grain but it should be coarse enough to prevent a stuck mash and I'm hoping that it will improve my efficiency somewhat too.

If the gauge on the rollers are any guide I'd estimate the gap width to he around 0.045". Though Ciderhead is giving me a loan of feeler gauges (ooh-er..) so I should be able to confirm the width accurately when I have these.


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[Ciderhead]

1-1.1mm, a credit card is about 0.9mm.

[DEMPSEY]

1-1.1mm, a credit card is about 0.9mm.

And to test it use the wife's credit card at 0.8mm 

[Bubbles]

1-1.1mm, a credit card is about 0.9mm.

How does the final crush look to you? coarse enough?