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WTB - Grain Mill

Discussion in 'Buy and Sell' started by Bob65, 11/2/20.

 

  1. wide eyed and legless

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    Posted 14/2/20
  2. wide eyed and legless

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    Posted 14/2/20
    Double post
     
  3. Meddo

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    Posted 14/2/20
    Yeah OK, looks like a straight knurling rather than the more common cross/diamond knurling. Was thinking of wider cut flutes rather than knurled flutes. No biggy anyway, just curious (and apologies if my terminology is out of whack, I don't have any experience in the machine shop).
     
  4. wide eyed and legless

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    Posted 14/2/20
    Yes, cant get straight knurling, as the roller is turning in the lathe and the traverse of the tool couldn't make it possible. Unless someone could enlighten me any different.
     
  5. Meddo

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    Posted 14/2/20
    Apparently you can but I haven't bothered reading how it's achieved. Here's a description of the kompakt that mentions cut-knurling:

    The main characteristics of MattMill Kompakt include

    • hardened and cut-knurled steel rollers with a diameter of 70 mm
    https://www.kraushaar-exports.de/mattmill-kompakt/
     
  6. wide eyed and legless

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    Posted 14/2/20
    OK probably explains why he made the rollers 50 mm wide, and used a 50 mm wide tool.
     
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  7. Hangover68

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    Posted 15/2/20
    You could use a shaper to cut horizontal grooves in a cylinder or a multi axis CNC machine.
     
  8. wide eyed and legless

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  9. Jack of all biers

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    Posted 16/2/20
    If we go to the German text the above translation 'cut-knurling' comes from, we find the word fräsgerändelte. Broken down, essentially fräs (from Fräser meaning 'milling cutter'), gerändelte (past tense meaning - having been straight-knurled {rändeln is the root word here meaning straight-knurled specifically} ). The term 'cut-knurled' is likely used because of the type of machine tool or cutting bit used by Mattmill to make the knurling (cut knurling apparently does a higher quality knurl than other types). So cut-knurled is the method used to make the straight-knurling on the Mattmill Kompact.

    Re the words Knurled or Fluted - Let's look at the English meanings.
    Knurl : a small projecting knob or ridge, especially in a series around the edge of something.
    Flute : a rounded shallow concave groove on the shaft of a column, pilaster, etc

    Note the difference in the above. Flute = rounded/concave groove (nothing to do with the ridge). Knurl = small knobs or ridges (can be rounded or not). So if the 'fluting' isn't concave or rounded in some way, it is not 'fluting'. Knurling can be fluted or not, but knurling is always small.

    The word knurl can mean something is fluted, even in another language. The word knurl in German (transitive verb) has a few different words that can be interchanged depending on what is done. Knurl can translate to - Riflen (groove/channel/rifle/serrate/flute), kerben (groove/notch/nick/cut a notch in [something]), zacken (notch, indent, serrate, tooth [something]), rändeln (straight-knurl) or kordeln (knurl especially diamond-knurl).
    If something is fluted, in German it is geriffelte (grooved/fluted/knurled/serrated/ribbed/checkered/finned), ausgekehlt (channelled/grooved/fluted) or kanneliert (fluted)

    Now why did I explain the above. Well in part to back up that Mattmill have described their surface as straight-knurled (not fluted or fine fluted), but also to show why there is such confusion in the use of the words. Remember, if it's small and raised just off the surface, it's knurled. If it's not small, it's something else. However, we often come to the vernacular use of words, so sometimes fluted is not fluted (see below).

    I've looked at my Mattmill straight-knurling and can't see any concaveness nor roundedness in the grooves. Don't forget the knurling is there for grip, especially to get the passive roller moving, so that the husk doesn't slip and get torn. The Mill Master info states (I have never used one) the 'saw tooth fluted rollers' are for a cutting purpose. I note they state the 'flutes are angled' and the close up pics don't indicate there is any rounded or concave grooves, but that could be explained due to semantic drift....

    Keeping things on topic, I can recommend the Mattmill, though like all mills, it should be run at specifications and speeds that the manufacturer recommends. For example, the Mattmill is recommended to be run under 300 RPM (though I find slower than 100 RPM gives a better result in the mash/lauter) and I understand the Mill Master can be run much faster without shredding the grains (likely as much to do with the geared rollers than the 'saw teeth' on the rollers) . The advantage of the Mattmill is the obvious quality of its construction, as well as the angle that the grain enters the gap that will reduce husk shredding (at the right gap setting and mill speed). In my use of it, that has been the case. My general range of mash efficiency went up from HBS crushed grain (circa 75-80% conversion efficiency) to Mattmill crushed grain (by hand - circa 92-97% conversion efficiency) (with drill - 85-89% conversion efficiency).

    Both Mattmill Kompact and Mill Master appear to be made with quality materials and attention to quality manufacturing technique and were the two that I short listed for quality and durability.
     
  10. wide eyed and legless

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    Posted 16/2/20
    Straight knurling, so it can be done on a traverse, but not at a great length, I would have thought one tool at a 50 mm width but 50 mm is doable with small straight knurling tool. Very educational.
     
  11. MHB

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    Posted 16/2/20
    Pretty much where I got to after looking at the options. I would probably give the edge to the Mill Master as it has two driven rollers, but the MattMill has bigger rollers - meh too close to call.
    Will be interested in hearing how the diamond coated Keg Land mills go. Looking at it there are some very clever features and some complete dross (so often the case with new products from either of the "Keg -" people) for me the one big concern would be what happens in a couple of years time (will the plastic retain strength), imagine dropping a nut or even hard stone into the mill, (commercial mills all have magnets and de-stoners built in) will it disassemble it self and send several kg rollers flying around the shop? Has happened with much bigger mills with fatal results. The Idea of a home size wet mill has some appeal.

    Went and had a flick through relevant section in Kunze, the main points to consider are: -
    Feed Rate - How fast the malt enters the mill, all commercial mills have a feed control of some type.
    Distribution - Malt should be presenting evenly along the length of the rollers (often part of feed rate control)
    Rotational speed - Kunze talks about speeds between 250 and 440 RPM, but presupposes that all rollers are going to be bigger than about 250mm in diameter (work it out in surface velocity). Lower speeds for pre-crushers or 2-Roller mills, faster for following roller pairs (in a 6-Roll mill, 3 pairs) it might be 1st pair 250RPM, 2nd pair 250-280RPM, 3rd pair 280-300RPM, faster for special mills. Slower for smaller rollers (much slower!)
    Gap - well obviously that plays a part.
    Few other factors that play a role, but most of these are going to be outside the scope of home or even small craft breweries.

    No matter what sort of mill you choose (there are better and worse options) if you have a play around with your gap, rotational speed and feed rate you will be able to get the most out of your malt.
    If you aren't a BIAB brewer, its well worth thinking about double cracking, fist a coarse run (>1.3mm) then a finer finishing run, will give you bigger husk fragments and finer endosperm kibble with little flour.
    Means higher yields, faster lautering/recirculation, lower tannin extraction...

    On fluting/knurling larger/commercial rollers are centripetal cast high hardness alloy steel, the fluting is a cold ground spiral at a pitch of (Kunze) 4-14%, there are also a bunch of flute shapes and different rates of rotation and orientation (too complex for me - leave it to a mill engineer).
    Mark
     
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  12. Grmblz

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    Posted 16/2/20
    Please sir, my head hurts, can I go home now. ;)
     
  13. MHB

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    Posted 16/2/20
    Take two beers and call in the morning
     
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  14. Jack of all biers

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    Posted 16/2/20
    Agree, the geared rollers are an advantage on the smaller diameter rollers as well as enabling a bit more speed. The saw-tooth 'fluting' is an improvement on the previous diamond knurling by all accounts too. The larger rollers are an advantage for better draw resulting in less husk damage/cutting, but only at slower speeds (IMO, cause their not geared).

    I see the KL Maltzilla as having some better features (in built motor), but some cheaper less durable components. The unique thing about the Maltzilla is the diamond surface for longevity of grip combined with the 70mm diameter rollers. It will be interesting to hear honest feedback about the milled grist performance from users (I fully expect improvements in efficiency/lauterability). The slightly confusing thing (and amusing I must say) is that much is made of the longevity of the surface that grips/draws the grain through the mill, but the rest of the mill does not appear to be made of long lasting componentry. I could be wrong and if one treats ones tools right they will always last longer, but plastic is plastic. On the face of it, it appears to be a good cheap entry point motorised mill, with some good qualities (especially the price), but I see it failing the OP's criteria of
     
  15. The Flyingscrapyard

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    Posted 16/2/20
    Knurling is produced by pushing a pattern into the metal, rather than cutting one in. The normal diamond knurl is formed by two different hardened rollers (1 x LH & 1 x RH) mounted in one tool holder and it is pushed into the metal being knurled to a depth that creates a pointy top to the knurl.
    At this [point, the lathe saddle is put into a slow feed and is slowly traversed along the job to essentially "mash" the form of the two rollers into the surface. There is a displacement of the metal, with the root of the knurl being a smaller diameter than the parent metal, and this is pushed up to a diameter greater than the parent metal.
    The straight knurl on grain rollers is not generally a knurl in the normal sense, though you can get a straight knurl (wheel studs being a classic example). The straight flutes are often formed by a gashing tool in a metal planer (look it up), a metal shaper, a milling machine with a tool to cut each flute, a cnc lathe with a milling head, or a hobbing machine. If you had a gear planer or gear shaper, you could also do the same with these if they have enough travel to cover the length of the roller being cut.There would be specialised machines out there that would do this quite quickly because that is all they are designed to do. Quite interesting to see being done.
     
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