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Stone in my grinder!

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  • Stone in my grinder!

    I've been home roasting for a year now and it had to happen- a small piece of gravel size stone got into the grinder (a robur)
    The robur hiccuped and I turned it off straight away, stone was visible in two pieces in the top of the blades- couldn't get out without removing blades. Blades look ok, and all seems to be grinding ok now- but I have that doubt in my mind if there has been some hidden damage to shaft or motor.

    Anyone else have experience with this? I've given some beans away to friends who use sunbeam 0480- I imagine a stone could do big damage to one of them?
    Any ideas about how well destoners work as the source of my green beans is happy for me to use his, but hasn't been an issue til now.

  • #2
    This is a link to the thread regarding a home-made low-budget de-stoner. Depending on the amounts you are supplying to friends (it wont be suitable for large volumes), this may be an alternative to borrowing your green suppliers one. Many of us have been caught out, and it could wreck your friends grinder, depending on what the stone is made up of.

    Or you could get a proper "bought one" from Andy. See BeanBay.

    Last edited by GrahamK; 11 June 2014, 05:41 PM.


    • #3
      Only one in 12 months? ;-)

      There is more here in this thread.

      Stones are common enough, the real meanies are quartz, and one or two black hard little bean shaped stones that I've found

      Then there's the steel.......... thankfully I haven't found any.....yet.

      De-stoning is crucial, especially if you're supplying friends or in business. The cost of one Robur is only

      marginally less than a CS stainless steel whizz bang destoner. And if there happened to be more than one grinder go down

      in the same batch of coffee. 8-o ..... that doesn't bear thinking about.

      My hope is that if I miss a stone one day it's a massive uncut pink diamond, then I can chuck the grinder away

      and just keep the stone! ;-D


      • #4

        There is not a week that our destoner doesn't spit out a few. The larger ones qualify as pebbles.

        Our booty also includes: screws, nails, paper clips, staples, glass and a drop earrring


        • #5
          Looks good the one on bean bay- I assume they only work on roasted beans- you can't destone green?

          I've had lots of stones but this is the first to get past my beady eyes !


          • #6
            Your assumption is correct. The beans need to be lighter than possible foreign objects.



            • #7
              Hi tannin et al.

              Being "old school" I still run a (very) strong magnet over every batch of green beans. I had quite a collection of metal before I did a cull of all unwanted coffee items & "accessories". My PB is a rusty 5/8 BSW nut, just like we build conveyor belts and bridges with. Actually, it may have been harmless simply because I have never seen a grinder aperture big enough to swallow it!

              A stone will often choke a grinder without too much damage, however a metal nail or staple gun staple... final grinder curtain call.

              Very easy to get the magnetic stuff out before it gets into the roaster, which is not to say that checking for stones & other misc bits "post roast / pre grind" is not also a good idea.



              • #8
                Thanks for info- my robur has the little magnet in the hopper- but it's never found anything- probably doesn't do anything. Good to know I probably haven't killed my grinder- I want it to last 20 years :-)
                A Destoner is a must for me now.