Posted Tue Aug 21, 2012, 3:55pm Subject: Attn: Hand Grinder Users - Simple mod
I posted a brief mention of this over in the massive "Hand (grinder) Jive" thread on HB, but thought it was deserving of mention here as a separate topic.
Short story for those who can't bear to read through – try replacing the steel ball in your lower bearing (if you've got one) with a ceramic ball – now you can either read on, or go experiment.
I recently picked up a KyM grinder here on BST, and, while the wood was perfect and burrs were sharp, it had some issues with very hard turning and a horrible squeaking noise. Figuring that the ball bearing was missing from the lower bearing cup, I decided to order some potential replacements. While I was at it, I figured that I'd get ceramic, rather than steel, balls, as I've experienced the improved performance in bicycle hubs from swapping ceramic in for steel.
Interestingly enough, the original steel ball wasn't missing, but was simply frozen in place with accumulated coffee tar. I discovered this after soaking everything in Cafiza for an hour or so to clean it up, then drying out the bearing cup with a cotton swab. After a few spins that kept bring out more gunk, out came the swap with the ball, embedded in coffee tar, stuck to the end. So I had cleaned it and reassembled with a dab of lubricant then used it for a week. The grinder worked very nicely indeed, grinding more than fine enough to choke both the Caravel and the NS Ellimatic without burr touch.
Before I discovered the wayward steel ball, I had ordered some Al2O3 (aluminum oxide ceramic) balls in several sizes, based on guessing from the internal diameter of the bearing cup on the lower burr strap on the KyM. The 4mm size is the one that fit mine. I dropped it in, put a dab of Dow 111 on the end of the upper burr shaft that seats agains the ball, and reassembled.
I hadn't expected so large a difference. Much smoother action that spins much more freely. I seem to be able to get the burrs closer without touching, which suggests the steel ball wasn't perfectly round. It feels as if less effort is required to grind, though that doesn't strictly make sense. It is grinding finer and more evenly.
So, if you've got a hand grinder sitting around that has a lower bearing cup with a free-floating ball bearing, you might want to give this a try. At under $2 for a high-grade ceramic ball, it's certainly cheap enough, and it might make your favorite hand grinder just that much better. I got mine from VXB, who fulfill through Amazon if you pay through Amazon, and gladly sell you single balls rather than multiple packs if that's what you need.
My next step will be to check if I can make the same mod to any of my other grinders.
ThomasP Senior Member Joined: 23 Aug 2012 Posts: 1 Location: Intermountain West Expertise: Just starting
Posted Thu Aug 23, 2012, 10:11am Subject: Re: Attn: Hand Grinder Users - Simple mod
Thank you for the info on this. I have a Zass knee grinder I bought about 5-6 years ago after their long hiatus. I don't know if it has the lower bearing cup but it might be worth checking into if it makes that much of a difference in grind. I've always been happy enough with it's grind for a moka pot. Thanks again for the info!
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