KYM hand grinder adjustment nut not working

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
brammetje

#1: Post by brammetje »

Dear home-barista's,

I've been reading lot's of articles on your website for years and it's time to make an actual account. I have been making espresso for multiple years, first at work (just our coffee room) with a Rancilio midi and then at home with a La Pavoni Espresso plus lusso (pressurised) and now with an ECM boticelli and an OE Pharos grinder. I want to start making coffee at work with my La Pavoni and a vintage hand grinder (it has been un-pressurised), which is why I bought a nice KYM grinder.

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Unfortunately I have an issue with the grinder I have recently acquired. When I bought it, I actually managed to make an espresso with it, so I'd won the vintage grinder lottery so to speak. However, when I was polishing it I realised I should take it apart a little bit and unfortunately something went wrong.

I tried taking the adjustment nut off completely and it wouldn't come off. Of course I found out there wasn't a reason for releasing it at all, but I only figure that out after trying to take the nut off. I am now unable to set the grind coarseness. The middle part (the centre of the four fins) doesn't rotate while I'm rotating the nut (see the figure for the part I'm talking about). What happens now is that I rotate the nut and after about half a turn it sort of skips. It is caught in a loop and I can't get it tightened or loosened. Just applying pressure on the nut while trying this didn't solve it unfortunately. If I do that you don't feel the skip, but I'm still not getting anywhere. Because I don't really know how it worked in the first place, I don't really know what to do.

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I have three questions:

1. How is this mechanism supposed to work? What exactly is supposed to be moving and what isn't? Should the centre bit be attached to the nut?
2. Do you have any idea how to get the nut to move properly again?
3. Is this part fairly universal for KYM grinders? In other words, can I just buy another random KYM grinder and change the part?

Hope you can help me!

User avatar
cuppajoe

#2: Post by cuppajoe »

If the wheel turns, but not the shaft, then it needs to be re-staked to the shaft. Staking is using a bluntish punch to drive the wheel and shaft metals together. If you look close at the top, you can see how it was done originally. Don't use anything sharp, to avoid cutting the metal.

When I redo one of these I usually start by soaking the metal parts in JoeGlo or other coffee detergent. Coffee oils is probably what is locking things up. Also, usually there is a ball bearing in the well of the burr where the shaft impacts it. If missing, you'll never get it to adjust properly. If the detergent doesn't do the job, see if rust is a problem. You should not have to use force to get it to turn. A small dab of food grade grease on the shaft and ball is advisable.

Nice little grinder, they usually do a good job for espresso.
David - LMWDP 448

My coffee wasn't strong enough to defend itself - Tom Waits

brammetje

#3: Post by brammetje » replying to cuppajoe »

Thanks a lot for the reply. I'll soak it in the next couple of days to test this. I did have to apply quite a bit of force initially to get it to turn, but then it turned reasonable smoothly until the point where it's now stuck. I suspect that I separated the shaft from the wheel using that initial force. This also suggests that my shaft itself is stuck and I'll see if I need to use any other solvent to dissolve the old grease in there. The ball bearing is still inside, and is actually stuck in there, probably because of the old lubricant/grease.

I think it's best if first I take it all apart and then try reattaching it. I'll keep the topic up-to-date when I have tried your suggestions :)

brammetje

#4: Post by brammetje »

cuppajoe wrote:If the wheel turns, but not the shaft, then it needs to be re-staked to the shaft. Staking is using a bluntish punch to drive the wheel and shaft metals together. If you look close at the top, you can see how it was done originally. Don't use anything sharp, to avoid cutting the metal.

When I redo one of these I usually start by soaking the metal parts in JoeGlo or other coffee detergent. Coffee oils is probably what is locking things up. Also, usually there is a ball bearing in the well of the burr where the shaft impacts it. If missing, you'll never get it to adjust properly. If the detergent doesn't do the job, see if rust is a problem. You should not have to use force to get it to turn. A small dab of food grade grease on the shaft and ball is advisable.

Nice little grinder, they usually do a good job for espresso.

Thanks! I managed to get the shaft connected through the wheel. I ended up using an old screwdriver. Unfortunately I haven't managed to centre it properly, so I still can't grind espresso. In any case, this problem has now been solved. Thanks!

User avatar
grog

#5: Post by grog »

Yeah, I always found the most difficult part of reassembling these old hand grinders was getting the burr set re-aligned so you don't have a 'skip' during the grinding rotation. Some burr sets are easier than others to get back in alignment.
LMWDP #514