Of course the first thing I did was pull it apart to see how it worked and what could be done to improve it.
What I did notice when I had it apart was the way the bottom washer of the thrust bearing seemed to bear on both the white plastic support ring and a shoulder on the drive shaft. This seemed to defeat the purpose of having ball bearings to take the rotating load and replace it with higher friction sliding surfaces at the shaft shoulder and/or the outer plastic support ring. It could also result in the plastic support wearing down over time and making grid adjustment vary. I figured that the easiest way around this was to enlarge the centre hole in the bottom thrust washer so that it would fit over the shaft and enable the ball bearings to take all of the load and transfer it directly to the support ring.
I have drawn a rough sketch to illustrate what I am talking about by showing the cross section of the bottom burr arrangement-
I proceeded to enlarge the centre hole in the bottom thrust washer using a conical grindstone in my Dremel as it was made of hardened steel which could not be drilled out.(Warning - gets very hot to touch!)
From memory, extra shim washers were needed under the burr to get the grind fine enough, but, when re-assembled, the grinder worked a treat and showed no signs of 'settings creep' the whole time it was in use.
When I eventually replaced it with a K3 I gave it back to the original owner who has since loaned it to another friend (who is currently using it with one of my 'spare' EM6910s which I have loaned him and says I'm not getting back
) So it's certainly done some work and still seems to be fine.The second grinder modded in this way was an EM0450, bought at an op shop by my wife for $10, and labelled as "won't grind fine enough". This seemed to work OK after the treatment but has been relegated to the entertaining area outdoors and has not seen a lot of work. From memory I did not have spare shims, so used a thin card disk between the black plastic cup assembly and the top steel thrust washer.
Then came the 'Pay it Forward' special. I'm not sure what had happened to this but the bottom thrust washer was badly cupped with 6 dents in it from the ball bearings of the thrust bearing.
Figuring that this would not do wonders for the grind quality I went hunting in the washer tin in the shed and found an odd shaped hardened steel washer about the right diameter, but thicker than the original, and with a square hole in the centre. Once again, using the Dremel, I managed to enlarge and round the hole to fit the shaft. When re-assembling it I found I had no spare shims so found a suitable washer which I ground down almost to the right thickness on an oilstone - with it the burrs just touch at about the "8" setting so I will either reduce it further on the oilstone or get some more shims when I get time.
One other point before I finish and that is concerning 'end play' in the shaft. On one of the machines I found that I could almost completely remove this by juggling shims and packing but am not sure how much difference it would make to the grind quality - open to experimentation.
Well, as you can see, my experiments have not been very controlled but seemed to yield some promising results for improving the performance of these grinders. If anyone tries something similar with an old grinder I would like to hear your results.

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