So your diamond disk isn't running quite the same anymore and you're ready to toss it out the window?
Don't count it out just yet. There is a way to "re-dress" an electroplated disk to get the most possible life out of them.
If your disk is running too slowly for your pieces, try this: With your grinder turned off and unplugged, place your disk on the wheel head. Pour some water and a little dish detergent over the top of it (this helps break up the surface tension).
Next, take an aluminum oxide dressing stick and grind with it on your disk (WITH THE GRINDER OFF!), from the center of the disk to the edge of the disk and back like spokes on a bicycle wheel. Do this all the way around the disk.
Plug your machine back in, turn it on, and wash the diamond disk down thoroughly with clean water. Your disk should now run almost like new, but for a much shorter time.
What's happening is this: As you use the new diamond disk, you are grinding on maybe 20% of the tallest diamonds, this makes the disk very very aggressive. As time goes by, they slowly break down and you begin to grind on more and more of the diamonds until eventually they are supporting the glass more than grinding it.
When you dress the wheel, you are effectively "breaking off" some of the diamonds, creating an uneven surface again. Microscopically, you are now grinding on fewer of the diamonds again.
Of course, you now realize, this is also a very destructive process on your diamond disk since you are destroying some of the diamonds. This is why you do not want to try this process until your disks are not performing well at all. This is mainly a stop gap measure in between receiving new disks and needing to operate with the old disk. You can repeat this process on the disks as needed, but we've found that it taps out at about four dressings with each dressing being substantially closer to the previous one time wise.
Once you get to a point of dressing your disk and it no longer affects it's grinding ability, you've just created a large abrasive refrigerator magnet. Go get a new disk.