Regarding nomenclature, my wife came up with SAFT. Don't know if you were sentient in 1971, but many of those of us who were will remember the radio theme song from the movie "Shaft", so SAFT is easy to remember. And, of course, it's close to soft, and it has the A in it. Ergo A is soft, therefore Z is hard.
I had been getting more and more frustrated trying to get a decent finish. Yesterday I balanced the wheels and wrapped a sheet of paper around the wheel adapter spindle before installing the wheel (to keep it located radially). I carefully dressed the wheel and then did a grind on my test part. YUK! Worst finish yet, by far!
I went to bed thinking "It's spindle bearings. That's why they sold it to you, dummy!"
Today, calm and in my right mind, I decided to do a rough test to see if the wheel was unbalanced. I put a glass of water on top of my wheel guard and let it come to rest with the spindle on and wheel mounted. The water sad dead flat. OK, I can't be that far off.
Then, in order:
inked up the periphery of the wheel
dressed doing 3-2-1 (.003" then .002" then .001") no ink left
broke the leading edge with a dressing stone
knocked off the "hangers" with a piece of wood
took a cut between 1.5 and 2 thou, horizontal speed on 24, crossfeed .016"
then took a cut 0.3-0.4, horizontal speed on 12 crossfeed .050"
then did a sparkout pass, horizontal speed on 12 crossfeed .050"
finish MUCH better
My operating theory is that I hadn't been dressing enough off the wheel to get it really trued up.
The wheel is a 46H aluminum oxide, vitrified bond, somewhat open matrix, made by Radiac.
This is on a KO Lee 718 grinder from just about when that movie Shaft came out.
If you have any suggestions as how to further improve the finish, please post them. I know this is a very commonly discussed topic. I did spend about 3 hours reading previous posts on the subject.
metalmagpie