GGs:
  A quick perusal of the gold-standard Baldor line-up finds a dozen grinders
that run 1800 rpm and spin wheels 8" or 7"---these range in price from about
$600 to just under $1300, so it's all academic, ain't it?  A good mandrel and
motor set up is the way to go.  You can get down pretty low with a pair of step
pulleys; I used to run one with two 10-inchers (at about 200 rpm if I did the
math right, anyway) VERY slow! Took a good while to grind really hard tools---
like Witherbys---as you might have guessed, but it was so docile, and non-whiny
that it was a real pleasure; the extra time was actually a bonus.
                                              it's not raining, but we know the
roof leaks, so I'm heading up...gam in OlyWA/USA

http://www.baldor.com/catalog#category=31
 

How horrible it is to have so many people killed!---And what a blessing one
cares for none of them!
Jane Austen

      From: scott grandstaff 
 To: porch  
 Sent: Sunday, February 18, 2018 9:44 PM
 Subject: Re: [OldTools] What is a good slow speed grindstone
   
Guess I'll weight in with old school, even if you don't want to hear it.

I grind steel. I have been grinding steel for a long time.
I don't just mean grinding a bevel on a 1/4" chisel. I mean making a 
1/4" chisel
or any other size I like, from scratch. Or grinding other tools or 
knioves or machine parts, whatever i want or need to make from metal.

    Grinders 8" and under run at 3600. This is standard and has been for 
generations.
10" is better because they take it down some.
But the surface speed is not terrible dissimilar.