I've been learning on the Darex E90. It's very easy to use, but it took
a while to figure out exactly how to adjust the stylus height and
position vs. the wheel location in order to duplicate the original
factory primary relief angle on a given cutter.

However, that took all of about an hour of learning time. The
instructions really have all the information you need, but they're not
that well organized or written and the pictures are small and blurry, so
you have to jump around in the document to collect all the pertinent
points.

After having reduced one old 3/4" cutter by about 16-thousanths in
diameter, I had figured out what I needed to know. About the only thing
I really don't like about the machine is that it takes a steady hand to
uniformly draw the cutter flutes along the length of the grind. There
will be a simpler mechanical method in the works as soon as I have had
the time to work it up.

The stone I received was an aluminum oxide cup, and the type 11 cups they
use are cheap in Al2O3 (about $30 for the same size and rim thickness as
the Darex stock wheel). The 11V9 CBN wheels are expensive from Darex,
and (apparently) cheap from import suppliers. But like all things, you
get what you pay for.

The Darex CBN cup has about 3/8" of usable matrix on it. The import
wheels have about 1/8". The Darex wheel is roughly 3X the price of the
imports. OK... 3X the life, 3X the price. It's a no-brainer to go with
the Darex wheels, because they are the right matrix concentration, right
resin, and right configuration to use on the machine. I will buy one
Darex cup and one import to compare them. Darex, $240, import, $70.

The sharpening process is simple, once learned. It takes less than two
minutes to set up and grind the primary relief on a 4-flute, 4" long
(cutting length) cutter. The face takes about the same amount of time.

For me - in my situation - this will be a boon. Now, I don't have to
stock a 'large' number of cutters. If I happen to dull a one-off I need
to finish a job, I can take the five minutes off it takes to tune it back
up. In the meanwhile, since all my milling IS what could be called
"utility" cutting, the edges are plenty nice enough. I don't own an
optical comparator, but do have a microscope. When time permits, I'll
try to visually compare the edges. But they look and feel very nice, and
I can feel fairly small imperfections. I know it will save me money on
new cutters every time I use it. I'll let you know more when I get the
CBN cups.

The balancer they supply is nitzy to adjust; It's just a washer, and
there is no "adjustment" per se. You just diddle the washer around with
a prying tool until you're happy with the feel of it. But with only a
little work you can get that thing to the point where all you feel is a
trace of hum in the chassis. Remember, you can only balance the grinding
cup, not the motor itself. But for what it's worth, without the grinding
cup installed, you can barely feel the motor running. So, they must've
made Baldor "super-balance" the motor. A strobe light and a magnifying
glass might help to get it just right.

I also got lucky. I didn't notice in the original offering, but the
Darex diamond dresser accessory came with it. It's barely worn, having
more than 3/4 of the original length of diamond tip still remaining.
It's apparent the original owner didn't use it much, because the wheel
had badly rounded-over edges that required quite a bit of dressing to get
sharp again.

LLoyd