Followup on the Darex E-90
 

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

Followup on the Darex E-90
 

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
.70...
..

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.


You might contact Jeff Toycen, his wheels are fantastic and were much
cheaper than Darex... if you talk to Jeff and don't learn something; you
weren't listening: http://cuttermasterprofessional.com/SC2012.pdf

Followup on the Darex E-90
 

"David Courtney" fired this volley in news:jojjdm
:

You might contact Jeff Toycen,

Thanks! I will.

Lloyd

Followup on the Darex E-90
 

"David Courtney" fired this volley in news:jojjdm
:

wheels... were much
cheaper than Darex...

Maybe "were"... not now. A few bucks more, now.

But I'm sure I can learn from him, even at that.

LLoyd

Followup on the Darex E-90
 

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
.70...
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.

0.5" times the sine of 1 degree is about 0.008", so for a flat-cutting
cup or dish wheel you lower the finger below the tool's center height
by 0.008" times the angle times the diameter of the cutter. Lowering
the spring finger 0.040" rotates a 1" cutter by 5 degrees (close
enough for mental math and cutter relief).

For a round wheel you leave the finger at tool center height and raise
the wheel 0.008" times the relief angle, times the wheel diameter.

jsw

Followup on the Darex E-90
 

"Jim Wilkins" fired this volley in news:jojkk6$pod$1
@dont-email.me:

0.5" times the sine of 1 degree is about 0.008"

Thanks, Jim. The trig I can do, but that goes in the archive, because it
saves me a LOT of math. G

Lloyd

Followup on the Darex E-90
 

"Jim Wilkins" wrote in message ...

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
.70...
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.

0.5" times the sine of 1 degree is about 0.008", so for a flat-cutting
cup or dish wheel you lower the finger below the tool's center height
by 0.008" times the angle times the diameter of the cutter. Lowering
the spring finger 0.040" rotates a 1" cutter by 5 degrees (close
enough for mental math and cutter relief).

For a round wheel you leave the finger at tool center height and raise
the wheel 0.008" times the relief angle, times the wheel diameter.


With the Darex, you ALWAYS leave the finger at cutter centerline when grinding your primary--in order to change relief angle, move the entire finger assembly left or right along the keyslot, this changes the point along the helix where actual contact with the wheel is made in the axial plane; moving it left increases clearance; moving to the right decreases it, the actual amount being co-dependant on individual cutter helix angle and effective wheel diameter. ( the air bar height is fixed, at a position appx 3/8 below the cup center line )

Only place I can think of where the above doesn't hold true being with straight flute ( non-helical ) cutters.

Followup on the Darex E-90
 

"PrecisionmachinisT" wrote in message ...

"Jim Wilkins" wrote in message ...

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
.70...
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.

0.5" times the sine of 1 degree is about 0.008", so for a flat-cutting
cup or dish wheel you lower the finger below the tool's center height
by 0.008" times the angle times the diameter of the cutter. Lowering
the spring finger 0.040" rotates a 1" cutter by 5 degrees (close
enough for mental math and cutter relief).

For a round wheel you leave the finger at tool center height and raise
the wheel 0.008" times the relief angle, times the wheel diameter.


With the Darex, you ALWAYS leave the finger at cutter centerline when grinding your primary--in order to change relief angle, move the entire finger assembly left or right along the keyslot, this changes the point along the helix where actual contact with the wheel is made in the axial plane; moving it left increases clearance; moving to the right

( correction--moving it left DECREASES clearance angle, and to the right INCREASES it )

decreases it, the actual amount being co-dependant on individual cutter helix angle and effective wheel diameter. ( the air bar height is fixed, at a position appx 3/8 below the cup center line )

Only place I can think of where the above doesn't hold true being with straight flute ( non-helical ) cutters.

Followup on the Darex E-90
 

"PrecisionmachinisT" fired this volley in
:

With the Darex, you ALWAYS leave the finger at cutter centerline

According to Darex, 0.010" below center.

Lloyd

Followup on the Darex E-90
 

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 3.70...
"Jim Wilkins" fired this volley in
news:jojkk6$pod$1
@dont-email.me:

0.5" times the sine of 1 degree is about 0.008"

Thanks, Jim. The trig I can do, but that goes in the archive,
because it
saves me a LOT of math. G

Lloyd

When I set up my surface grinder to sharpen lengthwise flutes I adjust
the spring finger (hacksaw blade end) to a protractor beam or angle
block that crosses through the tool's center axis at 5 degrees from
vertical.

jsw

Followup on the Darex E-90
 

"Jim Wilkins" fired this volley in news:joju7l$li3
:

When I set up my surface grinder to sharpen lengthwise flutes I adjust
the spring finger (hacksaw blade end) to a protractor beam or angle
block that crosses through the tool's center axis at 5 degrees from
vertical.



Just thinking about the geometry -- placing the stylus 10-thou below the
cutter center allows for a slightly lesser relief on large diameter
cutters, and slightly more on smaller ones. I figure that's what Darex
intended. They built the trig into the machine.

LLoyd

Followup on the Darex E-90
 

"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 3.70...
"PrecisionmachinisT" fired this volley in
:

With the Darex, you ALWAYS leave the finger at cutter centerline

According to Darex, 0.010" below center.



Perhaps--my maing point being that once it's been set, basically you don't
fiddle with it.

Followup on the Darex E-90
 

On Fri, 11 May 2012 12:15:50 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

I've been learning on the Darex E90.

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).
LLoyd

What size grit and what letter of hardness do they use in their
aluminum oxide wheels?

Followup on the Darex E-90
 

Followup on the Darex E-90
 

On Sun, 13 May 2012 16:22:03 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

fired this volley in
:

What size grit and what letter of hardness do they use in their
aluminum oxide wheels?


Not a clue, yet. I haven't investigated it. I will, of course.

Lloyd

I look forward to hearing from you and others. I have a Weldon
fixture for my KO Lee and have been wondering what wheels others who
do their own sharpening use (other than CBN, which is expensive)

I haven't been overly successful at gashing the ends for center
cutting. If you master that, you'll have to let us know how you do
it.

Followup on the Darex E-90