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
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"Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> wrote in message
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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
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Thanks! I will.
Lloyd
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Maybe "were"... not now. A few bucks more, now.
But I'm sure I can learn from him, even at that.
LLoyd
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"Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> wrote in message

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
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Thanks, Jim. The trig I can do, but that goes in the archive, because it saves me a LOT of math. <G>
Lloyd
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"Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> wrote in message

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
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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
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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.
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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.
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According to Darex, 0.010" below center.
Lloyd
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"Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> wrote in message

Perhaps--my maing point being that once it's been set, basically you don't fiddle with it.
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On Fri, 11 May 2012 12:15:50 -0500, "Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> wrote:>I've been learning on the Darex E90.

What size grit and what letter of hardness do they use in their aluminum oxide wheels?
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snipped-for-privacy@ptd.net fired this volley in

Not a clue, yet. I haven't investigated it. I will, of course.
Lloyd
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On Sun, 13 May 2012 16:22:03 -0500, "Lloyd E. Sponenburgh"

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.
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snipped-for-privacy@ptd.net fired this volley in

The general consensus is that the E90 is not designed to gash the ends, but I am pursuing references right now that it is not only possible, but easy.
If I figure it out, I will post it, and supply the reference info.
I do know the E90 does a really sweet job on both the flutes and the ends of a regular HSS milling cutter with the stone I got with it.
I'm just guessing, but I figure the Al2O3 wheel on it is about 80-grit. It's NOT a fine wheel. It's the "fine touch" (which I'm also working on) that does the job.
If you refer to other finish-grinding operations, one thing becomes clear: It's not so much the grit, but the feed, and depth of cut, and lubrication that makes for a smooth surface.
(which brings up another point about the E90; it's a dry-cut machine, which, with some fiddling, might also be altered, if it's necessary.)
LLoyd
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