Extending diamond dresser life - proper use.
David Barnett - Venice, FL
>Ah, William. I just saw your post on mounting single point diamond dressers (last week), and now you've gone on vacation, but maybe you have internet access. Anyway, in the interest of succinct pedagogy (yeah, right), I'll be blunt (although not as blunt as your diamond point is going to be if you don't heed my advice, heh). While I don't want you to abruptly flatten your new diamond tool, most of what I have to say concerns safety, and while much is intuitive, some is not. So here goes* (in no particular order):
Single point diamond dressers should never address the wheel into the direction of rotation.
They should always address the wheel at exactly the centerline (horizontal radius) or 1/32" below the centerline.
Nextly, angle the tool 10 to 15 degrees downward, that is, the exact point of the diamond should be the last thing to drag against the rotating wheel.
Penetration should be only .001". No kidding. On highly friable white wheels you can get away with twice that - about half the thickness of a dollar bill.
Never increase penetration while the wheel is running. This can catastrophically split the wheel. With the Veritas tool rest and jig, be careful not to lower it into the wheel. The jig is designed to do so which is fine for grinding blades but dangerous when used with a diamond dresser unless one has carefully set maximum penetration depth to compensate for this motion. This is NOT a design flaw in the Veritas jig, so don't blame it on LV. Best is to make a jig (like William's) to ride in the groove of the Veritas tool rest.
The diamond tool must be held rigid at all times. Chatter or vibration can destroy the diamond, disrupt the wheel surface or shatter the wheel.
Traversing feed rate should be about 16" to 28" per minute, so count to 4 (or 2 if you're really impatient) as you complete one pass on a 1" wheel.
You should rotate the tool to maintain point symmetry. This cannot be done safely by rolling the tool whilst traversing as the tool should be clamped fast. So rotate the tool frequently between passes.
Never start a pass with the point off the edge of the wheel. Not only can this shatter the diamond but also the wheel.
Always start each pass with the diamond on the highest point; that is, at the point of greatest diameter. You can find and mark this with a soft pencil or Sharpie while rotating by hand.
Wear away high areas first in passes of .001 to .002".
On final passes, overlap from center to outside one direction, then the other, with penetration at .0005", ideally. This should give you a good surface for most tools. To get an even finer surface, make two more passes without increasing penetration. If you press ever so slightly on your jig for two passes, then let off completely for two passes you'll produce an incredibly even and flat surface. Don't try this if your toolrest or jig is not rock solid, though. Do a dry run on every operation and abandon any operation of which you are unsure or that leaves you uncomfortable.
Final passes, the traversing feed rate should be from 6" to 12" per minute, so count to 5 or 10, depending on how patient you are.
Use a piece of maple or hard rubber to remove stray grinding crystals from wheel before proceeding.
Ideally, the point should be flooded with coolant, but this isn't gonna happen so you and I will just ignore this.
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Okay... let me briefly mention that there are differences is single point diamond dressers. The best of these have a complete octahedronal diamond crystal set in the end. When one point wears down, these can be reset to a fresh point (6 sets max., 4 avg.). I do this myself, of course, but I'm a stone setter, so you'd have to send yours back for resetting if you go this route. As that'd cost about 8 or 9 dollars each reset, you have to decide whether this would be worth it on your next tool. I'm thinking that commercial interests are more likely to realize economies of reuse than casual users, but I thought I'd mention it as there are toolmakers here. As you can get a .5-carat diamond tool for $7.95 from Enco, or a 1-carat for $14.95 ($9.95 on sale), I'd opt for the disposables.
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A couple things I do: I elevate my Veritas tool rests to near the radial axis (centerline) with spacker blocks when mounting them to use the least extension of the locking arms. This maintains better rigidity (less flexing). My jig uses a screw to set the penetration depth of the dresser point. A micrometer screw does this nicely but even a regular fine thread machine screw works fine in a tapped jig. Dial indicators or even shims can give a good idea how much to turn an unmarked screw.
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Anyway, just keep resurfacing until you get 7" diameter wheels, which is a perfect place to start, IMO.
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*I can't begin to recall where I picked up all this, so I can't give proper attribution, but in the interest of safety I thought I should post it. I'll try to find sources if anyone needs to know.