I'd like to chime in here.
I have never seen a diamond wheel (Baldor style grinder) run wet. (I run mine with drip/spray).
My experience with such grinders is limited to wet grinding only, aside from very recent happening. We had a Hammond where I was trained, and it was full flood. When I started my shop, I built one, keeping the design of the Hammond in mind. I provided flood coolant.
The recent happening of which I spoke is one where I have used my diamond wheel dry, for my shop is not in full operation. As a result, I haven't filled the coolant tank because the grinder is not in service. Fact is, the picture, below, is one taken where it sits in storage, obvious by the clutter that surrounds the grinder. I've used it only a couple times to put an edge on a fly cutter needed for a project in support of the house building project that has dominated my time. The difference between wet and dry grinding is like day and night. One of the biggest problems that has become more than apparent to me is the loading of the wheel. Run wet, they rarely load. I use a resinoid bonded wheel, which is the wheel of choice for tool bits.
My concern is flinging coolant all over everything, and perhaps coolant goo.
Most diamond wheels are recommended to be run wet, although I can appreciate your concern. My attitude is that if you intend to make an omelet, you must break a few eggs. My shop is intended to serve me and my needs. I can't allow the worries of a little spray to interfere with better performance. It is for that reason that I have run coolant in my lathe. Like in grinding, for me, it isn't a luxury, it's a requirement. YMMV.
I use a small pump, and deliver a constant stream of coolant to the center of the wheel. The discharge is a 3/16" copper tube, with a valve, so I can regulate the amount of coolant dispensed. Even roughing, a full stream isn't required. My wheel has a shroud, so nothing is thrown from the sides, although a small stream can deflect from the top of the tool being ground. A well placed finger deflects the stream back to the table. When grinding wet, rebuilding a chipped edge is nothing-----happens in seconds. Diamond wheels have propensity for moving hard substances quickly, as long as you can keep the wheel cool, and free of loading.
I've posted a picture of my diamond grinder, below, so you can see how I've made provisions for running coolant. A fine mist radiates from the grinder when in use, but there is no puddling on the floor. The coolant reservoir holds less than a gallon of coolant, so losses can't be tolerated. When I was actively machining, coolant losses were from evaporation, not dripping.
Harold, a mini tutorial about flood coolant for diamond wheels, or a link to a past post would be appreciated
Sadly, my experience with carbide grinding is limited to that which I have done on my own. I have had no formal training in the art---unlike cutter grinding of HSS. I have simply emulated that which I witnessed in the shop where I was trained. I don't know that I'd feel right in suggesting what others should do, but I can guarantee you one thing----if you follow what I've talked about here-----you won't be disappointed. I know what I do works, and works exceedingly well. So well, that I have never been concerned with making any improvements.
For the record, there's no way in hell I'd consider running a diamond wheel dry on carbide. It just 'ain't gonna happen'.
Also, if using flood coolant, is there still the prohibition on grinding HSS. (I'm not talking about hogging, just the final kiss.)
It's your wheel, so I'd be out of line telling you you shouldn't be doing any such thing, but if my logic appeals to you, it's like this: diamonds are carbon, which is readily absorbed by iron at high temperature. This isn't speculation. Norton did considerable research on the subject in the 50's, and it has been documented.
In spite of cooling, the temperature at the interface of the wheel and tool is great enough to cause diamond to be dissolved. Dressing a wheel at red heat does not harm a diamond----obvious when an 8" wide (or greater) wheel of a centerless grinder can be dressed with no problems, so there is obviously something going on that is out of the ordinary.
The harm isn't in the tool, but the loss of sharpness of the diamonds in the wheel. When the edge is gone, the diamond ceases to function properly, and performance is restored only by dressing the wheel. That shortens the life of diamond wheels considerably, for the surface of the wheel is eroded, exposing new diamond and liberating the old. It is for that reason that I suggested in my previous post that diamond wheels should be dressed sparingly.
You can conclude that if you slow down the wheel, all of that changes. If the surface speed is too low to create a red heat at the point of contact, diamond will do an admirable job on HSS tools. It is for that reason you see diamond lapping machines for toolbits. The wheel is slow speed, so the diamond isn't harmed.