Kool Mist Misunderstanding?

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I thought I had an epiphany the other day regarding wet grinding. Why can’t I just get a garden mister and use it with my hose?

Getting a kool mist or a knock off is a little cumbersome because I will need to get a decent compressor also.

So, I purchased the mister in the photos for 3.50 (clearance at Lowe’s). The mister itself works great, but not for this application. Even with my hose on full blast, with water dripping down the belt, the blade bevel was still getting hot to the touch after a few seconds with fairly heavy pressure. It was a slightly used 36 VSM. So, to be sure, I put a brand new blaze 40 and same thing. I don’t see how a kool mist can be better.

Am I misunderstanding what a Kool Mist system does? I was under the impression I could go from having the 45s cut into the bevel to zero behind the edge with a worn belt without removing the blade more than was needed to check progress. I even set up my ladder to make sure the mister was above where I was grinding thinking the water was not getting to the side touching the belt. If the videos work you can see how much water it is. Much more than the drop or two every few seconds that I have read recommended here as enough to keep the blade cool.
 
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Yes, you are misunderstanding the principal. The mist in a Kool-mist system is COLD. It also is a much finer mist that a wet-spray mist. The water is atomized, and the sudden pressure drop chills it a lot. The spray lubricant used is also very important. It makes the process much better than plain water.

Your wet-spray grinding system is fine for that type grinding. In pre-HT grinding, the temperature of the blade doesn't matter. As long as you can hold it, it is good. The spray does more to help the belt than the blade. On negative is it will toss a ton of water around the grinder and in the shop air.

In post-HT grinding, the blade needs to be kept below 350-400°F. That is pretty hot to the touch, so you have plenty of warning it is getting too hao. The cold and fine mist from an atomized pressure system cools the blade and lubricates the belt. It also uses out a fraction of the water that your wet system sprays.
 
My experience with a cool mist system is that it only gets really cold when the ambient humidity is low. If that's the case, you can use a very light mist and it keeps the blade pretty cool, but I don't know about using a worn belt and all that. If the humidity is high, I find I'm better off using a lot of water instead of a fine mist. The downside is it makes a huge mess and it's harder to see what your doing.

FWIW, the relative humidity in Baton Rouge is currently around 80%, probably too high to gain any significant cooling from evaporation.
 
You can play with the air pressure as well as the water flow rate to control the temperature. Use a cheap $10 pressure regulator at the grinder.
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So, I purchased the mister in the photos for 3.50 (clearance at Lowe’s). The mister itself works great, but not for this application. Even with my hose on full blast, with water dripping down the belt, the blade bevel was still getting hot to the touch after a few seconds with fairly heavy pressure. It was a slightly used 36 VSM. So, to be sure, I put a brand new blaze 40 and same thing. I don’t see how a kool mist can be better.
You are doing something wrong . It is impossible steel to get that hot after few seconds .
Instead of a video with water, take a short video while you grinding. This will help us to see how you grind and where you are wrong.What belts speed you use ?
 
What speed and pressure are you using?
 
Yes, you are misunderstanding the principal. The mist in a Kool-mist system is COLD. It also is a much finer mist that a wet-spray mist. The water is atomized, and the sudden pressure drop chills it a lot. The spray lubricant used is also very important. It makes the process much better than plain water.

Your wet-spray grinding system is fine for that type grinding. In pre-HT grinding, the temperature of the blade doesn't matter. As long as you can hold it, it is good. The spray does more to help the belt than the blade. On negative is it will toss a ton of water around the grinder and in the shop air.

In post-HT grinding, the blade needs to be kept below 350-400°F. That is pretty hot to the touch, so you have plenty of warning it is getting too hao. The cold and fine mist from an atomized pressure system cools the blade and lubricates the belt. It also uses out a fraction of the water that your wet system sprays.
I do all bevel grinding after heat treating. I guess part of my misunderstanding was that I have seen it said on this forum several times that dripping water on the belt is enough to keep the grinding cool. I have no way of distinguishing 150 degrees from 349 degrees, so I dip at the first sign of heat.
My experience with a cool mist system is that it only gets really cold when the ambient humidity is low. If that's the case, you can use a very light mist and it keeps the blade pretty cool, but I don't know about using a worn belt and all that. If the humidity is high, I find I'm better off using a lot of water instead of a fine mist. The downside is it makes a huge mess and it's harder to see what your doing.

FWIW, the relative humidity in Baton Rouge is currently around 80%, probably too high to gain any significant cooling from evaporation.
It’s 80%+ humidity here about 360 days a year.

I might be thinking the kool mist type things have a similar affect as flood coolant systems.
You are doing something wrong . It is impossible steel to get that hot after few seconds .
Instead of a video with water, take a short video while you grinding. This will help us to see how you grind and where you are wrong.What belts speed you use ?
I’ll try to take a video Tuesday. I grind 100% on vfd. 1.5 hp motor. Not sure what the belt speed is. It is 2x72.
What speed and pressure are you using?
Full speed, very heavy pressure. I don’t have a way to gauge it. Put probably as much pressure as to open a semi heavy door.
 
Full speed, very heavy pressure. I don’t have a way to gauge it. Put probably as much pressure as to open a semi heavy door.
That's your problem... The only way that will work and still keep blade cool is under flood coolant. That's how I grind 💪👍

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It’s 80%+ humidity here about 360 days a year.

I might be thinking the kool mist type things have a similar affect as flood coolant systems.
I think they work best by evaporating the tiny water droplets. When the humidity is low, the mist gets really cold, sometimes uncomfortably so. That's when the system works best for me, the blade stays cold and there is no mess to speak of. When the humidity is high, flood cooling works better for me, but it's messy.
 
You are correct - a Kool Mist system isn't better; those who claim otherwise simply aren't grinding as aggressively as you.

I grind with a crude support system that allows me to push the knife into the abrasive with two hands and one knee. I use flood coolant, and even with flood coolant, I absolutely can cook the steel to red-hot. Again, that's RED HOT while being sprayed with FLOOD coolant.
 
You are correct - a Kool Mist system isn't better; those who claim otherwise simply aren't grinding as aggressively as you.

I grind with a crude support system that allows me to push the knife into the abrasive with two hands and one knee. I use flood coolant, and even with flood coolant, I absolutely can cook the steel to red-hot. Again, that's RED HOT while being sprayed with FLOOD coolant.
That's interesting... I can rough grind (36 grit belt) a 5/8" high grind in cruwear or vanax (both hardened steel, @60-64hrc) on a 3-3.5" blade in a out 3-4 minutes under flood coolant as pictured above and the steel doesn't turn any colors, even at the tip. Shoot, even the dykem doesn't change colors from bright blue. My belt grinder is running at 4600 sfpm though and I'm using a decent amount of pressure since I'm using a jig.
 
That's interesting... I can rough grind (36 grit belt) a 5/8" high grind in cruwear or vanax (both hardened steel, @60-64hrc) on a 3-3.5" blade in a out 3-4 minutes under flood coolant as pictured above and the steel doesn't turn any colors, even at the tip. Shoot, even the dykem doesn't change colors from bright blue. My belt grinder is running at 4600 sfpm though and I'm using a decent amount of pressure since I'm using a jig.
Try using more knee??

Seriously though, I can't (and shouldn't, as it would be foolish to) dispute your personal experience, but if this is a mystery that you're seriously interested in unravelling, then send me a sample of your steel. I'll see if I can get it to discolor and I'll film a video. If I can, I imagine we'll conclude that I'm using less coolant than you, or I'm applying more pressure. I estimate that I'm doubling my in-feed pressure by using my knee.
 
Try using more knee??

Seriously though, I can't (and shouldn't, as it would be foolish to) dispute your personal experience, but if this is a mystery that you're seriously interested in unravelling, then send me a sample of your steel. I'll see if I can get it to discolor and I'll film a video. If I can, I imagine we'll conclude that I'm using less coolant than you, or I'm applying more pressure. I estimate that I'm doubling my in-feed pressure by using my knee.
No I'm not disputing that you can do it! I totally believe you. I am curious though - why do you need so much pressure, is it taking too long to grind otherwise? If you grind really wide blades I can see how you could need a lot more since the force is distributed across the grains - much more surface area. also what belts are you using? I've found some really build up heat more than others.
 
No I'm not disputing that you can do it! I totally believe you. I am curious though - why do you need so much pressure, is it taking too long to grind otherwise? If you grind really wide blades I can see how you could need a lot more since the force is distributed across the grains - much more surface area. also what belts are you using? I've found some really build up heat more than others.
I don't necessarily need that much pressure, it's that I attempt to minimize labor time whenever possible. I grind as fast/aggressive as my strength, precision and water spray allow.

I grind post HT (around 56 RC in the steels I use) with a 50 grit high-end ceramic belt (either Cubitron II, Norton Blaze, or Preferred Abrasives Firestorm II).
 
Something interesting happens at a few target temperatures.

120-140 °F (50-60 °C) steel will cause physical pain to your skin and possibly 1st degree burn/blister. This is a good thing because it is way below auto-tempering, though the edge could still be hotter than the area where your fingers contact the steel.

212°F (100°C) water starts to boil. This is below auto tempering, BUT water vapor is actually an insulator comparable to air. So, the steel can reach extreme temperatures depending on how much energy/power you are putting into it.

Mist takes advantage of evaporation, which requires a lot of energy, but can suffer from vapor barrier insulation since the mist does not have enough momentum to break through the mist and physically contact the steel.

Flooding takes advantage of more mass flow and to some degree has more momentum depending on how fast the water jet moves towards the steel. You can overcome the vapor barrier, but it makes a lot more mess.

If you overcome your cooling system, you have to put less energy/power into the blade. This means less pressure/force. The energy/power going into the steel is a byproduct of friction which is proportional to force. Too much force = too much heat
 
You are correct - a Kool Mist system isn't better; those who claim otherwise simply aren't grinding as aggressively as you.

I grind with a crude support system that allows me to push the knife into the abrasive with two hands and one knee. I use flood coolant, and even with flood coolant, I absolutely can cook the steel to red-hot. Again, that's RED HOT while being sprayed with FLOOD coolant.
That sounds interesting, would you mind sharing you fixture?
 
That sounds interesting, would you mind sharing you fixture?
It's literally a stick - a 40ish-inch long piece of wood with a notch in the top. The knife sits in the notch. The bottom of the stick rests on the floor. All it does is prevent the knife from moving downward. I push the knife with my hands and also push on the stick with one knee.
 
212°F (100°C) water starts to boil. This is below auto tempering, BUT water vapor is actually an insulator comparable to air. So, the steel can reach extreme temperatures depending on how much energy/power you are putting into it.

Mist takes advantage of evaporation, which requires a lot of energy, but can suffer from vapor barrier insulation since the mist does not have enough momentum to break through the mist and physically contact the steel.
Theoretically, you're right . You just forget one thing , steel is COLD when we start grinding and water cools it so that it does not reach the temperature at which the water evaporates.
 
Theoretically, you're right . You just forget one thing , steel is COLD when we start grinding and water cools it so that it does not reach the temperature at which the water evaporates.
You're kidding right? Nobody takes a chunk of steel hot enough to boil water on contact, in their bare hand, and then starts grinding on it. It gets hot on the grinder, and due to the properties of your skin and the delay of information to reach your brain and tell your hands to pull back, it can get extremely hot.

Ever heat a cast iron pan to screaming hot (not red hot, but hot enough to sear a steak), and then drip some water on it? The drops will bounce. Ever wonder why those drops bounce? Drops on a cold pan don't bounce. Flash boiling and steam vapor barrier is in fact a real and observable event, as anyone who does their own heat treating will attest. Steel doesn't need to be red hot for it to happen.
 
It's literally a stick - a 40ish-inch long piece of wood with a notch in the top. The knife sits in the notch. The bottom of the stick rests on the floor. All it does is prevent the knife from moving downward. I push the knife with my hands and also push on the stick with one knee.
Thanks, would still love a pic if you ever have a third hand around :) can't exactly imagine where the stick is on the knife and how you control the angle.
 
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