Kool Mist Misunderstanding?

For maximum pressure with perfect control when grinding, try Nathan's hanging parallelogram grinding arm. The blade holding fixture or magnet mounts on the swinging arm. In the photo, the blade is bolted to the arm through the tang holes.

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I'm obviously stupid. But what does the above pic show? And how does that correspond to heat build up from grinding?
 
It shows a system that gives maximum grinding force, as was being discussed. The hanging parallelogram method is a very good way to get maximum pressure buy maintain control. Your hands/fingers won't get burned because you aren't holding the blade. With one of these you can easily turn a blade bright red in hogging a bevel. Nathan could grind a perfect bevel in a few passes with one of these. IIRC, Salem Straub uses one with flood coolant for all his hogging.

BTW, don't get me wrong about a Kool-Mist system. It won't replace a flood system. However, most folks' shops are not setup for flood coolant and the resulting water to catch and control. Kool-Mist is easier to handle in a small shop.
 
I've seen steel boil and vaporize FLOOD coolant in extreme circumstances. I was not holding the steel. But to say that it will not happen is absurd.
 
Keith Nix said:
I've seen steel boil and vaporize FLOOD coolant in extreme circumstances. I was not holding the steel. But to say that it will not happen is absurd.
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I can melt steel on grinder if I want that .Yes ,it not happen to me to over heat blade and I don t use any coolant , absurd or not to everyone .
Thing is that everyone speak from own experience ,that is personal thing how you grind . I make more then enough knifes so I can speak about this .I never , ever overheat steel while I am grinding bevels .If I say that in a few occasions I can see some color on tip it will be lie. I guess most cases when they overheat the steel as when they grind second side , they forget that now steel have half thickness . From reading many topics here I can freely say that most have wrong approach to this job. And from there comes all the fame about overheating steel..............Learn to grind , read some books about grits , speed , pressure and other factor involved ! It may seem like a simple process but it's not ! After all we are not all the same ,someone gets that feeling / when the belt grinds steel properly / after a few knives someone never...........And jig , jig make life easier and has a million benefits over free hand grinding/overheating !
Last night I grind this small blade from T3 HSS hardened steel , single hollow grind on belt which I can bet that 99% of knife maker would thrown in the trash three years ago . Of course it took me a lot longer, cooling the steel after each pass, but I do it without single time to see any sign of over heat and colors on blade .It may sound like I'm praising myself , but guys, I've learned how to use a grinder !
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Justin W said:
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.
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No , I m not kidding at all .Obviously steel gets hot on YOUR grinder not in mine .You can speak only for your self and your way of grinding . If I use some kind of coolant steel will be on room temperature while i make one pass, maybe two !
Look , have at my disposal thermal camera which cost over 12000 $ , I have Thermal laser also ,which is very precise.So I make lot of test / which I didn’t have to do because my hand can feel pretty good temperature / and I know what is going on in MY SHOP , not in yours or in any other knife maker shop .
I just took this pictures , first is outside of mu shop , others are inside shop in different places , look that numbers , that thing MEASURE temperature damn good and is calibrated .
One more thing about me , everything I've ever read here and it seemed to me not quite right..........I do it my self to see/feel first hand .
In the spring I promise to record a video clip, from start to finish without interruption and editing and with thermal camera turned on all the time . To confirm what I am saying and maybe that to someone would help to see that there is way to grind steel very fast and without any overheat .
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Justin W said:
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
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I will quote you to make it more clear .I agree with everything you say .All I m trying to say is that there is SWEET SPOT between to much and to low pressure or speed where you can get max. cutting and less temp .build
 
FredyCro said:
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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As I mentioned, all it does is prevent the knife from moving downward, which necessarily implies that there is no angle control. It's essentially freehand grinding. Here's a time lapse in which I use the stick https://www.instagram.com/p/CRrD3d1nxtP/

However, angle control could be implemented in the concept. See my previous vid/device here
 
I have one suggestion for you who have problem with over heating steel .I think that you will easy understand what is going on .Take small angle grinder / 10-13000 RPM/ buy several cutting disk , I use 1x125mm. for cutting inox/stainless .First , do you know what is the difference between ordinary cutting disk and one for stainless ? Only in numbers of grain on given square surface on cutting disk .Why ?
Take several piece of steel , thickest you have .Hardened and not hardened steel.Start test with very , very low pressure and watch what is happening .At first it will cut nice , then it will start to create a lot of HEAT on steel and cutting will slow down drastically .What happened ? You simple glazed cutting disk !You not cut steel you tear? steel . Try that on hard and soft steel because there is huge difference which you will notice .You will glaze disk much faster on soft steel !
Take new cutting disk and try same with max / but safe/ pressure you can do it and cut .You will notice more heat on steel and cutting disk will wear extremely fast .Why ?
If you make enough test you should FIND sweet spot where you will have maximum cutting speed , less heat and disk will last for long , long time ! All this is relevant to belt grinders and you understand that , right ?
PS. There are grinding belts for use with less pressure for grinding steel .What is difference between them and belts intended for heavy pressure ?
 
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I think I will have to decrease my pressure. I was trying to keep the grinds more consistent by not having to remove the blade from the belt so often, trying to make the belts usable for more blades, and save my finger tips from burning.
Justin W said:
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
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That’s pretty interesting. I see these YouTube makers say, “make sure you keep your knife cool or you will ruin the heat treat” and then spend 12 minutes grinding between dips in water. I am so worried about messing up temper that at first sign of heat I will dip the blade. I guess I don’t need to be quite as militant about that.

Thanks for the replies and advice. I think I will try my mister system a few more times before considering it useless.
 
I still dip a lot, often every pass and sometimes leave the steel in the bucket a while and switch to another piece. It depends a bit on stock thickness. 0.06", you can do the first side a little longer between dunks, but when you get close to full finished bevels, you need to dunk a lot. With 0.11" stock, you can grind longer between dunks, and it is easier to maintain low temps.

Another advantage of frequent dunking is less thermal stress warping. I like to grind the steel with water on the surface and you can visually see the water vaporize off the back surface. This helps keep temperature under control too and gives a visual indicator of when you are starting to get hot. I also use an aluminum jig, which gives a little extra heat sink.
 
Regardless of what some folks say, the laws of physics apply in everyone's shop. While there are best practices in any trade, no one person holds the magic that can hold off the laws of thermodynamics. If you're experiencing a general heating of your blade as you grind it, you can be sure there was a much higher localized heat. Dip and be safe.

My experience with Kool Mist is that more air and less water provides more cooling. But I freely admit that is only my opinion.
 
P.Brewster said:
As I mentioned, all it does is prevent the knife from moving downward, which necessarily implies that there is no angle control. It's essentially freehand grinding. Here's a time lapse in which I use the stick https://www.instagram.com/p/CRrD3d1nxtP/

However, angle control could be implemented in the concept. See my previous vid/device here
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I have that video on my short list of jigs for a long time, didn't knew it was you. Thanks for posting it!
Since I saw it I thought about combining it with the Moen fixture for the ultimate jig...!

Pablo

 
Dominick Maone said:
I think I will have to decrease my pressure. I was trying to keep the grinds more consistent by not having to remove the blade from the belt so often, trying to make the belts usable for more blades, and save my finger tips from burning.

That’s pretty interesting. I see these YouTube makers say, “make sure you keep your knife cool or you will ruin the heat treat” and then spend 12 minutes grinding between dips in water. I am so worried about messing up temper that at first sign of heat I will dip the blade. I guess I don’t need to be quite as militant about that.

Thanks for the replies and advice. I think I will try my mister system a few more times before considering it useless.
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So I have noticed this as well. I'll tell you what though, even with a brand new 60 grit belt if I go 3 passes I'll ruin a temper. I grind one pass and then dip. I genuinely don't know how they do it, b/c if you pay attention too, they are always throwing lots of sparks so you can tell they are running fast and with decent pressure.
 
Ill also add that I have just started using a kool mist system, I run plain water, 60 psi, and the water valve is just about wide open. I didn't like the "mist" and go more for lots of water. It's a mess but it does indeed keep work cooler.
 
Skiller1nc said:
So I have noticed this as well. I'll tell you what though, even with a brand new 60 grit belt if I go 3 passes I'll ruin a temper. I grind one pass and then dip. I genuinely don't know how they do it, b/c if you pay attention too, they are always throwing lots of sparks so you can tell they are running fast and with decent pressure.
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I like sparks
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one ! 32 m/s
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done!
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One thing to add to the thread, for us, the ones that work post hardening, jigs need to be small or easily detachable so the blade can be cooled properly. Most jigs are to big for most buckets. A cool mist on a thin blade is not fast enough methinks.

Pablo
 
1.5mm thick 64 HRC 1.2519 steel , hollow grind to sharp edge.This time on new 40 grit belt , no cooling while grinding .Blank is glued with CA to that square stainless tube
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Finish on knife is from that new 40 grit belt
 
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