Grinding Post HT and kool mist system

weo said:
Good morning, Cush. Do you have a VFD on your grinder?
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I do, and I was running at a slower speed with a 120grit belt. A couple things contributed to this ... I was grinding vertically .... and I am definitely still learning the ropes on that technique. The other is that I was specifically working to eliminate coarser grit lines in one specific location near an edge (which was already pretty thin), and put just a ***little*** too much pressure there. Honestly, I’m not even sure if a cool mist would have prevented that particular burn ... but it is worth a try. I also suspect I am talking myself into a ceramic platen...
 
12345678910 said:
Is it his machine frame that's rusted, or is it just the dust that's caked up and rusting.
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It looked like it was the entire machine from the videos, and I think he even has talked about it a little bit.
 
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I'm confused, I thought this was about TW90s rusting?
razor-edge-knives said:
Def. The machine, was pitted pretty deep.. These are the only 2 pics I have but the belt side was way worse.

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i-cL4RSds-X4.jpg


And here it is after the rework :)

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Cushing H. said:
I do, and I was running at a slower speed with a 120grit belt. A couple things contributed to this ... I was grinding vertically .... and I am definitely still learning the ropes on that technique. The other is that I was specifically working to eliminate coarser grit lines in one specific location near an edge (which was already pretty thin), and put just a ***little*** too much pressure there. Honestly, I’m not even sure if a cool mist would have prevented that particular burn ... but it is worth a try. I also suspect I am talking myself into a ceramic platen...
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Do you grind with gloves or bare handed? I do it bare handed and I use my thumb for pressure on the blade where the grinding is happening. If things start to heat up I feel it fast. Have burnt one tip so far (i've only ground about 30 blades total) and everything else got off fast because my thumb got hot. Most of those hot finger moments were trying to stay longer on a location like you describe here.

Ceramic platen is really easy to do Cush. I ordered three pieces of glass a year ago...paid about 12$/piece I think. Bit of JB weld and it has held well. One thing to make sure is that you don't get the glue up near the edge of the glass where the belt will be able to touch it. It melts the glue eventually and moves it down onto the platen creating lumps that you have to scrape off. Of course the lumps cause all sorts of problems as you grind because your platen isnt flat and you don't realize it. Took me five times of scraping epoxy off the face of the platen before I got out my dremel and fixed the issue.
 
I’ll remember that bit about the glue Randy - thanks.

I grind freehand and bare handed. Agreed, the “ouch” factor usually protects the steel :-) .

Where I have Had issues with burning Has usually been at the tip where it is easy to “torque” the tip harder against the belt (I have learned to be careful to really watch how much time the Tip spends against the belt). Grinding vertically that issue seems worse because it is really hard to avoid having the tip contact the belt! However, tip burns have so far been pretty easy to deal with by doing a little judicious re-profiling...

This last case was a little unusual, as I had just this little spot about 2/3 of the way back on the edge where old grind marks were not coming out (Btw, knife in question is an oversized Nakiri ). ... so, I decided to add just a “little” more pressure right there with a dowel. Stupid, stupid, stupid. It quickly went “poof”, and created a thin/burned area MUCH bigger than the original remaining grind marks (I should have just left the darned marks). I was able to reduce the size of the spot By some significant upward sweep at the heel of the blade reaching almost halfway up the edge towards the tip ... But unless I do something really drastic (like grind back the entire Edge 1/4 inch and re-grind the bevel) it will forever have a small soft and discolored spot... it is going to a friend as a gift, who I know will not complain ... 95% of the edge is just fine, but I will make clear to him that if it develops a divot or chip I will re-profile and fix it...

just a couple asides ... I’ve run in to this when I bring the edge down to something like 0.005”. M halfway tempted to stop at 0.01” ... but you get such a GOOD cutting edge with smaller TBE, I continue to chase it. Also, Stacy keeps saying he gets his edges down to almost zero, so there has to be a way to accomplish it :-). I also suspect that part of the issue is what is being said in a currently parallel thread - fresh belts cut cleaner and COOLER!
 
Randy - BTW - as you are in transition at your parents and then in your trailer while you build ... are you going to be able to connect and still participate in the forum?
 
It's not only that these mist systems keep blades cool while grinding, it's the results of the grinding. When I installed a mist system on one of my grinders five years ago I started turning out thinner and better blades. No more risking those thin grinds "before" heat treat, resulting in a crinkled edge. All knife shops should have a way of grinding after heat treat. It makes you a better knife maker. It did me. Fred
 
So .... just in case someone else goes with this inexpensive spray system..... The one I ordered was delivered. Seems basically ok, BUT to make it work you will need to attach a magnet to the side to mount it to your frame

  • $18 for 4 1" square neodymium magnets at my local hobby store,
And you will need to create the air supply/pneumatic hose to feed it from your compressor. Grainger has the parts, but after looking around, it is just as timely and less expensive to go ahead and get the pneumatic hose/connector kit that Amazon advertises as "commonly bought with" the sprayer ($17)

https://smile.amazon.com/gp/product/B07RM5WWBT/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

so ... to make this thing work, you will need to add on something like $35-40 to the cost to make this thing functional

(I am a little concerned that the liquid feed hose is not really long enough to reach down to the floor .... but I guess you could put the liquid supply jug right on the grinding table - that would help the liquid flow anyway.....)
 
I bought a cheap $9 setup off amazon a few weeks ago and just screwed it to the side of the plate holding my flat platen. I removed the push-lock air fitting and just attached a normal air line quick disconnect so I could plug it straight into my compressor. I've found that to work really well. The only problem I have with it is that it requires much more air to draw the water through than I'd like. I don't need a high volume of air, just a fine mist and some air flow. In adjusting the air flow, there's a rather sharp break point where it goes from a lot of air pulling a reasonable amount of water to not pulling any water at all. I haven't figured out how to modify the system to get it to draw water more efficiently yet.

I'm just drawing water out of a 2L bottle stashed under the table my grinder is mounted on. I can grind a full 210mm gyuto without needing to refill it. The bottom of the bottle is only about 2' below the outlet of the sprayer so it doesn't need to fight gravity too badly.
 
Cushing H. said:
Randy - BTW - as you are in transition at your parents and then in your trailer while you build ... are you going to be able to connect and still participate in the forum?
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I still will hang around and learn for sure. Maybe I should negotiate becoming the Canadian franchisee of Greenberg woods and start selling wood while I wait to get the new place done. :D:D
I was just going to screw the misting unit to the side of my grinder too replace push fitting too. Now I'm interested if the different sizes of hose make any difference on how the sprayer functions.
 
Try placing the bottle of water above the grinder. The gravity feed (once primed) will make the air aspirator need less pressure.
 
It would just be a little cumbersome for me to permanently attach the thing to the arm ... so magnets it is for now. And .... with the magnet I would worry about the weight of a full up air chuck :-( . For a compressor I have an unused airbrush compressor which I strongly suspect won’t work .. but heck, this thing works on exactly the same principle... so who knows?
 
So ... as luck would have it .... Harbor Freight just pushed out a coupon for a 1/3HP 100psi compressor. Looks like it is rated at 1cfm at 40 psi (dont know what it is at 20 psi, but maybe 1.5cfm or so...??

I am having trouble finding a definite answer on what kind of air supply is needed for the the KoolMist systems. does anyone know if this compressor would work?
 
30 to 125PSI is the spec range. I think most folks run them around 80-100PSI. Most any small pancake compressor will work.
 
I run my dual mister at about 28psi, higher and I get a fog all over the shop.

Cush, I'm not sure of the rating but I think it would work fine, it doesn't use much air.
 
Thanks - it’s a good price, so I’ll try it. It’s either that or I sacrifice my high pressure compressor from my RV, and I’d rather not do that ... really bad juju if a tire runs low and I don’t have the compressor!
 
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