Burning Edges?

[lonestar1979]

I do all my rough grinding and reprofiling on belt sander...and for more expensive knives i put them to stone after belt sander.Kitchen cutlery and cheap knives i just sharpen on belt sander,go slowly and with light pressure,ruined couple cheap knives before,but now dont have any problems.More expensive knives i dip in water to cool them down.Practice is key...and shouldnt have any problems .

 

[HyperXHyperX]

https://knifesteelnerds.com/2019/04/08/does-sharpening-with-a-grinder-ruin-your-edge/

Thank you very much. If I see correctly, the complete bevel is damaged all the way up. However, this is with more speed than the work sharp can put out. So it's kinda bad, but also not the end of the world bad what I did.

Without knowing what steel you’re using it’s hard to know what impact you might see with edge retention. (...) I have one user knife I made that got there in a spot while I was finishing it and I can’t tell any difference in performance during normal/reasonable use. (...) I quit using my worksharp because it always seemed to want to put a recurve in the knives I used it on.

Well, basically any steel. Ranging from 420 over D2 and S30v all the way to Maxamet or some spring steel. I also don't notice a significant performance drop in a knife that has a golden spot. The recurve is when you go back and forth without altering passing speed, you're basically sharpening double the amount in the middle of the edge compared to the tip/butt.

I think sharpening with a dry belt is inevitably going to cost you a little bit of edge retention, but if you're careful I think it's probably not significant.

Steps you can take to minimize overheating:
1. Slow speed belt. I recommend always using the slowest speed on the WS;

5. Treat your belts. Wood Turners Wonders sells a lubricant called Slick-Stick that's used to treat grinding wheels, belts and saw blades. I use it and it makes a noticeable difference.

I think that just annihilates the reason for using the blade grinder all together, which is speed. I'll look into some equivalent for the EU market. The next time I'll sharpen, I'll use ballistol and see if that helps.

It may also depend on what you are using the knife for. If you are cutting rope, a prudently used belt grinder may be OK. If you are opening cans, maybe not.

Does Sharpening with a Grinder Ruin Your Edge?

Stacy, how about providing some information on your mist system. It sounds like a good thing to have.

www.bladeforums.com

A lot of knives just cut cardboard, most are for EDC, but some are for cutting wood and a few for cutting people.

 

[ferider]

I'm not a chemist or knifemaker, but I can read data.

When your edge turns yellow, its surface was probably around 450F or so. The Apex of the edge was hotter.

Depending on the steel, and how long you keep it at that temperature, you might affect tempering. Google the tempering curve for a specific steel you might be interested in. Magnacut, for instance, per Crucible, requires "Double temper at 300-450°F (150-230°C)".

How much you affect tempering depends on the steel and how the knife was made. But - for a knife with optimized heat-treat - you can expect loosing at least a couple of points in hardness. Of course it will still cut when sharpened, but not as long. Now, again, depending on the steel, you might have increased toughness - good for you .

This is how you belt-grind optimized/expensive steel. These days, I try to stay away from makers that don't do similar (Photo/Equipment from Josh/REK):

Sharpening is a chore for me. But, I look at it much like at dish-washing after cooking - it has to be done properly. Unless it's a cheap kitchen knife, I use a wet stone. Otherwise, what's the point of this hobby ?

 

[me2]

I stopped using a belt grinder to sharpen a while ago. I had rippled edges on my 1055 steel choppers and a chefs blade. I never really noticed on smaller blades.

 

[Father & Son Traditional Sharpening]

One knife has a slight yellow spot at the upper part of the convex edge. I've heard it doesn't need discoloration to be ruined.


Well if it's mostly a surface thing, them I'm not worried.

You should've seen what I did to my ZT 223. I've never seen this blade shape anywhere; imagine grinding the last portion of the recurve flat, so it's like handle -> flat -> recurve -> tip


I've heard it can also happen without discoloring.

Yes, indeed. You can still blow the temper at the APEX in a matter of perhaps a fraction of a second because of how small of a mass we are talking about at this thickness of steel. It doesn't matter if the entire knife is cool the touch, this happens instantly at the apex where it can go well over 1000F. Best solution, grinding everything with coolant.

Is it cheap? Nope. Easier? Maybe. Worth it? Yes, I believe it is in indeed once you get over the price of admission. Many will not do enough grinding to warrant the price tag but if you sharpen a lot of stuff it's great.... wish I bought one sooner. The way I figure it many of us could do with less knives and more money tied up in high end sharpening gear

Here's my Tormek T8 when it was newer, I've actually just picked up a couple extra wheels from across the pond.... King Deluxe 800 & King Deluxe 4000. Did not even know these existed when I bought my Tormek and was pleasantly surprised that you can get these. The 800 makes a great starting point on dull knives, the standard SG-250 wheel is best suited to reprofiling.

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