sharpening?

^This. Any way you slice it, visible sparking indicates that material achieved temps somewhere north of 900F (incandescent color is correlated to temperature across materials). I can't accept spontaneous combustion upon exposure to oxygen as the best explanation here. If that were true, hand shaping/finishing would be quite a different experience!

There is solid evidence to indicate that it is the actual work of the swarf being ripped out of the parent material that generates the ignition temps. You can't escape either the frictional heat related to that work or that it is happening adjacent to what will become your customer's cutting edge. All you can do is manage it.

I am not saying belt grinders don't work well for sharpening in thoughtful hands, but there is little doubt that the risk of over-drawing your edges is virtually eliminated by hand sharpening.

Also I would question the effectiveness of any sharpening method where you attempt "Keep the edge off..." the media. Until you grind your bevel planes all the way out to the apex (or, more commonly, through it by forming a burr), you will never develop a high-quality edge. It may cut well enough for awhile due to being thin shouldered, but initial keenness and durability will both suffer. At best, you will have a ragged apex that is equivalent leaving behind a giant wire-edge burr. Maybe I am missing something here?
 
Spontaneous combustion upon exposure to oxygen, from my measly understanding, is EXACTLY what takes place when flint is struck on steel.
 
I've done it just on the grinder, just with a lanky system and both. I currently do a combination of the two. I use the grinder to start the bevel then when it gets close I switch over to my Lansky to finish and even everything out. When doing it using just the grinder I had issues with getting everything perfectly even and not screwing something up. Now I could easily get it shaving sharp using only the 2x72 or even my HF 1x30 that wasn't the issue. I started out sharpening my knives only on the grinder. I want it to be perfectly even and uniform and I have better success with that by using the Lansky for the final steps. I tried doing it all on the Lansky once and that took forever. Once done with the Lansky I use a leather strop with green compound.

If I had my grinder set up to run in reverse, with a flat platen that fit under the horizontal part of the belt between the tracking wheel and the top idler wheel and had some sort of angle jig set up then I would be golden and could do the entire process on that and get it just perfect.
 
phorizt said:
If I had my grinder set up to run in reverse, with a flat platen that fit under the horizontal part of the belt between the tracking wheel and the top idler wheel and had some sort of angle jig set up then I would be golden and could do the entire process on that and get it just perfect.
Click to expand...


Take a look at Ray Ennis set up


https://youtu.be/dgkkWz73Yro?t=1m40s
 
samuraistuart said:
Spontaneous combustion upon exposure to oxygen, from my measly understanding, is EXACTLY what takes place when flint is struck on steel.
Click to expand...

Not exactly. The term is generally applied to organic materials that ignite due to internal self-heating (e.g. exothermic chemical reactions in oily rags, damp hay, coal beds, etc.), rather than by energy being introduced from the outside as is the case for a flint striker (or a belt-driven ceramic particle) smashing through some carbon steel.

It takes energy to generate those spark showers. That energy is not coming from inside the steel, but from the friction/abrasion being applied to it. Right at the cutting edge. As it is being formed. All I am saying is, if that is your approach, the associated risk is worthy of serious attention.
 
Andy, I'm not going to say that deforming the metal doesn't produce heat that needs to be managed, of course it does- that's a very good thing to keep track of.
The phenomenon I described is real, as are the ones described above by our very knowledgeable Stezann.
Think about it: if the presence of sparks meant only that the edge was getting hot, would that mean that AEBL doesn't get hot? It doesn't spark much if at all, since there's no available carbon.
As he said, Hypefreeblades has some excellent discussions.
As far as I could see in reading all the posts, it hasn't been established that the fine edge loses enough hardness to matter from skilled sharpening, though water cooled sharpening has some strong advantages.
 
I use my 2x72(variable speed) running as slow as possible and use a jig system with my platen set for a certain angle(via digital angle finder). It's the same setup as this guy only my blade is clamped between two pieces of angle iron so I don't have to remove the blade to switch sides:

https://www.youtube.com/watch?v=eDHxENG9AAQ

It works very well and is very precise. Also, when you setup up your blade in the jig edge down, you don't have to worry about running the belt grinder in reverse. I continually dip the blade after each pass just to be safe. I've done tests and my edges hold up real well.
 
Gotta love Ken Schwartz' set up for sharpening knives!

Here, check it out:

[video=youtube;XSF3VF9aIp0]https://www.youtube.com/watch?v=XSF3VF9aIp0[/video]


Man I wish I knew enough about wiring to set up my grinder for variable speed :( lol

~Paul
My YT Channel Lsubslimed
 
I'm not a knife maker, but I've put in my dues sharpening knives. For me it all depends on the steel and application because geometry is so important. I've gone back and forth between convex and v bevel, but I'm currently preferring convex on all of my knives. I use a variety of stones, an Edge Pro, Lansky, 1x30, 3m paper and my own brand of strops and compounds.

This isn't in relation to sharpening, but those of you who don't hang out in Maintenance might not have seen this new instrument. It's the first accurate edge sharpness tester and uses media designed for the job. I have a test unit, but haven't been able to run it yet. The preliminary reports indicate that it is very accurate and I'm personally very excited to try it.

Check it out.

http://www.bladeforums.com/forums/showthread.php?t=1285538

Set up video. I can confirm that it is very well made.

[video]https://youtu.be/bNlLFkmG5yA[/video]
 
Omega Leather Works said:
I'm not a knife maker, but I've put in my dues sharpening knives. For me it all depends on the steel and application because geometry is so important. I've gone back and forth between convex and v bevel, but I'm currently preferring convex on all of my knives. I use a variety of stones, an Edge Pro, Lansky, 1x30, 3m paper and my own brand of strops and compounds.

This isn't in relation to sharpening, but those of you who don't hang out in Maintenance might not have seen this new instrument. It's the first accurate edge sharpness tester and uses media designed for the job. I have a test unit, but haven't been able to run it yet. The preliminary reports indicate that it is very accurate and I'm personally very excited to try it.

Check it out.

http://www.bladeforums.com/forums/showthread.php?t=1285538

Set up video. I can confirm that it is very well made.

[video]https://youtu.be/bNlLFkmG5yA[/video]
Click to expand...


The convex edges you produce on your knives; are they convex from start to finish, or are you producing an edge that is flat at the apex and rearward toward the spine, with the convex portion being across the shoulders, rounding this area to give less resistance while passing through the material being cut? I associate full convex with edges produced on a slack belt, as opposed to edges produced on a plate or stone where the result is more a combination of convex and V edge geometry.

Fred
 
Fred, it depends. On this knife it's what I consider a true convex.

IMAG0784_zpsd5ec980f.jpg


The blade was sharpened on a 1x30 then stopped.

Most of my blades that are "convex" are as you describe though. I'll create a v bevel, then round off the shoulders with paper over leather, or by creating facets by moving the arm on the edge pro.

My wood carving and leatherwork knives are maintained convex from the maker.

I love a zero grind, but only on the knives that I consider novelty edges.
 
Anthony,

I started rounding the shoulders on all my edges a few years back, they cut better in most situations. Machetes on a slack belt work well, or most any chopping tool. My kitchen knives are as close to zero grind as I can get them without foiling along the edge. With kitchen knives it allows for the production of a fairly obtuse angle on a blade thats used to slice thin. I like the way the cut feels. I "convex" these shoulders as well. Less drag.
Does it appear to you that there is a lot of positive learning in the knife community about edges over the past couple of years?

Thanks for the reply, Fred
 
Fred.Rowe said:
Does it appear to you that there is a lot of positive learning in the knife community about edges over the past couple of years?

Thanks for the reply, Fred
Click to expand...

Absolutely. As you know, one can get utterly lost in the M&T forum. Before I started working with leather I spent many hours reading, learning and practicing making and maintaining edges. I have an Opinel that has probably a dozen hours in modifying (thinning the blade by hand, shortening the blade into a 1.5" wharncliffe, bouncing around with grinds, etc.) That was just an exercise in trying to pass a hanging hair test, but I do believe 90% of us stand to gain a lot by taking cues from the pros and hobbyist alike.

For me, when I get a custom knife, the first thing I notice is the f&f. After that I notice how well it cuts the media it was designed for and it better be excellent.

The enthusiast customer is learning more every day about geometry. I don't mind applying my own final edge, but the rest I expect the maker to nail. Nothing worse than buying a custom kitchen knife and having it thick behind the edge. Sounds like you do yours just how I'd like it. ;)
 
Bill DeShivs said:
It puzzles me how knifemakers can't sharpen knives without jigs.
Click to expand...

Well, we can. Or I can anyways and that's what I do in the kitchen etc. for my own knives, but not the stuff I sell.

I liken it to a good marksman using a scope. Just because you have a talent doesn't mean it can't be improved with some instrumentation.

I think it depends a lot of the sort of knife a person is making. For me, personally, I like to make work that is fine tuned and repeatable. I'm a nerd. There's also nothing wrong with heat treating in a charcoal forge and eyeballing the temperatures by color, but I don't work that way, I'd go broke. If I find a particular steel and geometry and HT combination works well at 15 DPS but not 13 then I want to control that. Yeah, one could go for 20 DPS and be pretty safe, but that's not what I want to do.

Part of it is because I'm lazy. I don't have the time and energy to spend hours testing and tweaking and loving on every single knife. Once I have a HT and geometry figured out for a particular pattern I want it to repeat. I want to do the work one time and then I want the next one to be the same. And the next one after that and the next after that etc. I want to sharpen 20 knives in one afternoon and know for a fact that every single one of them is going to behave a certain way and controlling that angle is an important part of that.

It is also nice to be able to tell the customer specifically what angle their knife is at so they can duplicate it. Not what I think it's at. Not where it's at on one side or for a certain length, but what is the exact edge angle. For a lot of knife enthusiast that cut a lot of stuff, this is important. :thumbup:
 
Nathan the Machinist said:
Well, we can. Or I can anyways and that's what I do in the kitchen etc. for my own knives, but not the stuff I sell.

I liken it to a good marksman using a scope. Just because you have a talent doesn't mean it can't be improved with some instrumentation.

I think it depends a lot of the sort of knife a person is making. For me, personally, I like to make work that is fine tuned and repeatable. I'm a nerd. There's also nothing wrong with heat treating in a charcoal forge and eyeballing the temperatures by color, but I don't work that way, I'd go broke. If I find a particular steel and geometry and HT combination works well at 15 DPS but not 13 then I want to control that. Yeah, one could go for 20 DPS and be pretty safe, but that's not what I want to do.

Part of it is because I'm lazy. I don't have the time and energy to spend hours testing and tweaking and loving on every single knife. Once I have a HT and geometry figured out for a particular pattern I want it to repeat. I want to do the work one time and then I want the next one to be the same. And the next one after that and the next after that etc. I want to sharpen 20 knives in one afternoon and know for a fact that every single one of them is going to behave a certain way and controlling that angle is an important part of that.

It is also nice to be able to tell the customer specifically what angle their knife is at so they can duplicate it. Not what I think it's at. Not where it's at Youon one side or for a certain length, but what is the exact edge angle. For a lot of knife enthusiast that cut a lot of stuff, this is important. :thumbup:
Click to expand...

Its important to me also. You stated the issue well. When I deliver a knife to a customer I want to be able to tell them how to maintain the edge to the exact level of sharpness that it was make and delivered. I take pride in doing so.
I can sharpen on a rock if need be.


Fred
 
I'm going to stick my neck way out and say something very controversial here:

Not directed towards anyone in particular:

If you sharpen dry and claim it's just as good as sharpening wet but have never actually experimented with your process and truly validated your claim, what you have is an unsubstantiated opinion and you don't really know.

I have no problem with people sharpening dry. Most folks do it that way. I don't care, I have no dog in that fight. What bugs me is when people who sharpen dry say "I do it this way, it works fine, no customer has ever sent a knife back, there is no reason to sharpen wet it's just as good" when they don't actually really know.

Test it for yourself. It's extremely simple. Do these two simple things:

1: do a side by side test and prove it to yourself. You need two identical work pieces (same steel, same HT etc and same controlled edge angle) and do one wet and one dry, then cut identical amounts of the same materials and view the edge under bright light and magnification and see how well the dry ground edge holds up compared to the wet.

2: test to see how far out of whack your sharpening process needs to get to actually color an edge. A somewhat dull belt, a little too much pressure, move a little too slow. How bad do you need to screw up to clearly ruin an edge? You all know that most steels we work with will not run color after a brief trip to high temp unless you really burn it. So generally speaking if you can see it, you're probably way over the line. It's easy to do.

Most modern steels get pretty hot when you sharpen them because the alloy content slows heat conduction and high carbide steels take more effort to abrade. Couple that with the thinner edges of high performance custom knives and you have the real possibility of the occasional burnt spot without ever knowing it.

Again, I'm not saying there is anything wrong with folks sharpening dry. I think it's an acceptable way to do a reasonable job if you're careful. But for those same folks to claim there is no difference when they themselves have not actually tested it, and then disregard the claims of those who have, is not good.

I have tested it for myself and formed my own opinions based upon the materials and geometry I'm working with and what I consider "acceptable" and have opted for a wet setup for sharpening. It's not as messy as you might think.
 
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Nathan, I assume you are talking about wet versus dry belt grinding?

In any case, I'm gonna need you to send me a couple of blades so that I can confirm or deny your findings. :D

Btw, huge congrats on your work with Andy. I really hope to sample these against the handmade knives, but I expect great things. The reviews have been overwhelmingly positive, and I know that neither of you would allow them out the door without their being excellent.
 
Nathan.....thumbs up. What gets me more than anything is when guys who sharpen dry with the belt say, "So and So company just released a video and they show their sharpening process before sending knives out and they grind dry on the belt/wheel.....so if they do it, it must be right."

And then you hear the threads where, "my new knife from so and so company did not keep it's edge until I sharpened it by hand a few times on the stone....why?"
 
Like most processes in the shop there are good ways to approach them and ones that are not so good. I have both a wet and dry belt system in my shop and I use both to sharpen knives. If putting an initial edge on a blade and using a dry belt, several things are necessary, first, only use top quality "new" belts. I use Trizact CF belts for dry belt sharpening. Use a slow sfm belt speed with little pressure. New quality belts with very light contact makes for very little heat build up. I sharpen with a BJ so the angle of approach is always correct. Using the above technique will produce a sharp edge in only a few passes. I always follow the belt machine sharpening with finish work on a diamond plate or an ERU set with a matching angle.
My wet set up is on an old Pro-Cut 2 X 72 VS machine. This machine is reversible so the spray can be kept at a minimum. With the wet machine I use 3M Regalite polycut belts. Some of the same techniques are used such as light pressure, using known angles of approach and don't let the blade stay stationary. Keep moving. This is one good reason to use a system that maintains the angle of approach. There is no hesitation when the angle is known.
I finish all tips on the diamond plate; the tip is the easiest place along the edge to overheat.

We make many blades with thin stock which in most cases means, grinding after heat treat. Much of the above technique applies to this type of grinding as well.

As in most shop work it takes practice to do it well. Working with someone that has experience in the particular skill or technique you are trying to learn is a real confidence builder. Most makers are willing to share what they know.

By the way, Nathan's comments above are dead on. I do think its important to encourage people to critic how they work and to be able to adjust one's technique as skill is acquired.

Fred
 
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