Belt Sander VS Edge Temper

[A. G. Russell]

I do not have a dog in this fight BUT while Jerry is much younger than I, perhaps like me he sometimes confuses convex and concave. all the best, A. G.

 

[Jerry Hossom]

A.G., I don't think I said convex edged chisels were commercially available. This was a study done by some people who were evaluating steels used in woodworking tools. They tried convexing some edges (at my suggestion) as an anecdotal part of that study. Actually I'm really not sure that "edge" is the proper term for the bevel at the front of a chisel. It was the bevel they convexed and I really don't know how much of that bevel and on what kind of chisel was convexed.

I used those links so the gentleman who commented above could point out which of those chisels were hollow ground.

As for who's older or younger, I'm 66 so I doubt there is a whole lot of difference in our ages. I am prettier than you though. I am however old enough to know the difference between the concave (hollow) grinds and the convex edges I use on my knives.

I don't have a dog in this hunt either. I was simply trying to share some of my experience. That frequently leads to some difficulties on these forums. I should know better.

 

[Cliff Stamp]

It was the bevel they convexed and I really don't know how much of that bevel and on what kind of chisel was convexed.

That would be the problem, this is exactly what leads to the most common source of misinformation on convex edges. If you take a chisel which is sharpened at say 25 degrees and is microchipping and you increase the very edge to 30 degrees and then cut the upper bevel back to 15 then you note a large increase in edge retention and cutting ability. If you do this with a convex grind you may then incorrectly assume, as is common, that it is the convex curvature which is increasing the performance.

Trivially you could for example apply a convex grind which just increases the edge bevel and applies no relief so the cutting ability and edge retention will decrease. Does this mean convex grinds degrade cutting ability and edge retention. It certainly does using the previous logic. You could also apply a convex bevel which undercuts the entire bevel and thus the edge retention degrades almost instantly because the bevel collapses and there is no cutting ability.

Most of these problems would not exist if more people described the geometry of said convex bevels being exact about the angles and the thickness.

-Cliff

 

[Dog of War]

Good Japanese wood chisels usually have hollow backs, you can see that on some pictures on the Lee Valley site. I know that some, like Iyoroi, also hollow the top bevel on their thicker chisels, my understanding is that this is done mostly so that they're easier to sharpen. I also know it's popular with a lot of wood workers to grind the top bevel hollow, I assume for the same reason.

Honestly I wish you had more detail on that testing, Jerry. Pretty much all I know about this is what I learned from my grandfather and uncle who are custom furniture makers. To them a convex edge was what you got if you did a sloppy job of sharpening a tool by hand so they dismissed it outright. I respect their skill and knowledge, but also know that even the best craftsmen sometimes do things the traditional way without really knowing why, or even if it's the best way.

 

[Jerry Hossom]

Cliff, when you begin posting photographic or some other form of hard evidence instead of "here's what I've seen or measured or think", I will be willing to accept some of your premises and conclusions. Until then they are as indeterminant as you accuse mine of being, though I will admit you use a lot more words in expressing your thoughts than I do.

Dog, I also wish I had more to offer on those chisel details, but frankly it was outside of my knowledge base or focus at the time so I didn't delve into specifics. I was simply advising them on steel qualities. I do recall the comment that hand honing (no guide) on a stone over a long period of time would inevitably result in a convex edge because it is physically impossible to hold an exact angle time after time after time. In many cases the simple motion of the edge moving forward on the stone as you push it would cause the top of the bevel to increase in angle, making it convex. I don't think this is hard to imagine happening. What is hard to imagine, in my mind anyway, is the thought that the angle doesn't change and that there isn't some naturally created convexing, unless an angle guide is used and those are fairly recently created implements. Sloppy? I'm pretty sure master woodcrafters of centuries past didn't think so.

One other concept to keep in mind, of all the people who own and want to sharpen their knives, maybe one in a hundred can use a bench stone to get the edge they want. Most have tried, many have failed to achieve satifactory results. Everyone I know who has tried using a sander as I've described above has been successful in creating what they believe is a satisfactorily sharpened edge. In the end, that's all that matters.

So does 25 microns of steel matter? Only if you use steels that need to be sharpened every week.

 

[Uncle Timbo]

Thanks to everyone for the info. Especially you Mr. Hossum.

 

[Cliff Stamp]

Cliff, when you begin posting photographic or some other form of hard evidence instead of "here's what I've seen or measured or think", I will be willing to accept some of your premises and conclusions.

If someone wanted to fabricate data then the corresponding pictures could easily be produced. Thus it is never used as a serious source of proof but simple a means of pretty exposition. In general in a scientific debate what you do is look at the hypothesis, see if it matches existing data from other sources and the known theory. In this case this holds true very well if you look at the people studing plane blades, who have lots of pictures, as well as Verhoeven/Lee. Swaim as I have noted was the basis for the above specific details on abrasion necessary for sharpening. I have referenced these in detail on the pages I have written about these issues.

What is stated in regards to speed of sharpening is also easy to verify using basic math. How fast do you move the knife across the belt sander. Calculate how many passes this equates to on a stone. Do the math, it is a lot. This isn't opinion, it is facts and like all arguement is not relevant to the speaker aside from ad hominem issues. Do some cutting with one of your knives, does the edge visibly chip out or grossly deform. If not then this tells you that the edge damage is less than 0.1 mm because at this level you can see it by eye.

Until then they are as indeterminant as you accuse mine of being ...

No it isn't even close. I have said exactly what was done and what was observed. You have admitted you don't know what was done and are extrapolating conclusions with no supporting data and as I have shown are trivially false.

So does 25 microns of steel matter? Only if you use steels that need to be sharpened every week.

Yes because the knives I have from Johnston in 1095 at 66 HRC, O1 at 63.5 HRC, and M2 at 65/66 HRC, and from Wilson in S30V 60 HRC, 10V 62.5 HRC, Spyderco in ZDP-189 at 65 HRC, Busse Combat in INFI, Dozier in D2, etc., none of these have of course good edge retention abilities. Even though all of those knives stay sharp for quite some time, on none of them would I want to sharpen them and thrown away metal many times faster than is optimal. My Battle Mistress is extremely well used, when I am actively using it to clear lots it will be sharpened more than once a week, however even after years of use you can't tell by looking at it because I remove minimal amounts of material.

-Cliff

 

[Jerry Hossom]

Yes because the knives I have from Johnston in 1095 at 66 HRC, O1 at 63.5 HRC, and M2 at 65/66 HRC, and from Wilson in S30V 60 HRC, 10V 62.5 HRC, Spyderco in ZDP-189 at 65 HRC, Busse Combat in INFI, Dozier in D2, etc., none of these have of course good edge retention abilities. Even though all of those knives stay sharp for quite some time, on none of them would I want to sharpen them and thrown away metal many times faster than is optimal. My Battle Mistress is extremely well used, when I am actively using it to clear lots it will be sharpened more than once a week, however even after years of use you can't tell by looking at it because I remove minimal amounts of material.

I'm not sure I follow that, but if you got yourself a minimum wage job for all that time you spent "removing minimal amount of materials" while trying to get a knife sharpened, I suspect you could buy yourself another Battle Mistress.

It really wasn't a photo of you doing work that interested me. It is a photo of work done by you as evidence you actually did the work and got the results you claim that interests me. Then again, it really doesn't. The only thing that interests me is that people who like knives get as much utility and pleasure from owning their knives as is possible. Spending hours worrying over exactly how many arcseconds comprise a perfectly honed edge is just not my idea of fun. Worrying about how many years a knife will last is less important than how much pleasure one gets from using that knife for whatever number of years you may own it or have left, whichever comes first.

Sharpening a knife is easy. Let's not make it complicated.

 

[Bill DeShivs]

I don't go out to the shop and zip my knives on the 2 X 72 every time they get dull. You certainly can remove a lot of metal with the sander, but it works well on really dull knives. I finish them by hand. I went through this "ultimate sharpening" phase in the 1970s. Can someone get a knife sharper than me? Probably. Does it matter? Probably not.
It's interesting to see it done in scientific terms, but for 98% of the people out there it doesn't matter, it's purely academic. Back then we thought anyone using jig-type sharpeners was either uncoordinated or just too lazy to learn how to sharpen.
I mean, if you drive a car you have to know how to put gas in it and check the oil. Why not learn how to sharpen a knife? It isn't hard for most people. I'm amazed that they now think you have to buy a $75 sharpening system, when a $10 stone would do the same thing.
Bill

 

[Jerry Hossom]

Ya got me on that one Bill. 30+years of experience certainly helps. I just don't know 10 folks who can efficiently use a bench stone. I'm not one of them.

I would like to add that for inexperienced people using a belt grinder/sander, the 1x30" belt machine is a lot less likely to take off too much or get the blade too hot. A fixed speed 2x72 grinder is a powerful beast that can take off steel in a heartbeat. The smaller 1" wide belt and weak motor make the smaller machine a pussy cat to handle, especially with fine grit belts - just don't try to grind a knife blade with it.

 

[John Frankl]

This is a very informative thread. More than one way to skin a cat. I have a variable speed KMG, so I can better control metal removal and heat. But I like using stones as much as possible.

Early on this was written: "Custom knives are made on belt sanders!
Bill"

Yes, and no. Many very good makers refuse to use their very nice belt grinders beyond about 220 grit simply because no matter how slow you go they are not as controllable as doing things by hand. From 220 on it is all files, stones, and paper.

John

 

[db]

“
Cliff said..
If I wanted to fabricate data to prove a point I could obviously photoshop a picture. What I have said is what I have observed and it actually agrees with
published work which I have referenced in the pages I have written on the subject. It also is well supported by guys like Swaim as I noted was the basis
for the above specific details on abrasion necessary for sharpening.
Then provide a link to these references. Again you don’t even correctly refer to posts in the same thread why would anyone think you correctly use unknown references? You demand proof on every small detail from others posts demand the same from yourself.
“
How fast do you move the knife across the belt sander. You can use this to directly calculate how many passes it equates to on a stone. Do the math, it
is a lot. This isn't opinion, it is facts.
Not really it’s more misinformation. How much steel that is removed depends more on how much pressure is applied than how much of the belt moves across the edge/blade. The pressure makes much more of a difference in removing steel.
“
One of whom is using the method I developed years back to measure
push cutting sharpness.
What is this method you developed?

 

[Jerry Hossom]

John, I know a great many knifemakers and none I've spoken with stop using their grinder at 220 grit. Some do stop at 400 grit and finish by hand, but most of those do flat grinds and/or are applying a brushed or satin finish in the lengthwise direction where the grinder is of limited use.

With some experience the use of a belt grinder is easily controlled, especially using a variable speed machine. If you'd like to more safely use your 2x72 belt grinder to sharpen I'd suggest your try Norton Norax or 3M Apex belts, which use a structured abrasive that runs cooler than aluminum oxide or ceramic belts. Unfortunately these belts are not available for 1x30" machines but the belt that are available work just fine, and as I said before the smaller machine is less likely to overheat the steel.

Again, I'm not suggesting anyone stop doing what they know works for them. There is no reason to. My comments are addressed to those who want to improve their sharpening results or reduce the time they spend using another method. I'd also suggest this method as an easy way to produce a convex edge, which I and some others believe is a stronger and more efficient cutting geometry.

 

[thombrogan]

After reading a lot of this thread the other day, my otherwise trusty 1x30 Harbor Freight belt sander no longer starts. Probably the switch had gotten too loose, but what a freakish and depressing coincidence.

Jerry,

You can use one of those 1x30 sanders to make a knife, but it helps to use thin, fully hardened M2, and be very angry. And a hollow grinding rig, like a wet grinder, helps too. You just have to calm down when finishing the blade or else the scale material will break.

 

[Jerry Hossom]

Thom, if you used your 1x30 to grind hardened M2, it most likely died of exhaustion.

 

[Rich_S]

Edge up is a REALLY bad idea. A broken (cut) belt is the best that can happen.

I sharpen edge up all the time and never had any real problem. This is with Alum Ox cloth belts on a 1x42. If I sharpen edge down, I can't see what I'm doing and it comes out all cockeyed.

 

[John Frankl]

Jerry,

That's why I wrote "Yes, and no." Though I also know many who use their grinders way past 220, I also know those who don't go past 120. For the satin finished blades you are, of course, correct, but I am also talking about people who shy away from the grinder for handle and guard work as well. There are certain handle and guard looks/configurations that can never be done with a grinder. Of course, I work in and enjoy and "ABS style" so I admit that we are talking about different styles as well.

John

 

[Jerry Hossom]

Rich, I won't deny that some can sharpen edge up. I probably could. I seriously don't recommend it however. Someone could get hurt.

We're on the same page John. I'm trying to generalize for those who read this who are not experienced with belt sanders. One of the very best makers I know uses only a file and creates some of the most amazing knives I've ever seen. - Wolf Loerchner. I'm pretty certain I spelled that incorrectly.

Can you believe this was shaped entirely by hand with files and hand held abrasives?

 

[Cliff Stamp]

... all that time you spent "removing minimal amount of materials" while trying to get a knife sharpened, I suspect you could buy yourself another Battle Mistress.

It takes seconds to sharpen a knife in the manner I described because it is removing the minimal amount of materials. I spent my time working with knives, not sharpening them, this is why I have refined the sharpening I do to a bare minimum.

It is a photo of work done by you as evidence you actually did the work and got the results you claim that interests me. Then again, it really doesn't.

Of course it doesn't just like you ignore the math and the evidence presented which shows you are wrong or even think about the consequences of your comments which would also show they are trivially wrong. As I noted, if the edges on your knives actually did require significant material removal which would warrent being sanded then you would see visible damage/deformation.

Just consider even very fine stropping, ask people who actually use such wood craft knives how often they strop knives when they stop to sharpen them. Do they use a few passes or sit there going back and forth for a hundred passes. Now again do the math and see how many passes on a stationary belt your time on the belt sander equates to. Talk to any of those guys and see if they would think it would be reasonable to keep stropping over ten times as long as necessary.

If you want to see actual pictures then I have many such references provided, you have of course ignored them and the conseqeuences they imply. Several of them are in fact are on chisels specifically, and even on 3V chisels. Landes has not only noted how edges degrade but studed the nature of the behavior and graphed it and it agrees with the model I developed some time ago for edge retention and described here on the forum.

The work by the guys studing plane blades, which I have referenced in the page I wrote on blade evaluation, shows under magnification exactly how much metal is removed, it agrees exactly with what I said. There is also commentary on SwordForums by a metallurgist citing studies of a similar nature and noting the wear on edges will stabilize at the micron level.

Db, as for belt wear and time, it would be assumed of course you are using similar pressure on the belt and the benchstones. In the above, on the benchstones sharpening I noted, the force is very light, about 250 grams, this is not even the weight of a decent sized knife. Note if you actually pressed this light on a belt sander you could not even induce a sigificant curvature in the belt, you would in fact have a flat grind. So the belt sander will actually grind off faster still.

-Cliff

 

[Ben Dover]

As a fairly new person to the forum, and the hobby, it kind of breaks my heart and frustrates me to see three or four people that I have received EXCELLENT advice from, and come to respect, calling each other names.

C'mon guys, those of us who don't know one percent of what you know look to you for guidance and advice. And that's MOST of us!:jerkit:

Why can't you guys that we all look up to do your arguments by PM, and when you reach consensus, post it here so that the other 99 percent of us can benefit from it.

We are the learners. You are the teachers.