removing a back bevel

[Jacob]

....
The better wearing edge is only a feeling I've got, but not a theoretical one entirely. Over more than 30 years of sharpening, I have a notion that there is some sort of longer lasting edge from a consolidated sharpening than a purely abraded one. It is just that there are so many variables from blade to blade and in working characteristics from wood etc. etc. that I think it has yet to be conclusively proved. Could even one woodworkers lifetime be a big enough survey to prove a point, unless one goes down the route of making the test the sole objective. I want to work wood not test steel exclusively, which is why other perspectives might show a trend.....

It (whatever it is) will never be proved, for the reason you give (too many variables) and also because it doesn't seem to have much bearing on the practical needs of a working woodworker i.e. sharpening isn't much of a problem.
No need to devote a woodworkers lifetime to the topic - we have the experience of generations/millions of woodworkers to fall back on.
Personally I think this thread has reached escape velocity and is well on the way to another planet!

 

[woodbrains]

Hello,

Ahh, but Jacob, of all the millions of past woodworkers from which to draw knowledge, no one that I am aware of, has ever put forward the idea that sharpening on certain media might actually increase the longevity of the sharpened edge. It is clear, despite resistance from a few here, that metal is persuaded to move about, whilst in a plastic state. Couldn't this work harden the edge? Bending a piece of steel causes the same plastic state, the grains are moved and realigned, and the steel at the bend is hardened enough to prevent it being bent back. The reason I am not saying it definitely hapens is because I only feel there has been a tendancy for fine oilstone sharpened tools to hold their edges longer. I thought up the idea of work hardening to explain what I was experiencing. Since I know quite well that Bugbear is correct in his assumption that a quantitative test would be needed and would be 'tricky' I was hoping for a few others who might have experienced similar to explain what they have observed.

Mike.

 

[bugbear]

Hello,

Ahh, but Jacob, of all the millions of past woodworkers from which to draw knowledge, no one that I am aware of, has ever put forward the idea that sharpening on certain media might actually increase the longevity of the sharpened edge.

Well, there's this careful experiment, by the UK Forest Products Research Lab.

http://www.amgron.clara.net/page72.html

But I think the experimental design assumes that grit size is an adequate measure.

It does show that finer edges do last longer,
which is a slightly counter intuitive but very gratifying result.

BugBear

 

[MMUK]

May as well break out the BBQ and the popcorn guys, this one's going for a while.....

 

[Corneel]

So, I could look up some interesting articles today on burr formation. The most interesting one is this one:

http://ac.els-cdn.com/S000785060760...t=1398150907_6565a83e1710f5de5d6a90a1c8c94608

If you can't download the PDF, but are still very much interested, send me a PM.

They studied burr formation when using a reciprocating surface grinder. A big grinding wheel is penduling over the top surface of a metal block. One thing completely different from our use is that they actually leave the surface with the grinding wheel, while we keep the iron all the time in contact with the grinding stone. Another difference is the much higher speed and higher temperatures, despite the use of coolant.

I don't understand everything, but plastic zones play a role. The metal becomes plasticy and can be smeared out. This plastic zone is increased under higher temperatures.

An interesting sentence from the article:
A section at the end of the exit edge, which is theoretically removed by the wheel depth of cut, remains at the edge. The burr is develloped mainly by this uncut section.

So, in other words, the small bit at the very edge isn't removed by grinding, but becomes plastic and is elongated, out of reach from the grinding wheel and folds over the edge.

Another factor is the angle of the edge. The very acute angle we are grinding gives much less support, so burrs are larger.

The high temperatures at the edge, due to the grinder speed cause local hardening. This means that the edge reaches temperatures above 800 degrees. I don't believe that is a factor in grinding an iron on a sharpening stone by hand. Not even on an oil stone, where the fluid cools much less effective then on a waterstone.

I think everyone was a little bit correct and a little bit wrong in explaining the burr. Some part of the formation of the burr comes from moving metal from the bevel side through plastic deformation. But the acute angle of the edge also leads to a larger burr, through lack of support, so some material from the edge itself is bended too.

Any way, I think we can safely conclude that you can feel the burr before enough material is removed to form a perfect pointy edge. But that is unavoidable, the burr is a serious deformation of the edge, and grinding for a longer time isn't going to change that. The only way to reach an aproximation of a perfect point edge is using finer abrassives.

 

[Jacob]

Hello,

Ahh, but Jacob, of all the millions of past woodworkers from which to draw knowledge, no one that I am aware of, has ever put forward the idea that sharpening on certain media might actually increase the longevity of the sharpened edge. ...

I think they would have hit on it by now, if there was any practical value in the idea.
They have of course put a lot of effort into increase the longevity of the sharpened edge mainly by metallurgical development and design details such as laminating, right from day one (end of the stone age).

 

[woodbrains]

But I think the experimental design assumes that grit size is an adequate measure.

It does show that finer edges do last longer,
which is a slightly counter intuitive but very gratifying result.

BugBear

Hello,

I realise finer edges last longer, I have always thought so, but I'm actually talking about the stone possibly modifying the grain structure of the steel to add hardness, too.

Mike.

 

[woodbrains]

I think they would have hit on it by now, if there was any practical value in the idea.
They have of course put a lot of effort into increase the longevity of the sharpened edge mainly by metallurgical development and design details such as laminating, right from day one (end of the stone age).

Hello,

You are assuming things are static and nothing new can be found, which is a narrow minded point to make. Metallurgical development is advancing continually, so why can't we? After all, very few of us actually still use steel as it was 100 years ago except for the antique tool users, no modern steel is like it used to be. We all have to advance as new products advance.

Mike.

 

[Jacob]

I think they would have hit on it by now, if there was any practical value in the idea.
They have of course put a lot of effort into increase the longevity of the sharpened edge mainly by metallurgical development and design details such as laminating, right from day one (end of the stone age).

Hello,

You are assuming things are static and nothing new can be found, which is a narrow minded point to make. Metallurgical development is advancing continually, so why can't we? After all, very few of us actually still use steel as it was 100 years ago except for the antique tool users, no modern steel is like it used to be. We all have to advance as new products advance.

Mike.

OK Mike - let us know when you get there!

 

[MIGNAL]

I use steel from over 100 years ago. I use steel made a few months ago. I don't notice much difference at all. Get the things sharp and off you go!

 

[Trafalgar]

I think they would have hit on it by now, if there was any practical value in the idea.
They have of course put a lot of effort into increase the longevity of the sharpened edge mainly by metallurgical development and design details such as laminating, right from day one (end of the stone age).

Hello,

You are assuming things are static and nothing new can be found, which is a narrow minded point to make. Metallurgical development is advancing continually, so why can't we? After all, very few of us actually still use steel as it was 100 years ago except for the antique tool users, no modern steel is like it used to be. We all have to advance as new products advance.

Mike.

Mike, but what does this advancement actually look like in the context of a serious hobbyist's or professional shop? As far as I can tell it means spending more money on highly engineered sharpening media combined with much more intricate methodologies - multiple bevels, back bevels, etc. While the edges may last marginally longer, I don't believe there is any proof that the surface quality achieved, on an actual article of furniture, is any better than that of 250 years ago.

Edge longevity is being oversold because it's the only thing to sell. And improvements in it are clearly at the margin, regardless of what the tool manufacturers and their advance-men tout. One usually spends more time sharpening these new steels or is forced to buy new media to sharpen it. Seems like practically a wash to me.

 

[Jacob]

I think edge longevity has become a priority since sharpening itself became so prolonged. All that effort and the thing needs doing again a few minutes later!
No prob for a trad sharpener* but hell if you've got to get all your kit out, flatten stones, etc etc. :lol: :lol:

*no prob, even a good thing to keep having to freshen up an edge, as long as it's easy to do.

 

[Racers]

The quest for knowledge is a good thing, admittedly some times it can focus on a very narrow field but that's still a good thing.

So I hope this thread dose carry on in the recent vein, its very thought provoking and interesting.

Pete

 

[woodbrains]

Mike, but what does this advancement actually look like in the context of a serious hobbyist's or professional shop? As far as I can tell it means spending more money on highly engineered sharpening media combined with much more intricate methodologies - multiple bevels, back bevels, etc. While the edges may last marginally longer, I don't believe there is any proof that the surface quality achieved, on an actual article of furniture, is any better than that of 250 years ago.

Edge longevity is being oversold because it's the only thing to sell. And improvements in it are clearly at the margin, regardless of what the tool manufacturers and their advance-men tout. One usually spends more time sharpening these new steels or is forced to buy new media to sharpen it. Seems like practically a wash to me.

Hello,

Despite others commenting to the contrary,(how do they know?) mine and most people's sharpening regimen is quite simple. I use 2 stones and a grinder. I started with oilstones and then switched to Japanese waterstones. Still just 2 stones. I don't want to go down the line of debating sharpening stones, this has been done ad nauseum. But don't mistake a questioning attitude with unnecessary complication.

I also use old tools and lots of different new steels too. There are subtle and noticeable differences in them all. For instance A2 steel does produce a more tenacious burr than old cast steel or T10 or O1. Ultimately it does not matter too much, my method of removing the burr leaves a clean, sharp edge, but the difference is there and it does indicate performance differences in the steel.

Mike.

 

[bugbear]

I think edge longevity has become a priority since sharpening itself became so prolonged. All that effort and the thing needs doing again a few minutes later!
No prob for a trad sharpener* but hell if you've got to get all your kit out, flatten stones, etc etc. :lol: :lol:

*no prob, even a good thing to keep having to freshen up an edge, as long as it's easy to do.

In order to help you, I'll gladly swap an ordinary 2" Stanley plane blade
for your laminated one (Smoothcut or Samurai I imagine) - I'll even pay the postage.

I'd hate to think of you missing out on all that "freshening" due to
having an edge with unnecessary longevity.

BugBear

 

[Jacob]

I think edge longevity has become a priority since sharpening itself became so prolonged. All that effort and the thing needs doing again a few minutes later!
No prob for a trad sharpener* but hell if you've got to get all your kit out, flatten stones, etc etc. :lol: :lol:

*no prob, even a good thing to keep having to freshen up an edge, as long as it's easy to do.

In order to help you, I'll gladly swap an ordinary 2" Stanley plane blade
for your laminated one (Smoothcut or Samurai I imagine) - I'll even pay the postage.

I'd hate to think of you missing out on all that "freshening" due to
having an edge with unnecessary longevity.

BugBear

You've missed the point somewhat. The laminated Smoothcut, Record, Stanley, etc speed up sharpening by having softer metal behind. Really noticeable with the Smoothcut - as you dip the blade the soft backing really drags on the stone as a lot of metal is (more easily) removed.
And the second reason modern sharpening is more prolonged is the fashion for pointlessly thick blades.

 

[bugbear]

I think edge longevity has become a priority since sharpening itself became so prolonged. All that effort and the thing needs doing again a few minutes later!
No prob for a trad sharpener* but hell if you've got to get all your kit out, flatten stones, etc etc. :lol: :lol:

*no prob, even a good thing to keep having to freshen up an edge, as long as it's easy to do.

In order to help you, I'll gladly swap an ordinary 2" Stanley plane blade
for your laminated one (Smoothcut or Samurai I imagine) - I'll even pay the postage.

I'd hate to think of you missing out on all that "freshening" due to
having an edge with unnecessary longevity.

BugBear

You've missed the point somewhat. The laminated Smoothcut, Record, Stanley, etc speed up sharpening by having softer metal behind.

In my experience the edges on the Japanese blades greatly outlast the edges ordinary Record/Stanley, hence my friendly and helpful offer.

BugBear

 

[Trafalgar]

BugBear[/quote]
You've missed the point somewhat. The laminated Smoothcut, Record, Stanley, etc speed up sharpening by having softer metal behind. [/quote]

In my experience the edges on the Japanese blades greatly outlast the edges ordinary Record/Stanley, hence my friendly and helpful offer.

BugBear[/quote]

Honing and stropping an edge that has just gone off takes two to three minutes, tops. Let's say you save four of these rehonings per working day by having Japanese blades (or the new steels) whose edges "last longer." That's a savings of less than fifteen minutes per working day.

Other than for a rare few, I frankly doubt that anybody planes that continuously, day in and day out, for any of this to even come into play on a realistic basis.

Edge longevity is oversold. It is being put forth as a quality marker when in fact none of these steels take a better edge, if even as good an edge, as plain high-carbon steel. It's all sales puffery. People are being sold edge longevity when they don't even use the tools enough for it to matter. And even if they did it still doesn't matter. They would barely save enough time for one good smoke break or break for tea. It's all so silly.

 

[Cheshirechappie]

Just thinking out loud, as it were.

I wonder if the particle shape of the abrasive has a significant effect?

A stone made up of hard, sharp-edged particles would tend to act mostly as a cutting tool, shearing metal off the sharpened surface, leaving gullies and peaks on the abraded surface. A stone made of hard, rounded particles wouldn't cut so much, it would burnish a sharpened surface by smearing metal (plastic deformation) - perhaps tending to compress the high points left by the previous stone into the gullies it leaves as well.

So, whilst the abrasive particles of the two stones may be of similar size, the two stones would behave very differently in sharpening, and give different edge qualities. One rather cut and ragged, the other more burnished or polished.

 

[Richard T]

So ... Danny, how are your chisels coming on?