Chisel backs

[Jacob]

Jacob,

Please do not be more obtuse than you have to.

Preparation means removing manufacturers scratches and getting a nice fine finish adjacent to the edge.

It probably means grinding and honing the bevel as well.

Obtuse, moi? Clear as day I thought. :lol:
These things shouldn't take more than a minute and there is no functional reason for removing manufacturers scratches (within reason, see my link photo above).

....
Here are some of your helpful observations on honing guides.

100s of quids for a honing guide.
Plus the usual paraphernalia.
They are jealous because they can't do it.
Maybe they actually don't do a lot?
Fiddling with crazy sharpening techniques.
Wouldn't do a camber either, completely pointless.

I would say singularly missleading.

David

Good to see you are getting the idea Dave. It's never too late! What is it ypu find misleading? (only one L BTW).

 

[bugbear]

Thanks Jacob. I'll find something ussable overhere. Tradenames aren't allways easy to translate in Dutch, which makes it difficult to get the stuff recommended on an English forum. But I'll look around in the kind of places you mention.

There sure is a lot more to grit then the micron size. The shape of the grit, how it is embedded in the carrier and how deep. And how it wears. In man made stuff it is easier to compare, but natural stones behave quite a bit different.

Quite right in all regard; although grit size is probably the most important factor, the other factors play a part.

For hacking away tool steel, I recommend the zirconium belts which the metalwork industry uses.

Norton term it "Zirconia", but I've also seen "Zirconium" and "Zirconium Oxide". Great stuff.

BugBear

 

[Corneel]

I'll keep an eye out for Zirconia too.

Anyone experience with diamondplates for this purpose? Something like this iWood plate isn't too expensive:
http://www.toolsfromjapan.com/store...roduct_info&cPath=335_462_463&products_id=852

 

[Jacob]

Also most common as Silicon Carbide http://en.wikipedia.org/wiki/Sandpaper

Best for flattening (plane soles in my experience but chisels too if you must) is coarse wet n dry paper flooded with white spirit on a machine table. If the paper is paper backed and flat, the white spirit keeps it down and also helps with the abrasion. For a bigger area you can put pieces edge to edge.
60 grit is all you need really, but it helps to take off the snatchiness with a quick pass over your finest, say 400 grit. This leaves the scratches in place but reduces friction by taking the edge off the scratches. Further polishing is just cosmetic and not necessary.

 

[woodbrains]

That would explain why it doesn't last very long on metal. I'll search a little further for the right stuff.

I use Japanese stones. The 400 is from Bester, very agressive stone. But I don't know the grit size.

Hello,

Japanese 400 stone is slightly finer than P400 sandpaper in European standard. ( 32 micron compared to 35 ). I don't know what grit paper you were using before you moved to your stone, but I would say that you should not be expecting to remove much metal on a stone like that, just removing scratches from the coarser grit. If you still have some metal to remove, you should still be on coarser grits.

You describe the paper as turning into a finer grit as you progress. This is classic firiability of Ali oxide paper, so I suspect this is what you ar e using. Si C does not break down like Ali Oxide and is harder. It will wear out, but takes longer to do so, and the particles do not reduce in size. So 80 grit remains 80 grit, it just gets less effective as time goes on. As a point of interest, the grains of abrasive are rounder as produce 'U' shaped scratches whereas Ali Oxide is pointy and due to its friability, continues to break down into smaller pointy particles, so the scratch pattern is sharper, and continually getting finer as you progress. It doesn't make much practcal difference, but this is what happens. Ali Oxide is less useful for metal.

Mike.

 

[Corneel]

You are right of course. But that still leaves me with the problem of mismatch between the surface grinded on the sandpaper and the surface the stone wants to grind. Nobody else have this problem? I like restoring old tools, grinding out pitted backs is a common occurence for me. Yet I haven't found yet a system that makes it a quick and easy job.

 

[woodbrains]

Hello,

Go on to finer grits on the sandpaper before the stone. I f you used P 320 as a final paper then 400 stone so the leap in grits is small.

Mike.

 

[bugbear]

Hello,

Go on to finer grits on the sandpaper before the stone. I f you used P 320 as a final paper then 400 stone so the leap in grits is small.

Mike.

These list are VERY helpful:

http://sharpeningmadeeasy.com/grits.htm
http://www.metalclayuk.co.uk/asp/MicronsGrits.asp
http://www.fine-tools.com/G10019.htm
http://www.evenfallstudios.com/metrolog ... isons.html

Especially if you mix your abrasives (diamond, waterstones, SiC paper etc)

As discussed elsewhere, grit size is not the only factor, but it's the dominant factor.

BugBear

 

[Corneel]

Bugbear, At the end of your first link, there is another link to a very interesting chart.
http://sharpeningmadeeasy.com/speed.htm
I suppose this graph is about stones? SiC is A carborundum stone probably, AlOx an India stone? Even a 1000 grit waterstone seems to be faster then any carborunmdum stone.

 

[Jacob]

I'd be fairly sceptical of graphs like this one. Knife sharpeners are even madder than woodwork tool sharpeners and even more awash with pseudo science.

 

[bugbear]

Bugbear, At the end of your first link, there is another link to a very interesting chart.
http://sharpeningmadeeasy.com/speed.htm
I suppose this graph is about stones? SiC is A carborundum stone probably, AlOx an India stone? Even a 1000 grit waterstone seems to be faster then any carborunmdum stone.

Yes - "Crystolon" from Norton is SiC whilst "India" is AlOx.

BugBear

 

[Corneel]

I'd be fairly sceptical of graphs like this one. Knife sharpeners are even madder than woodwork tool sharpeners and even more awash with pseudo science.

I'm not so sure. Maybe not the exact numbers, but my 400 Bester waterstone is definitely way faster then the Carborundum stone or the coarse India I have. So the trend this graph indicates isn't totally hogwash. Keeping the stones clean helps, but still...

You pay for this speed, but as long as I'm not on the dole, I don't really care.

 

[woodbrains]

I'd be fairly sceptical of graphs like this one. Knife sharpeners are even madder than woodwork tool sharpeners and even more awash with pseudo science.

Hello,

This graph looks pretty much spot on to me, having used most of the media shown, I would pretty much agree with everything. It is pretty much universally recognised that artificial Japanese waterstones have the greatest speed of cutting and the finest finish, when used in the right combination.

Mike.

 

[custard]

I sometimes think we play at being scientific and objective when it comes to sharpening, but we can't actually break away from an almost superstitious "shiny equals sharp" mindset.

In an effort to get away from the need to constantly flatten water stones I tried using DMT diamond stones. I used a Red (600 mesh/25 micron) and a Tan (8000 mesh/3 micron).

The problem was the 3 micron stone didn't produce a polished bevel, I tried it with a variety of plane blades and in all honesty found it very difficult to tell if it was less sharp in actual usage than a polished water stone edge, but for the life of me I could never bring myself to lay the backs of my chisels onto the 3 micron diamond stones, knowing it would eradicate the mirror polish. So I went back to water stones!

Logic tells me that the vast majority of the sharpening fetish is just hocus pocus, and that in practise any amazing edge breaks down in just a few strokes of the tool and you then settle down to 90% of the usage life until the next sharpening being at the "acceptably dull" level rather than the initial "scalpel sharp" level. But logic flies straight out of the window when I'm trying to deliver a flawlessly dovetailed drawer, I become as superstitious as a fisherman and want the comfort blanket of the mirror edge.

On a related point I strongly suspect that stropping actually dubs over an edge and is a retrograde step, but stropping will always have supporters when "shiny equals sharp" is actually the real litmus test that we're all secretly applying.

 

[woodbrains]

Hello,

Dear Custard, what grade of waterstone were you using? Diamond plates when new are pretty aggressive, but settle down to less aggressive and 'softer' edged, so probably would do more like you were expecting after some use. However, 8000 Japanese waterstones are finer, so might account for the different level of polish expected, too. As I said earlier American and Japanese systems are not directly comparable.

Stropping really only has a benefit for oilstone users, as the finest stones are coarser than the finest Waterstones. I don't think the edge is dubbed exactly, but the effective angle is increased and by the nature of the soft strop, the very tip is slightly convex, which makes it look like it is dubbed. Polish is still an abrading excersise, just that the scratches ar finer and not as easy to see, reflecting more direct light, rather than scattering it.

Edges sharpened with finer grits do last longer as the grains of the steel are less fractured to start with and therefore do not crumble so quickly.

Mike.

 

[Jacob]

....."shiny equals sharp" i.....

More importantly, shiny means less friction - where it counts and there is a lot of pressure on the steel from either side of the cut close to the edge.

....Stropping really only has a benefit for oilstone users, as the finest stones are coarser than the finest Waterstones.....

There is no particular limit on the fineness of stones you can put oil on.
Stropping is for polish (see above) with the advantage that the flexibility of the leather reaches more of the blade. Without stropping - if the shape of a blade doesn't exactly match a stone then you won't get a thorough polish - hence the obsession with flatness. No different from polishing a brass letter plate - if you did it with Brasso on a piece of wood it wouldn't reach into the dips

 

[custard]

what grade of waterstone were you using?

Mike.

I generally use Shapton stones, I have them in 1000, 4000, 8000, 15000, and 30000 grits. Which raises an interesting point that I think supports my "shiny equals sharp" sceptics view.

Edges begin to look polished to our eyes at about 8,000 grit. And guess what, by common consent this is regarded as the optimum level of sharpness. However it's possible to go much finer, either with Shapton stones, other brands of water stones, or diamond pastes. But our eyes can't readily perceive any enhancement after about 8,000 so very few people bother sharpening beyond this.

It strikes me as an altogether improbable co-incidence that optimum sharpness just happens to be the point where our eyes first begin to perceive a polished surface!

The wood couldn't care less about polish, neither does the tool, it either cuts cleanly or it doesn't. But the magpie in us is attracted to, and satisfied by, a shiny edge. So we've generally settled on 8,000 grit when for all I know 4,000 grit or 15,000 grit may actually make better empirical sense.

This is the point I'm trying to make, I suspect 8,000 grit is significant more for the psychological reason that it's the "moment of first polish", than for any scientific rationale.

 

[Kalimna]

Custard - I am interested to know your thoughts on th 15/30k shapton stones. Do you perceive a finer edge (in use) when sharpened to the higher grits? The finest I have is a 12k King stone (I think it is King, may not be), and I think that is where funds stop. I am not sure I could persuade the inner magpie to go for the 30k stone, however much of an improvement it is.

Cheers,
Adam

 

[custard]

Custard - I am interested to know your thoughts on th 15/30k shapton stones. Do you perceive a finer edge (in use) when sharpened to the higher grits?

Hello Kalimna, as far as plane blades are concerned no is the simple answer, neither in quality of the cut nor in longevity of the edge! But I'm not sure I actually perceive much of an improvement beyond 4000 grit, which is below the "polish threshold".

Here's the thing though; a well executed, needle point, half lap dovetail is just, but only just, within my abilities. On a good day I'm happy with them, on a bad day they look terrible. So like a fisherman venturing beyond the sight of land in the days of sail, I'm easy prey for superstitious nonsense! Consequently before attempting an important drawer I'll sharpen my chisels all the way to 30,000 grit, in earlier times I might have thrown salt over my shoulder or checked for black cats in the workshop!

 

[woodbrains]

....."shiny equals sharp" i.....

More importantly, shiny means less friction - where it counts and there is a lot of pressure on the steel from either side of the cut close to the edge.

....Stropping really only has a benefit for oilstone users, as the finest stones are coarser than the finest Waterstones.....

There is no particular limit on the fineness of stones you can put oil on.

Hello,

Of course you could put oil on a fine waterstone and ruin it. But in the realms of stones meant for sharpening with oil, they are generally not as fine as those meant for water.

Abrading metal with brasso is still sharpening, but you have to get to the point where the brasso will remove the scratches left by the previous grit. Brass is not sharpened in the strict sense in that it is not a hardened edge tool, but brasso will not polish it, either, until the brass was abraded with a sufficiently fine abrasive before hand. There is no difference between sharp or polished, but a semantic one. If an edge tool is abraded with a finer grit it will be sharper and have a higher polish. Whether the grit is fine beyond the point of making a reasonable difference to tool performance does not dictate as to where sharpening stops and polishing takes over; they are one and the same. We have to decide ourselves the practical limits when we work.

This nonsense about reducing friction has already been de bunked by the carvers who tell us they strop to acheive the ultimate sharp edge. A very sharp tool will have the least friction anyway. A roughly honed tool that is stropped wil still be a roughly honed tool, and cut the wood no better, it will just have slightly shinier but similarly rough scratches. it would be better to go to a finer stone and miss out the strop, if the number of sharpening stages were a consideration. Stropping a tool that has not been sufficiently finely honed is a waste of time. Stropping a dull tool is a waste of time. This was all said only a few days ago, but memories are very short, apparently.

Mike.