Chisel Sharpening - Subtleties in Flattening Backs

[vaj]

Hi all. This is just to share some fairly esoteric thoughts/a recent discovery in respect of flattening chisel backs.
I've been doing a lot of fine paring of the sides of large mortices in beech recently to fine tune fits as a part of a bench build (stretcher joints) and found that my Japanese chisels while performing very well were behaving as though there was a tiny bevel on the back.
As in needing to be tilted up by the tiniest hair to get them to cut to remove very small irregularities when paring an otherwise flat surface - or to cut exactly flush/in plane when paring off a guide block.
The effect really only became obvious when paring using a guide block.
This was despite the backs having been carefully prepped on accurately flattened (via very frequent use of a 400 grit Atoma diamond plate) Shapton waterstones.- finishing with a few strokes on a hard leather strop glued to a wooden back. (flat on the leather in the case of the backs)
The resulting backs looked perfectly flat with no visually detectable irregularities near the edge. The chisels were extremely sharp.
It wasn't a big deal, but having concluded that there had to be some sort of a very tiny micro bevel on the backs and that if so it was probably happening on the waterstones it seemed to make sense to try a light further flattening via few strokes on a very fine and very flat 1200 grit Atoma diamond plate - it's similar in roughness to a 1000 grit waterstone.
This done the backs were then brought back up to 12000 with a few strokes each on successive waterstones in the usual way - but taking care to ensure that all slurry was first washed off after flattening. Then finish sharpened and given the usual few light strokes on the strop.
The difference was significant with the chisels instantly shearing off the tiniest of irregularities when paring. To the point in fact where care was needed when working a flat surface to ensure that it didn't bite and cut where it wasn't intended to.
It's not a big deal and there could be places where it's even helpful to have to tilt a paring chisel up a hair to get it to cut - but it was very noticeable how much difference this made.
My guess is that when flattening chisel backs on even very carefully flattened waterstones a wave of slurry builds up in front of the edge which causes the tiniest of micro bevels - that this does not happen on the diamond plate...

 

[Cabinetman]

Well it’s sharpening so likely to be contentious. Also everyone’s views are different.
Personally I think you are definitely overthinking things. The insides of a Mortice joint are probably better not being too smooth imo. I’ve never understood the desire to sharpen to such fine levels, if it starts to not cut, its a quick rub on a 380 combination stone slap it on my jeans a couple of times and back to work. And that’s top quality fine furniture work btw.
Ian

 

[Woodbloke]

Well it’s sharpening so likely to be contentious. Also everyone’s views are different.
Personally I think you are definitely overthinking things. The insides of a Mortice joint are probably better not being too smooth imo...... And that’s top quality fine furniture work btw.
Ian

Agreed - Rob

 

[Lurker]

Because it often ends in arguments, we have an unwritten rule hereabouts that sharpening isn’t discussed.
Whatever floats your boat, but not here.

 

[vaj]

Well...
I can safely say that you won't be arguing with me.
The feedback is tabled for what it's worth - the hope however was that it might actually be useful to somebody
The paring requirement arose out of a need to marginally re-locate the reference face of some mortises which ended up having been cut a little small on the mill.
It's a sad state of affairs if as a consequence of repeated inability to conduct a friendly and co-operative discussion that a core topic such as sharpening is ruled out of bounds on a hand tool forum...

 

[AJB Temple]

I agree vaj. There is no need to fall out about sharpening. That said I agree with Ian. With mortices there has to be enough room for the glue (and sometimes a hidden wedge) and as soon as glue is added the wood will swell and negate any super accuracy in cutting. If I want to be really sure of a tight mitre I will slope the ends of the mortice (wider at depth) and wedge the tenons into slots. When you do that they are tight and there forever.

 

[Lons]

...............It's a sad state of affairs if as a consequence of repeated inability to conduct a friendly and co-operative discussion that a core topic such as sharpening is ruled out of bounds on a hand tool forum...

It doesn't happen on here Ian but having seen it on another forum where arguments have got really nasty and way out of hand on many occasions it's a sensible rule to keep this forum mostly friendly and on good terms.

 

[vaj]

A pity I think - but I'll be lying low.

 

[Richard]

A pity I think - but I'll be lying low.

It's best to do that.

I never take part in sharpening threads for reasons already given, i.e., bitter and fractious disagreements.

Oh, darn, I just have joined a sharpening thread.

You'll have noticed I've said nothing about sharpening which is the key to keeping the peace.

But I can throw this Lesson in Sharpening in for your amusement. Slainte.

 

[Mike G]

I'm quite happy to discuss sharpening, and there is no rule against it. We're the sensible grown-ups in the room, and can easily have a conversation on most subjects without falling out. My tuppence ha'penny on the OP is that waterstones seem to me to be more trouble than they're worth, but if they work for you, that's great. I manage with chisels sharpened to 1200 on diamond plates, and then stropped. My mortices are as good as I want them:

 

[TrimTheKing]

Chaps let's not scare off new members with this , we have no written or unwritten rule on sharpening. We know what's happened in other places and it's been made very clear here that the same won't be allowed to happen, but because of that everyone knows the boundaries.

I'm conscious that a lot of people new to woodworking don't know anything about sharpening and without help and advice from us, may never learn.

Keep it factual, pros/cons etc, and we're all good. It's when people start espousing that their way is better we get into issues.

FWIW, observation from the OP, @vaj could it not be that even though the strop is hard leather, there's enough give in it to deform around the cutting edge thus creating the micro back bevel you suspect...?

 

[Woodbloke]

But I can throw this Lesson in Sharpening in for your amusement. Slainte.

I remember chortling over that piece many moons ago. My Norris A1 panel plane is similar to that one but not quite as posh - Rob

 

[TrimTheKing]

I remember chortling over that piece many moons ago. My Norris A1 panel plane is similar to that one but not quite as posh - Rob

Brilliant!

 

[Cabinetman]

Very funny indeed. I don’t actually remember being taught to sharpen tools apart from in the shed with Dad, even when I arrived at Teacher training college I think it was just assumed we could do it.
I do remember a friend of about 13 showing me how he sharpened a chisel- both sides like a penknife lol, my Dad wasn’t at all impressed!

 

[Lurker]

I sincerely apologise for poking my oar in. I genuinely believed that the forum had an unwritten rule about this subject.

 

[TrimTheKing]

I sincerely apologise for poking my oar in. I genuinely believed that the forum had an unwritten rule about this subject.

No need to apologise mate. We do have the unwritten rule about nobody being a kn0b head about it, but sensible conversation on most topics is fine so long as it stays sensible.

 

[Woodbloke]

I sincerely apologise for poking my oar in. I genuinely believed that the forum had an unwritten rule about this subject.

Your penance L is to write an on-line dissertation on the merits or otherwise of the 'rounded bevel' - Rob

 

[Blackswanwood]

Am I mistaken in thinking that sharpening Japanese tools on a diamond plate can be problematic? I thought (based on something I read on the Workshop Heaven website) that as they are made with laminated steel there is a risk that the softer steel layer ruining the plate?

I have just been given a Japanese chamfer plane as a gift so would be good to know if there is anything in it.

Cheers

Robert

 

[johnward]

I experienced unpleasant posts on sharpening at the other place but here it's much more friendly and and serious when discussed, so I for one find good posts on the subject very welcome.

 

[duke]

Hi all. This is just to share some fairly esoteric thoughts/a recent discovery in respect of flattening chisel backs.
I've been doing a lot of fine paring of the sides of large mortices in beech recently to fine tune fits as a part of a bench build (stretcher joints) and found that my Japanese chisels while performing very well were behaving as though there was a tiny bevel on the back.
As in needing to be tilted up by the tiniest hair to get them to cut to remove very small irregularities when paring an otherwise flat surface. The effect really only became noticeable when paring using a guide block.
This was despite the backs having been carefully prepped on accurately flattened (via very frequent use of a 400 grit Atoma diamond plate) Shapton waterstones.- finishing with a few strokes on a hard leather strop glued to a wooden back. (flat on the leather in the case of the backs)
The resulting backs looked perfectly flat with no visually detectable irregularities near the edge. The chisels were extremely sharp.
It wasn't a big deal, but having concluded that there had to be some sort of a very tiny micro bevel on the backs and that if so it was probably happening on the waterstones it seemed to make sense to try a light further flattening via few strokes on a very fine and very flat 1200 grit Atoma diamond plate - it's similar in roughness to a 1000 grit waterstone.
This done the backs were then brought back up to 12000 with a few strokes each on successive waterstones in the usual way - but taking care to ensure that all slurry was first washed off after flattening. Then finish sharpened and given the usual few light strokes on the strop.
The difference was significant with the chisels instantly shearing off the tiniest of irregularities when paring. To the point in fact where care was needed when working a flat surface to ensure that it didn't bite and cut where it wasn't intended to.
It's not a big deal and there could be places where it's even helpful to have to tilt a paring chisel up a hair to get it to cut - but it was very noticeable how much difference this made.
My guess is that when flattening chisel backs on even very carefully flattened waterstones a wave of slurry builds up in front of the edge which causes the tiniest of micro bevels - that this does not happen on the diamond plate...

What I am about to say will be appalling to some but! I like all means and ways of sharpening , on job sites I have flipped over the belt sander to sharpen chisels.

 

[Lurker]

What I am about to say will be appalling to some but! I like all means and ways of sharpening , on job sites I have flipped over the belt sander to sharpen chisels.

Well my way (the ONLY true way!!) is closer to you than the stones hewn by Japanese virgins fraternity.

 

[Woodbloke]

Am I mistaken in thinking that sharpening Japanese tools on a diamond plate can be problematic? I thought (based on something I read on the Workshop Heaven website) that as they are made with laminated steel there is a risk that the softer steel layer ruining the plate?

I have just been given a Japanese chamfer plane as a gift so would be good to know if there is anything in it.

Cheers

Robert

Complete tosh. When I bought my coarse diamond stone for the Tormek I emailed the company and asked the very same question; they replied saying it didn't make any difference and it was fine to grind Japanese chisels on the diamond stone. Matt Platt is out of his tree on this one - Rob

 

[Cabinetman]

Serious question, only tried one Japanese chisel and only for a short period, what happens when you sharpen it back to the big scollop on the back of the chisel? Is it indicative that all the good steel has been used?
Ian
Ps, why is the scollop there pls?

 

[Woodbloke]

Serious question, only tried one Japanese chisel and only for a short period, what happens when you sharpen it back to the big scollop on the back of the chisel? Is it indicative that all the good steel has been used?
Ian
Ps, why is the scollop there pls?

Japanese steel is a lot harder than 'normal' stuff used for chisels which is good but it's also a lot more brittle so care is needed or the edge will chip out quite unexpectedly. The scollop or 'ura' is there to remove a lot of steel so that flattening/polishing the back takes less effort. When the honed edge gets perilously close to the ura, the user needs to use a coarse stone to wear away some of the steel on the back so increasing the distance and then the honing cycle begins all over again - Rob

 

[Mike]

Serious question, only tried one Japanese chisel and only for a short period, what happens when you sharpen it back to the big scollop on the back of the chisel?

I asked the late David Charlesworth the same question and he didn't know. He held up two of his Japanese paring chisels for comparison. He had been using one for over 20 years and the other was new. The backs were nearly the same.

 

[Woodbloke]

I asked the late David Charlesworth the same question and he didn't know. He held up two of his Japanese paring chisels for comparison. He had been using one for over 20 years and the other was new. The backs were nearly the same.

If you care to look at old, well used Japanese chisels on the Bay of Fleas you ought to be able to find a few ( I did) where the blade is almost just a stump. For them to be used that much the backs must have been periodically flattened on a coarse stone to reduce the length of the ura - Rob

 

[Cabinetman]

Thanks @Woodbloke that makes sense. I’ve wondered for years.

 

[AJB Temple]

I quite like sharpening. Its therapeutic sharpening my kitchen knives. I regularly have a sesh. The single bevel good quality handmade Japanese ones are really easy. Some of my western knives less so, especially stainless steel, although the Gustav Emil Ern ones are good. Henckels much less so. Every so often I kind of lose the knack with those and turn into an incompetent that any of you would laugh at. Not quite sure why this ineptness appears. And I've got one knife, a folder, a PUMA in fact with the hardiness test impression, that I bought when I was about 17 and have never once been able to get it properly sharp.

My dad taught me to sharpen chisels and plane blades when I was around 7. We used an oil stone and some kind of thin oil in a dispenser with a flexible tube. Stropping was done on an ancient leather belt or maybe piece of harness that was some part of my grandfathers WWI army kit. Sharpening stuff, including shears and scythes, was routine, quite easy and no big deal was ever made of it. I still have those chisels, plane, oil stone and strop and still use them sometimes. Think I may even have the oiler as well. Every method works.

 

[vaj]

I'm tentatively coming back in....
My post was to share a finding.
I make no claim to superior knowledge, and won't be arguing about any of the following - we each have to find our own route in these matters.
Constructive input is of course welcome.
I've been sharpening since I was about 10 years old (am now retired for several years) starting without advice from anybody (naively) on a hollowed old oilstone on an old wooden smoother - neither of which for want of correct technique I got great results from. There's been a lot of water under the bridge since then.
Japanese chisels (white steel in both long handled paring and chopping formats in this case) are excellent in my experience - although there may be some about right at the bottom of the price range which are not the real thing so far as quality of the steel is concerned.
As described elsewhere there's a layer of very hard high carbon steel which forms the cutting edge forge laminated over a softer body which gives toughness.
The hollowed back as WB is said to be to ease flattening the very hard steel.
This in Japan the books say is traditionally done using carborundum grit on an accurately flat steel plate (a kanaban) - lapping until the grit breaks down to very fine particles and produces a finely polished and flat surface. Here's a random link to some information: https://covingtonandsons.com/2020/01/19/sharpening-part-20-flattening-and-polishing-the-ura/
There may (see below) despite the fact that many Western writers advise flattening backs on waterstones be good reason for this....
It's not recommended that laminated chisels are hollow ground on the bevel although some do it for convenience given their grinding set ups - that removes support from behind the cutting edge and is said to increase the risk of chipping out. They will chip if dropped on a concrete floor or used to open paint tins, but don't in my experience do so in hardwoods.
I've been grinding the paring chisels at 25 deg and the others at 30 deg.
I've evolved a sharpening (and re-sharpening) procedure which works well for me for both plane irons and chisels with thanks to others that have written on the subject. Waterstones on good steel were in my case a revelation - they cut fast but deliver a really sharp edge. Finishing to a fine grit I think is significant so far as durability of the edge is concerned.
My thanks go to David Charlesworth from back in the 90s for the original inspiration.
The real work with chisels is in flattening the backs, in forming the bevel and initial sharpening.
Re-sharpening as below takes only minutes.
After a few false starts I've ended up grinding on a WorkSharp fitted with a roughly 120 grit diamond lapidary disc (very cheap - but the grit chosen matters as too coarse will leave scratches which are hard to remove) - both for initial flattening of the backs (this with a lot of care) and to form the bevel. The latter using a Veritas honing guide to set the correct angle - with the Worksharp platform very carefully set so that it's in the same plane as the disc so that the angle setting is not lost upon transferring to the waterstones. It runs at low speed and so avoids the risk of overheating the steel - and produces the preferred flat bevel.
It's then a matter of working up through the grits to 12,000 on repeatedly flattened waterstones (using an Atoma 400 diamond plate for the flattening the waterstones under a tap) more or less as described years ago by David in F&C - and still using the honing guide in the case of the bevel. (without ever removing the chisel from it so that the angle is not altered) The back of course is finished before doing the bevel.
Waterstones hollow quickly so that repeated flattening is essential - even in the case of the Shaptons which reputedly are harder than most.
This with a light touch when finishing off and in the handling of wire edges delivers a very sharp edge.
A few strokes on a hard and smooth leather strop with green Veritas honing compound glued to a ply base finishes the edge off - only one or two in the flat on the back to avoid accidentally creating a bevel.
It's surprising how much effect the strop has..
I touch up frequently on the strop while working on the bevel side with only the tiniest wipe flat on the back for the above reason.
I'll hand re-sharpen via a quick rub each on the two finest waterstones after a few touch ups on the strop - taking great care to use finger pressure to hold the bevel of the chisel down to the front, again wiping on the strop to finish off.
Little and often seems to work best.
The hand re-sharpening in my case tends to produce a very slight rounding of the bevel which may even result in a longer lasting edge. Either way it's quickly removed after a few re-sharpenings by going back to the 1000 grit waterstone (or the 1200 diamond plate which cuts a bit faster when fresh but is of similar roughness) with the Veritas honing guide.
My original post was to communicate the discovery (it was news to me anyway - the issue only recently became obvious when paring large flat surfaces for the current bench project using a guide block) that flattening the chisel backs on a waterstone seems to produce a tiny bevel at the edge - possibly as a result of a wave of slurry building up under it. This doesn't seem to be produced by the strop - (a) because it's used in the flat for only a stroke or two, and (b) because chisels that had not been stropped performed the same.
This in retrospect may as above be why the traditional Japanese method of back flattening uses a lapping plate. I hope to tool up to try the method out when the bench project is out of the way.
Whatever the case a quick re-flattening of the backs on a 1200 Atoma diamond as described before carefully restoring the polish with a few strokes on each (carefully washed to remove the slurry) waterstone produced a noticeable change in the handling of the chisels when paring.
A PS because I forgot to mention the following.
A few strokes on the fine diamond also revealed that the suspected flat side micro bevel was actually a roughly parabolic hollow which extends from the corners back for maybe 3 or 4mm - it remained shiny from the waterstones because it was not initially reached by the very flat diamond plate. The same form of hollow was seen on three chisels one after the other.
A few more strokes on the plate caused the shiny patches to disappear so they were very shallow indeed - yet seemingly enough to as described above produce a noticeable effect when fine paring/paring off a guide block.
The haziness/marking on the polished backs and bevels of the chisels in the pics are by the way just smears of camelia oil

 

[Woodbloke]

My dad taught me to sharpen chisels and plane blades when I was around 7. We used an oil stone and some kind of thin oil in a dispenser with a flexible tube. Stropping was done on an ancient leather belt or maybe piece of harness that was some part of my grandfathers WWI army kit. Sharpening stuff, including shears and scythes, was routine, quite easy and no big deal was ever made of it. I still have those chisels, plane, oil stone and strop and still use them sometimes. Think I may even have the oiler as well. Every method works.

There was an interesting snippet on the CHT e-mail very recently were 'the Schwarz' explained his sharpening set up. He went to great pains to point out that none of it was donated to him and he paid full price for all the items (both questionable). However he did mention at length that there are loads of different ways to hone an edge and that they all work - Rob

My Personal Sharpening Kit - Lost Art Press

We are filming a full-length video to complement my “Sharpen This” book. Megan is filming it, and I am editing it. The video will be available next month.

blog.lostartpress.com

 

[AJB Temple]

Re the Japanese chisels and the ura, I honestly don't know how anyone wears them out. I've used, very often, a handmade set acquired in one of our trips and they will be 10 years old this November. I've sharpened the main users scores of times, and I guess it would take at least a hundred years to get even close to wearing any of them out. Not at the top of my worry list. The J steel sharpens fast and easily and usually just needs two swipes and a quick strop. I don't care about sharpening really: if I can get it to cut easily then that's fine for me.

 

[vaj]

I think to be fair that while the sought for outcome is very simple (the classic two finely finished faces meeting in the required location and at the required angle) and is not hard to maintain (via re-sharpening using a time and labour efficient method) that there's an awful lot of complexity, technique, subtle feeling and scope for messing up that sits behind it.
People get frustrated and/or hung up on differing options when the detail is explained - it gets tedious.
On the other hand the mythical grumpy old f*** that the frustrated like to refer to that says 'just give it a quick rub on this and a wipe on the a*** of your trousers' is selling himself short. (or setting the learner up to fail)
The ability to put a truly sharp edge on a tool as beginners demonstrate time and again is something that for most takes time and experience to develop. Even handed a viable working technique there's a gazillion unmentioned subtleties and opportunities by which all but the most sensitive will screw up...

 

[Phil Pascoe]

Most of the friction on posts in the other place is caused by one person and his inability to accept that there is more than one route to success.
I prefer water stones (and have for 40 years) but wouldn't dream of telling anyone that they are the only answer, that all their problems will solved if they use them. They work for me, and that's all that matters to me.

 

[TrimTheKing]

...They work for me, and that's all that matters to me...

And there we have the key to harmony!