Thread: Removing the convexed area ("belly") from a badly convexed chisel

Just a quick follow up on the issue that I thought would excite most, in terms of whether this method just gouges out an unattractive hollow right across the back of the chisel which (being right across the width) might interfere with actual work.

This is exactly the same chisel after about a minute lapping back and forth on the same DMT 300 grit stone:

Image 6.jpg

What you can see is that:

1. The hollow is almost entirely gone. Because there were repeated, light grinds that just attacked the high spots, the chisel now looks as it would after being lapped hard for hours on a flat stone. This method seems aggressive but does not create Franken-chisels. The hollow is temporary and removed in the final lapping process.

2. I am still a fairly long way from the tip. I actually stopped far too soon and need to re-establish that hollow because lapping is now hitting the the entire length of the chisel.

But at the risk of repetition, it is rapid - which with this task is not merely a matter of being lazy but making a virtually impossible task possible.

Just one final follow-up.

This was in my head and the geometry and line diagrams were running through my head during the day. I think I have figured out a (note "a", perhaps not the best) method of quickly lapping down to the tip without more faffing around and, again, with do-able effort (5-10 minutes, not an hour).

This is how I then lapped flat on the same, bog-standard, 300-grit diamond plate in about 5 minutes.

Essentially there are two movements - but a critical feature of these are they are *only done prior to you hitting the tip and not afterwards*

Movement 1 is hitting the front inch or so of the chisel only, back and forth. Now intuitively this is bad for flatness - it is hitting your flat with a bias. But a diagram I will post below explains why I think this is not merely appropriate but very effective up until the point you are almost lapped flat to the edge.

Lapping Movement 1.jpg

As I will attempt to put in a diagram, the purpose of this is to effective lower the angle of the plane which is abrading the face in "movement 2".

After about 20 strokes, check you are not hitting the tip you want to get to, then switch to "movement 2":

Lapping Movement 2.jpg

After an even number of strokes, switch back to movement one until you are a bee's whatsit from the tip. The very tip (0.5mm or so) will likely come off with sharpening anyway.

The result after not more than 5 minutes following this morning's 5-10 minutes (just on a 300 grit stone, no polishing yet):

Lapping Result.jpg

About a hair's width of pitted edge is left on which will come out in the sharpening.

I again emphasise, these movements should *not* be done from here on if you want a reasonably lengthy reference. I will try and do a diagram to explain in a follow-up.

Chris

And the attempted diagram for why I consider the final "movement 1" and "movement 2" provide a dramatic benefit when you are getting close to the tip but have slowed right down again because you have a substantial flat area developed (but not to the tip you want to reach).

Lapping diagram.png

In short, the objective of movement 1 is to remove material near to the tip, in order to modify what will happen during "movement 2" (ie, change the angle of the plane that is being abraded when the entire back is placed on the available width of the lapping plate).

By effectively abrading about an inch worth at the front, when you then switch to abrading the full width, one effectively changes the angle of attack upwards to sensibly actually remove the minimum necessary to get the whole functional area of the back into a plane.

This is also why you strictly need to stop this when you are just about to hit the tip. This is to correct and area and achieve a functionally large flat area near the tip only.

In theory you would create the risk of pivoting on a bump in the middle by movement 1. It is going to be tiny and almost impossible to actually pivot functionally before it is abraded away. At this stage I have not experienced it and the results were surprisingly quick and good.

Chris

this is sort of a variation of something I do when *making* chisels, though I only worry about a belly on older chisels if it's right at the tip of the chisel. If the last inch of the chisel is OK, there's not much to think about because the chisel's path is long ago set once 1" of it is into a cut. I think a long-experienced worker would prefer a chisel that's flat only at the business end and with a little relief the rest of the way up.

Charlesworth is obsessed with jigging and having sort of everything lined up and removing yourself from the equation. I haven't seen too many professionals work like that, but he's teaching beginners.

When the relief at the very edge is short and very steep, though, you can't get to the burr. If you can't get to the burr, you're definitely not going to polish the back side of the edge. Even the polish is a little overrated as to its value, but having a strong burr on the edge and having to tear it off is very detrimental.

(I learned to sharpen from charlesworth, but his methods that rely on a chisel being perfectly flat and with perfectly even sides were a little too much trouble to implement - very fiddly and slow and detrimental to developing further more productive skill if clung to for too long).

I don't disagree with what you've said about jigs. I firmly refuse to use jigs for sharpening and day-to-day maintenance. For chisels It's a hollow grind for me if angle is critical and a unicorn if not.

I have been persuaded, however, to being fussy about setting up chisels in one-time operations and broad corrections.

The project came about from frustration dovetailing in a recent project where I only had a single vintage chisel the right size for chopping out pins. For various reasons you can probably imagine, chasing the burr off an imperfect back was a fool's errand. I also became aware of slight depressions in the corners that weren't getting sharpened and frustrating all my efforts.

Chris

I should add: the reason I think it can often be valid to get fussy about establishing the back as a one-time task is if you have hard dubbing at the sides and into the corners close to the tip. Grinding this back isn't a solution if the belly persists further back in the chisel - one will simply reveal further depressed sides further back. This method is designed to destroy the belly as far back as 3" or so in a long chisel quickly.

(Couldn't say with confidence why so many bellies are on vintage chisels. I assume caused by repetitive hard stoning the tip and dubbing the sides, and perhaps workers just giving up on chisels once the problem has compounded to the point they can't sharpen. But this is speculation.)

Chris

Originally Posted by D.W.

this is sort of a variation of something I do when *making* chisels, though I only worry about a belly on older chisels if it's right at the tip of the chisel. If the last inch of the chisel is OK, there's not much to think about because the chisel's path is long ago set once 1" of it is into a cut. I think a long-experienced worker would prefer a chisel that's flat only at the business end and with a little relief the rest of the way up.

Charlesworth is obsessed with jigging and having sort of everything lined up and removing yourself from the equation. I haven't seen too many professionals work like that, but he's teaching beginners.

When the relief at the very edge is short and very steep, though, you can't get to the burr. If you can't get to the burr, you're definitely not going to polish the back side of the edge. Even the polish is a little overrated as to its value, but having a strong burr on the edge and having to tear it off is very detrimental.

(I learned to sharpen from charlesworth, but his methods that rely on a chisel being perfectly flat and with perfectly even sides were a little too much trouble to implement - very fiddly and slow and detrimental to developing further more productive skill if clung to for too long).

I think you'd find bellies on old tools because the craftsmen didn't mind them that way - but it's hard to say that if the tools aren't otherwise neatly kept. My preference in thought is an area the size of a thumb pad or two fingers, because that's what you can get pressure on and then bias toward the tip of a tool. that prevents a belly from forming more than what's there in the first place and always has you working the very tip.

but there's a lot of merit in what you say. I can tell you that x, y and z are unimportant for fine work, and then five beginners will come along with one thing wrong that *is* important that I wouldn't tolerate and then nobody knows if it's X, Y or Z.

if I get a new tool or new plane ,I still go over it no matter what, too - there's rarely a situation where the time spent isn't worthwhile in the long run

It doesn't matter of course (why all old tools one acquires all seem to be in bad shape) but it does pique my curiosity.

I think there is a real risk of assuming a "craftsman" class had owned all the tools being cleared out in estate sales. Presumably many homeowners of yester years either inherited or wound up with a pile of tools in their garden shed or under the house, or bought a couple as they needed for a task or project, had an oilstone or two and a little bit of experience from school or growing up but not in fine work because it didn't matter if they were just fixing up stuff around the house or building a tree house.

I recall reading a blog post by Christopher Schwarz speculating on why it is so many old chisels and planes had such bad backs given that fine work was being done. A possibility that seems likely to me is that cabinetmakers, furniture makers and other "craftsman" with tools kept in immaculate working order would (a) have had quite a few tools accumulated over their working lives and (b) known the value of them and therefore would have either sold the bulk of them when they retired or left them with friends and colleagues, instead of putting them in a bucket to rust under their house.

In other words, the buckets of rusty tools being dumped on second-hand markets are the ones not worth doing something about.

Originally Posted by D.W.

I think you'd find bellies on old tools because the craftsmen didn't mind them that way - but it's hard to say that if the tools aren't otherwise neatly kept. My preference in thought is an area the size of a thumb pad or two fingers, because that's what you can get pressure on and then bias toward the tip of a tool. that prevents a belly from forming more than what's there in the first place and always has you working the very tip.

but there's a lot of merit in what you say. I can tell you that x, y and z are unimportant for fine work, and then five beginners will come along with one thing wrong that *is* important that I wouldn't tolerate and then nobody knows if it's X, Y or Z.

if I get a new tool or new plane ,I still go over it no matter what, too - there's rarely a situation where the time spent isn't worthwhile in the long run

I remember Chris supposing things, as well as others. Larry Williams (who should know better) suggested that all of the "good" (single iron planes) made after the double iron plane was introduced were "used up" and thus no longer around.

That's a supposition that has no credibility, but it was repeated by others. The answer is far more likely to be that the double iron plane economically eliminated the single iron plane because it's literally better at everything (mitigating tearout, volume of work over time - probably the biggest improvement - increment of time between sharpenings and even in maintaining performance with moderate seasonal movement). The economic argument is something one comes to quickly if they're working wood from rough by hand (it's what drove me to try double iron planes - I believed a lot of what larry wrote and had a whole set of single iron planes "optimized" for dimensioning wood. It was still intolerable. My jointer was probably one of the last high quality single iron planes - made by a maker in the US around 1825 - and I lucked into it because someone had kept it dry and rust free for eons and it was being used as a doorstop. It probably resided in a barn or factory building above the ground floor - just pure luck).

So, back to the chisels - Chris's explanation can explain some, but not all. I've gotten little used chisels from england that were sharpened carefully, and none had evidence of the backs being carefully flattened. They did have evidence of being carefully honed (and to the chagrin of some, there was no consistency from one set to the next in how craftsmen chose to keep the primary bevel - some were like paul sellers describes - but not many - and far more had a very long thin primary bevel with a very steep secondary - a little more sloppy than I prefer, but they were also likely working mahogany which almost works itself.

To understand why the back flattening isn't that important, you can take a chisel that's got some belly and carefully work the last half inch to inch so that the burr can be removed and the edge polished, and then use the thing in actual work. Your brain will be completely indifferent to the back of the chisel - you're going to (as a matter of craftsman's sense) adjust to get the result you want. I have older chisels with boxwood handles that bent when drying, or with backs squirrely away from the edge, and I imagined the problems those things would cause, and then in the process of doing work (half blinds, trimming tenons, etc) all of that went away and I could see why nobody ever bothered to replace the handles.

It's a little harder for us in the states here to find old tools that weren't carefully kept because everything was pretty much site tools once industrialization occurred. The stanley 750 is a site tool, and the handles, I guess I don't know exactly why they chose short ones, but I don't do site work. The more interesting thing is that I can reharden a stanley 750 to hang with a V11 chisel (at least) in about five minutes, so stanley very deliberately made the tools softer than you'd find with older english cabinetmaking chisels.

I think a lot of times, you get someone like Chris who everyone wants to hear from. He feels obligated to give an answer or suppose something when he really should probably say "I don't know, maybe we don't know enough about the tools to know why some aren't flat"

(I'll check and see if I have any parers that I haven't flattened the last inch on - even they show up sharp, but the back is never really flattened totally and often bits of the edge aren't polished on the underside. I think if you get to work mahogany with parers, you can get away with that kind of stuff and the visualizing of preparing backs of chisels, etc, is sort of a modern thing.

...one vexed further by the fact that japanese chisels of high regard can be made with the back bellied on purpose so that you're only flattening the tip (some people prefer a back like that even though it's not enough belly to make the handles clear whatever is being cut. The relief under the back is nice to have to prevent a chisel from diving (I guess I"m saying and I'd state it definitively, with parers or bench chisels making a deep cut, you want a little of that relief or the chisel dives and you have no recourse. There are enough little used tools such that we'd find them if perfect back prep was ever well practiced, even if there are tons and tons of abused and discarded/ignored tools that weren't cared for).

On how the hollow (ura) was/is formed on Japanese chisels and plane blades...

Originally this was done prior to heat treatment with a draw knife called a sen. Other than on some high end blades it is no longer done in this time consuming way.

Nowadays specialised large diameter grinders are used. These are definitely not available in the Carbatec catalogue!

Japanese grinding wheel for Ura used by ishido6.jpg

I agree the 1/2" or so is all that matters in most cases. Indeed I doubt much flatness is needed once you are talking about difference in flatness revealed only by lapping at higher grits. 1 micron is 0.001mm. If anyone thinks their hands, eyes, hand pressure and how the wood will microscopically push the chisel off the back when chopping are going to be consistent with that type of flatness, I have a bridge to sell them.

The reason I flatten further and worked on the method outlined above is simply because once you have a tiny area (say 2mm or so at the tip) that is convexed, how do you physically access that and functionally flatten and polish that, and consistently lap so as to achieve a polish at the tip (the polish at the tip mattering).

Others may have super-fingers, but I can only keep a chisel flat on the stone with at least about an inch or so registered on the surface on a side by side action - and that is width wider chisels.

Thanks Neil I did see a video of that in action. As typical it seems the craftsman take 5 seconds in a bored fashion with 20 years practice and everything set up.

I would be interested in any practical ways to add a hollow other than faffing around with a Dremel.

I hope the whole point of the thread made clear that I am a believer in getting there quick so you can get back to your woodworking (ie, the method in this threat is about flattening *for the purpose of being able to lap and polish the tip* and not for the sake of a length of gleaming metal).

For me, I can't see why I wouldn't hollow if I could practicably.

Originally Posted by NeilS

On how the hollow (ura) was/is formed on Japanese chisels and plane blades...

Originally this was done prior to heat treatment with a draw knife called a sen. Other than on some high end blades it is no longer done in this time consuming way.

Nowadays specialised large diameter grinders are used. These are definitely not available in the Carbatec catalogue!

Japanese grinding wheel for Ura used by ishido6.jpg

and here is a video of a Jaoanese chisel maker putting a hollow in the backs:

Japanese Tool making Part 2 - YouTube ,.... at the 16'20" mark

A few thoughts:

• On old planes and chisels, maybe they all went into the pot for the war efforts
• Old chisels being bent? I'd reckon these were the "Bunnings" level chisels that are left over. Bought cheaply by the typical DIYer, used a few times, then left on a shelf to rust away quietly...
• On being bent two .... ever seen how a chisel is used by a non-woodworker? Its pure evil.
• WHY aren't western chisels made with hollow J-style packs? Seems odd. Much harder to finish off. Curious.

On flattening... I had a few old Stanleys like this. I turned the belt sander upside down, put on a 60 grit belt, and BLASTED it. It was flat in no time

CGCC, why didn't you use the side of that CBN wheel for the job?