flattening chisel backs with lapping film

[J_SAMa]

I've never needed to flatten chisel backs. All my chisels came flat or concave. A little concave is OK right? :? I mean look at them Japanese chisels.

 

[Jacob]

I've never needed to flatten chisel backs. All my chisels came flat or concave. A little concave is OK right? :? I mean look at them Japanese chisels.

Sure it is. And a little convex doesn't matter much either (depending on what you are doing!)
And flattening plane blade faces is madness. The only bit which counts is the 2 or 3mm behind the edge where the cap iron needs to fit tight.

 

[Corneel]

I confess, I am a back lapper. Almost all my tools are old, and the back is usually slightly pitted and very convex. It's always difficult to reach the corners and the very edge. So allthough I agree only the last 2-3mm are important, it's not easy to actually reach them. I want to have all my irons in use the same kind of flattness, not one iron needing a backbevel, the other not etc. And only lapping a very short line doesn't really work because the iron is so unstable on the stone.

So, I lap backs. Whenever I buy a "new" old tool, I also buy a lot of work. I flatten about 3/4 to a full inch. It is indeed a lot of work, but it buys me peace of mind and easy sharpening for the rest of the lifetime of that tool. I get the fastest results now with a Sigma 120 stone, and 400, 1000, 4000 and 8000 stones after that.

That said, with a new expensive chisel I wouldn't accept this convexity and send them back.

 

[Peter Sefton]

We lap new chisels on Glass and Scary sharp to remove grinding marks and improve flatness if required, when students bring in old chisels we give them the same treatment but this is usually to remove the rounding that has been self-inflicted by sharpening on old rounded oils stones or water stones that have not been flattened on a regular basis.

 

[David C]

At last some sanity! Chisel backs have been worked on by cabinetmakers, for hundreds of years.

Japanese chisels are the same, not ready for use.

As Bugbear said, manufacturers grinding marks need to be polished out in the vicinity of the edge.

best wishes,
David Charlesworth

 

[Jacob]

So what would you say to Madge (the OP)?
Personally I think he's wasting his time. An hour on one chisel and still not right!
It's probably too late but my advice would have been to sharpen them a few times and use them, and they'd improve as any imperfections disappear (if there are any).

 

[Noel]

I used to lap away at the back of chisels some years ago. Why? Because, apparently it was the done thing. The comics said it was the only way to have a fully functioning tool, it was mentioned on all the WW forums too. You weren't a proper woodworker unless you flattened the backs of your chisels....Who was I to disagree....
Then I got lazy, skipped the boring part, sharpened the tool and used it. Hey, perhaps my standards are low, but I was happy and saw no noticeable difference in performance. The chisel was sharp, it did the job and held a decent edge, that was all I wanted. Ok, some car boot items were banana shaped but they were left to another day when a total regrind was needed.

Blade preparation holds much in common with the game of golf where some folk spend endless hours trying to prefect a particular aspect of the swing. They would be much happier just thinking- see ball, hit ball. Simple.

Interesting blog (apart from the odd spelling mistake):

How the flat back craze started I’m not sure. I will admit that I subscribed to the flat back camp at one time. That is, until I started buying old tools. After spending a rediculous amount of time trying to flatten a few of the antique chisels and plane irons I had acquired, I began to think that there had to be a better way. There was no way that our ancestors would have spent so much time on such a task that had no financial value to them at all. They needed to get their tools sharp and get back to work. Let’s face it, flattening chisel backs does not put food on the table.

http://logancabinetshoppe.com/blog/2011 ... p-lapping/

 

[Jacob]

I believed it too some time back. Not that I ever did it but I felt I was a bit of a slacker and might get caught out if a "fine woodworker" happened to drop in!
Doesn't matter much, but I ebayed some very nice but slightly un-flat chisels on the assumption that they were somehow no good. With hindsight, a mistake. One of them was a "J Fowler St John New Brunswick" 1" socket bevel edge, which was probably the best chisel ever to pass through my clumsy hands!

PS Excellent link!

 

[Corneel]

Interesting article from Bob from the Logan cabinet shop but it doesn't quite adres my trouble with sharpening old chisels and plane blades with pitted and 3 dimensional convex backs. Especialy the corners tend to drop down, and I really like sharp corners in a chisel. And sorry, but I don't spend more then an hour per chisel. Just some work once, saves me time everytime in the future when I sharpen the blade, because I don't need to search for the edge.

I guess it's just a matter of personal preference.

 

[Jacob]

Yes some old ones need metalwork doing on them no doubt, but I think many don't, and our OP was misinformed about what he should do.

 

[Corneel]

Indeed new chisels shouldn't need so much work. A bit of work on the stones to polish them up. No extensive backlapping.

 

[Noel]

Indeed new chisels shouldn't need so much work. A bit of work on the stones to polish them up. No extensive backlapping.

Exactly, but everywhere you turn to learn about sharpening, it's "get the backs mirror flat" etc, etc.
Sharpen them, take off the wire and they'll be nice and shiny in no time.

Like here: http://www.youtube.com/watch?v=9aDPZzMvVTA

I guess some folk have to make a living...

 

[GazPal]

Indeed new chisels shouldn't need so much work. A bit of work on the stones to polish them up. No extensive backlapping.

Exactly, but everywhere you turn to learn about sharpening, it's "get the backs mirror flat" etc, etc.
Sharpen them, take off the wire and they'll be nice and shiny in no time.

Like here: http://www.youtube.com/watch?v=9aDPZzMvVTA

I guess some folk have to make a living...

This plus 50,000,000 Sharpening and edge maintenance need to be high among your priorities and directly alongside learning how best to use tools. Too much focus on tool fettling detracts from the how and when to use certain tools and - in spite of what's often said - the best way to achieve the well worn and polished look with built in patina is by putting a toolkit to good use and trying not to altar worship it or it's makers. I often feel far too much emphasis is placed on treating tools as though they're not intended for use in their primary roles.

 

[Jacob]

Indeed new chisels shouldn't need so much work. A bit of work on the stones to polish them up. No extensive backlapping.

Exactly, but everywhere you turn to learn about sharpening, it's "get the backs mirror flat" etc, etc.
Sharpen them, take off the wire and they'll be nice and shiny in no time.

Like here: http://www.youtube.com/watch?v=9aDPZzMvVTA

I guess some folk have to make a living...

What's interesting about that video is that the first thing he says is obviously wrong, so it follows that everything else is doubtful.
The first thing he says is that the face of a chisel functions the same as the sole of a plane as "the reference surface" etc. It's not as simple as 'untrue' it's just meaningless. They are very different tools used in very different ways.
Try cutting a mortice with a plane.
What about "try flattening a surface with a chisel"? Possible, but you'd have to do it bevel down.
I like his funny honing dance, though I wouldn't recommend it! :lol:

 

[Kalimna]

Jacob - is it not the case that when paring, the flat face of the chisel is indeed used as a reference surface to allow accurate paring? I think the chappie mentions this in the video. Cutting a mortice is a slightly different task again, is it not?

Cheers,
Adam

 

[Jacob]

Jacob - is it not the case that when paring, the flat face of the chisel is indeed used as a reference surface to allow accurate paring? I think the chappie mentions this in the video. ....

Cheers,
Adam

I can see the attraction of the idea, it sounds rational, but in reality it's just not like that is it?

And the idea that flattening is an old and respectable tradition - the most common observation made about recently acquired old tools is that they are not flat or polished! Clearly nobody bothered that much.
I've just bought 20 old wooden planes, most of them obviously very well used. Absolutely no sign of efforts to flatten or polish faces, beyond the usual requirements of sharpening. And the nearly all have rounded bevels! How on earth did these old woodworkers manage? Clearly they knew little about tool preparation and sharpening!

 

[David C]

Jacob's breathtaking and obtuse refusal to understand traditional methods, is a wonder to behold.

David Charlesworth

 

[Jacob]

Jacob's breathtaking and obtuse refusal to understand traditional methods, is a wonder to behold.

David Charlesworth

And all those old woodworkers too - obviously they didn't know how to do it either! :lol:
If only someone had been around to explain things to them!

Actually I've been into trad woodwork for most of my life, Hands on, eyes open, mainly conservation work in old buildings, 'architectural' joinery - repairing and replicating sash windows, panelled doors, plus a few excursion into furniture and other aspects of woodwork.
I've taken more particular interest in hand tools in the last few years, which means a lot of time separating myth from reality!
My sharpening improved enormously as soon as I dumped the jigs.

 

[Cheshirechappie]

I had intended not to post on this thread, since it seems to be descending into something of an unseemly brawl, but I can't help feeling there are a couple of important points not yet raised.

Firstly, how a chisel is prepared and sharpened depends on the duties expected of it. Secondly, the sharpness of an edge is dictated by the smoothness of two intersecting faces; a chisel can only be as sharp as the rougher of the two faces.

For very rough carpentry, when the chisel will be used with a large mallet or hammer to remove a lot of waste wood quickly and without the need for a precision finish, almost anything with a sharpish edge and a bit of 'beef' in it's design will do. Hence double-hooped handles, thick registered blades and similar features. Edges straight from a grinder will sometimes do, or just tickled up on a medium oilstone. The flat face needs to be flattish, but polishing it won't add to performance.

For most joinery, something a bit better is needed, but as most work is chopping rather than paring, razor-sharp edges won't last long. Chisel flat faces need to fairly flat and preferably free of grinder scratches, but high polish won't add significantly to performance.

For fine cabinetmaking and finish woodcarving, when joints that may be a visual design feature of the work so must fit closely, and when it may be impossible to refine the surface after chisel work (as in much carving) a very sharp edge is needed, combined with a capacity to work to quite fine levels of precision. In this case, flat faces that are genuinely flat do have a role to play, and to achieve the highest sharpness the steel is capable of needs careful work to polish both intersecting edge faces. The polish only needs to be a fraction of an inch behind the edge on both flat face and bevel face, but for convenience it often extends further on the flat face - just polishing the edge is very difficult to do without compromising the flatness of the face.

I can't find the reference now, but someone recently posted about plane makers and the chisels they used to pare the iron beds of wooden planes. When their paring chisels started to get short from being sharpened over a period of years, they started the long process of flattening and polishing the flat face of a new chisel. They started this some months before they needed to use it, because the process took so long with the equipment they then had (and because if you're on piece-work, you do such jobs in your lunch-hour, so have to spread it out.) Chisel flattening is not new by any means.

Most workers (except perhaps carvers) probably only need the 'ultimate' chisels occasionally, so maybe it's best to have a small set of really highly prepared flat-faced, ultra-sharp chisels kept for fine fitting and end-grain paring, and a set of 'normal work' chisels used for the bulk of chopping and wood-shifting duties. A set of firmers supported by a few fine paring chisels, if you like. You don't need to have every chisel you own polished to optical flatness, just a few 'special' ones flat on the back and polished close to the edge.

 

[Jacob]

I'd agree with that in general. What you are saying (IMHO!) is horses for courses. And yes for very specialised things like plane making some nice straight chisels will help! I did one myself recently (new sole on old plane) with an axi cheapy. Nice and flat, holds an edge well. And for precision sharpness is necessary.
But I'm dubious about long process of flattening, months ahead, etc. Sounds a bit like tales of the old woodworker! More sensible to start with a flat chisel if you need one desperately, and as and when, rather than preparing months ahead. Or to use a chisel in the ordinary way but take care of it so that in months ahead it is looking good, flat and polished
But to get back to madge (OP) - she's wasting her time and not doing her chisels any good. Just sharpen them madge and get on with some woodwork!
BTW where was/is the unseemly brawl I seem to have missed it?

PS interestingly - carvers, who use chisels more often and more precisely than anybody else as a rule, go for polished double bevels, slightly rounded.

The best way to flatten and polish tools is to use them a lot.