# flattening the back of a chisel



## matjos26 (1 Dec 2013)

How important is it to flatten the back of a new chisel ive been watching a few you tube videos and allot of them put allot of time in to this more than the beveled angle itself


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## Kalimna (1 Dec 2013)

I think that the general consensus on here is that, unless you are doing the finest of cabinetry, that absolute flatness is not necessary.
Removal of machining marks will ensure an edge of the finest nature, but it's probably unlikely that you would notice. 
An exception to this might be use of a paring chisel, where you may want a greater degree of flatness to improve the 'self jigging' effect.

You will also find that several polar opinions are likely to be offered. Try and read between the lines and analyse the advice. If it makes sense, then follow it. If not, then don't.

Cheers.
Adam


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## tobytools (1 Dec 2013)

As stated it depend what you want to use your chisel for, if it to open a tin of pair then a bend wouldn't matter. For a carving chisel not a problem, for a paring chisel a bigger problem.
At the end if the day there isn't a right or wrong, this sort of question falls behind the "sharpening" debate.
That being said it's better to have a true chisel in my eyes.

Japanese chisels have a hollow/belly on there backs. 

TT


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## Jacob (1 Dec 2013)

It's a completely pointless waste of time in my opinion.

Honing and turning to remove the burr will leave you with a polished area behind the edge without you having to do anything special.
Removing the slight concavity found with most new chisels will just make subsequent sharpenings slightly more difficult.
It takes 20 seconds or so to get a new chisel working.


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## AndyT (1 Dec 2013)

The forum software automatically searches for similar posts. If you want to see how this question has been answered before, look down the page at the links, especially the first one,if you have time to spare. 

https://www.ukworkshop.co.uk/forums/topic68506.html


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## Corneel (1 Dec 2013)

A NEW chisel shouldn't require any special attention. Polish it up a bit. If it happens to have a belly, so you can't reach the edge: send it back.

OLD chisels are another matter. You'll have to remove the pitting, because it interfere's with the edge. If it is severely bellied like a lot of them are, the you'd better only pay attention to the last 1/2" or so. Too much bother to adress that belly. And the chisel will cut nonetheless. If the belly is slight you might want to try to remove it first on very coarse sandpaper on a flat surface, but it is a lot of work.


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## bugbear (1 Dec 2013)

matjos26":11bu3v08 said:


> How important is it to flatten the back of a new chisel ive been watching a few you tube videos and allot of them put allot of time in to this more than the beveled angle itself



That's because the back is much larger than the bevel.

But it only needs doing once in the lifetime of a chisel. Back flattening isn't sharpening, it's "prep" or "fettling"

BugBear


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## RossJarvis (1 Dec 2013)

matjos26":2l7b09vv said:


> How important is it to flatten the back of a new chisel ive been watching a few you tube videos and allot of them put allot of time in to this more than the beveled angle itself



I have a set of Bahco chisels I've had for five years, every time I sharpen the chisels I spend some time trying to flatten the backs, I believe some of the thinner ones might have flat backs by now, the 36mm which I use most, after 5 years, is approaching having a flat back nearly up to the cutting edge. Generally they're fairly sharp in use, I'll tell you if they're any better with flat backs, but it could take another 5 years!


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## Scouse (1 Dec 2013)

If you have spent a few happy minutes on the forum, you will have gathered by now that there is more than one way to skin a cat when it comes to sharpening...

I flatten the backs of new chisels. I look at it like this; I'm going to spend the next however many years sharpening the tool, so I like to start from a known baseline on one of the two surfaces which will intersect to form a sharp edge. I'm not saying I'm right and everyone else is wrong, indeed I might be wrong, and wasting my time. It's my time, I don't mind. 

In the past few weeks I have bought 5 Ashley Iles dovetail chisels (Workshop Heaven, great service, great chisels), 3 Narex mortise chisels (Classic Handtools, great service, great chisels) and a couple of sets of Aldi bevel edge chisels (again, great chisels...).

They would probably have all been fine straight out of the box, but I wouldn't regard any new tool to be ready to use immediately, and as I said I like to check. No harm, no foul.

None of them required more than a couple of swipes on 800 and a couple on 4000, a minute or two per chisel, and all were very slightly hollow, which was nice.

I'm not sure if it is a new fad, I was tought to check new blades twenty-five years ago; anyhow it is a one time only operation, removing the wire burr after sharpening the bevel each time keeps them flat.

It does no harm, and it's a nice hour or two dodging 'Professional Masterchef'. 

But if you don't want to flatten, that's ok too.


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## David C (1 Dec 2013)

Convexity or concavity ?

I know which one is preferable.

David


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## G S Haydon (2 Dec 2013)

I would personally not flatten the whole back. I would work the back on you chosen medium until you have a 1/4" of honed metal behind the bevel. Other options are available.


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## Jason (2 Dec 2013)

Flat backs are probably no great advantage for chopping. But an advantage for pairing.

I suppose I'd inspect the back and see how much work I was looking at. If it's not going to be arduous and it's a chisel that'd be good for pairing then I'd go the extra distance. Otherwise, I might think better of it and do what's needed to get it chopping quickly or think better of it and spend my time elsewhere.

Haydon's suggestion will get you chopping and cutting quickly. But the down side is that you start giving your chisel an upturned nose - which is where it starts going wrong if you want the chisel to be good at pairing (though you'd still be fine for chamfers and some other things) - so I think it's worth taking a moment before you commit.


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## Jacob (3 Dec 2013)

Jason":80btmzfk said:


> ....
> Haydon's suggestion will get you chopping and cutting quickly. But the down side is that you start giving your chisel an upturned nose - which is where it starts going wrong if you want the chisel to be good at pairing .....


Well yes possibly, but in fact the slight upturn you find on most well used chisels (which haven't been repeatedly flattened) doesn't make any difference - or if it does you just use it slightly differently, probably without even being aware of it.
I feel that the general anxiety about "flatness" (bellied! :shock: ) is exaggerated and if your attention isn't drawn to it in practice you wouldn't notice it.
I'm slightly irritated by the flatness panic in that some years ago I sold on some perfectly OK chisels in the mistaken belief that they were unusable unless given hours of flattening attention. Just another woodworking myth.
I'm also puzzled by the notion that chisels need "prepping" any more than saws, screwdrivers, hammers etc. It's just another myth. People launch these redundant ideas and they float around, getting in everybodys way, unsinkable, for years!


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## G S Haydon (3 Dec 2013)

Hi Jason that is a valid point, mainly down to my poor explanation :lol:. I will put my money where my mouth is on this when I do a video review on the Narex chisels and bring some clarity to my point. 
From the OP's point of view and for any one looking for advice on the subject you will find collision with this issue very quickly

http://www.youtube.com/watch?v=9Wl_uQOABxg (I include myself within the group discussed in the video)

The key thing is finding a system that works for the type of work you do.


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## Scouse (3 Dec 2013)

Jacob":36jwg3uh said:


> I'm slightly irritated by the flatness panic in that some years ago I sold on some perfectly OK chisels in the mistaken belief that they were unusable unless given hours of flattening attention. Just another woodworking myth.



I wonder if there is a discrepancy between an idea of flattening the backs to an engineering tolerance and 90 seconds on a couple of stones to provide a corresponding polished surface to the bevel? I've not come across a chisel which needs hours of attention myself, but...



Jacob":36jwg3uh said:


> I'm also puzzled by the notion that chisels need "prepping" any more than saws, screwdrivers, hammers etc. It's just another myth. People launch these redundant ideas and they float around, getting in everybodys way, unsinkable, for years!



I thought you were a Sellers groupie? They're all at it :lol: 

http://www.youtube.com/watch?v=Ki8tt-VjwqI


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## Jacob (3 Dec 2013)

Scouse":1jmbvyxp said:


> ......
> I thought you were a Sellers groupie? ....


Not at all. I like most of what he says but nobody is perfect!

We had flattening ad nauseum back here post759803.html

To save you the bother I've copied and pasted my contribution here. Wouldn't change a word, except I'd add that you don't have to remove machine marks to reduce friction.

_Here's jh's chisel before and after. Old stock but unsharpened and with a cap to keep it in good nick. Ground at 25º























Distinctly concave along the length and slightly across the face so a paring cut will dive in a bit. It's not sharp so the result is more of a scrape






The kit; 2 oil stones and one strop;






The pink stone and 15 seconds later it's sharpish and machine marks almost gone (from the edge). Rounded bevel started so it's caught at the heel as well as the edge. Eventually after many sharpenings the whole bevel will be rounded with an edge at 30º;







The face near the edge is flattening out and shows up;






Another 30 seconds on beige stone and strop and it is sharp with machine marks gone (from the edge);











A planing/paring cut will pass over the surface without diving, unless you press it down near the edge and it will take off fine parings;






That's it. Say one minute in all, not counting getting the kit out and cleaning up. If you wanted it extremely sharp another 30 secs on a finer stone would do it. As the rounded bevel extends it will take a bit longer to hone which means spending longer on the coarser stones to back off the bevel.

It's self flattening - every time it is honed the flat area gets extended a touch and there's certainly no need to deliberately flatten or polish

Perfectly good chisel, well worth £1 + postage! Thanks jh._


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## Cheshirechappie (3 Dec 2013)

Jacob - I'm terribly sorry to be the one who has to break this news to you, but - what you've just done with that chisel is EXACTLY what the rest of us advocate when we talk about 'flattening the back of a new chisel'. We DON'T mean obtaining optical flatness and a deep chrome-like polish across the entire width and length back to the shoulder. We DO mean taking out the grinding marks just behind the cutting edge - just as you've done to that green-handled chisel!

Jacob - I'm so sorry. This probably means we now have much less to argue about....though no doubt you'll find something.


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## Jacob (3 Dec 2013)

Brilliant! Glad to hear it. :lol: 
But there is no "flattening" involved - just normal honing and turning to remove the burr. No "prepping" (stupid word); just sharpening. No removing of machine marks (except incidentally).

"Obtaining optical flatness" seems to have been the objective in earlier posts and people have talked of hours of work involved, working their way through grits etc. etc. and (see matjos26's OP) there are videos! (I name no names :roll: ).

OK so what do you want to argue about next?


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## Corneel (3 Dec 2013)

So, the new chisels are clear.

Now the old ones. I have a very nice old chisel here, Nooitgedagt, late 19th century, laminated blade, 4 cm wide. I've got some work to the back allready, but the left edge in this picture is still pitted and just a tad lower then the rest. In this condition I can't get the corner sharp. So either I leave it as is and don't use that corner, or I put more work into it.


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## Jacob (3 Dec 2013)

Depends what you want to do with it and whether or not you have an alternative.
Personally I'd leave it as it is (but aim to correct it over time with each sharpening) and use another chisel if I wanted one sharp right to the edge


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## Corneel (3 Dec 2013)

Actually I think about selling it. So I can leave it to the new owner or put in the extra work and raise a little bit extra money.


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## Jacob (3 Dec 2013)

Corneel":3m3ia97u said:


> Actually I think about selling it. So I can leave it to the new owner or put in the extra work and raise a little bit extra money.


Yes it's had it really. Looks like over enthusiastic buffing by the previous owner.


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## G S Haydon (3 Dec 2013)

Ok corneel, this is most likely a stupid idea so forgive me in advance but could you hollow out the back with a powered grinding medium so when you to try to create a flat back it focuses your work behind the edge? Like I said probably silly.


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## RossJarvis (3 Dec 2013)

G S Haydon":3e2dbiu9 said:


> Ok corneel, this is most likely a stupid idea so forgive me in advance but could you hollow out the back with a powered grinding medium so when you to try to create a flat back it focuses your work behind the edge? Like I said probably silly.



Not really a silly idea, as this is what Japanese Chisels have. Having given it a half hearted attempt myself, I think a reasonable amount of skill/experience is needed though. An engineers scraper may do the job, but it all comes back to time. My Bahco chisels (mainly designed for site use I think) all had convex backs so flattening these would be a bit of a nightmare, I've spent many a happy hour trying to get these right and I think I've just succeeded with the 36mm one, shame they're not particularly good as chisels


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## Corneel (3 Dec 2013)

I've done that in the past too. Using the round part of the bandsander where it goes over the roller, and making sure the edge never touches the sanding band. It is hard to control though.


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## Jason (3 Dec 2013)

Jacob":29r58hyb said:


> But there is no "flattening" involved...



In my experience, Marples chisels are almost always "flat" out the box.


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## MMUK (3 Dec 2013)

FWIW in my experience, albeit limited compared to others here, I have found that as long as the back is smooth and not obviously banana shaped then it works fine. I've not come across a chisel yet that has an obviously concave or convex back when looked at end on.


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## Jacob (3 Dec 2013)

Same here. Though on that green one above you could see the concavity. Not a problem.
The biggest prob is getting one like Corneel's above, which has had the edges rounded by an over enthusiastic polisher. Basically unusable - straight back on ebay with it!
Or reduce the width I suppose. Easier than flattening and might remove less metal?


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## Corneel (3 Dec 2013)

Jacob, it's also possible these kinds of chisels were produced on a hollow oilstone. If he would have sold his stone with this chisel, I might not have the same problem. Trouble is the convexness in combination with a bit of rust damage.

Personally I prefer flat(tish) stones.


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## Richard T (4 Dec 2013)

That's right Corneel, the tell - tale sign of the burr being taken off many times on a dished stone. It is (one of) the curses of buying old, used edge tools and the reason I splashed out big money on a extra coarse, dead flat diamond plate. Still a lot of work to get a straight line even just between the corners though ... something for the long, winter evenings. 

As you say, further work on a hollowed stone would get into the corners but (personally) I would not be satisfied with walking such an edge along a nice, straight scribed line for instance. Picky, maybe, but I like to start with the best tool I can.


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## Graham Orm (4 Dec 2013)

I'm neither pro or against hollow chisels, but please clarify this for me. If you're an enthusiastic sharpener and over use the grinder to take the primary bevel back, do you not eventually reach the hollow and end up with a concave tip to the chisel?


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## bugbear (4 Dec 2013)

Grayorm":191bvjd9 said:


> I'm neither pro or against hollow chisels, but please clarify this for me. If you're an enthusiastic sharpener and over use the grinder to take the primary bevel back, do you not eventually reach the hollow and end up with a concave tip to the chisel?



If you're talking about the Japanese model, it's "complicated". The hollow is shallow, and as the chisel wears, the hollow is actually FILLED IN (!!!!) by gentle, careful, accurate hammering on the upper side. This is only possible because the chisel is a thin hard layer laminated over a malleable support layer. But it's easy to get the hammering wrong.

So the hollowing, the hammering and the lamination are all part of an integrated process. You can't just pick one element (the hollowing) out and use it in isolation.

BugBear


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## Graham Orm (4 Dec 2013)

bugbear":2ms88ic6 said:


> Grayorm":2ms88ic6 said:
> 
> 
> > I'm neither pro or against hollow chisels, but please clarify this for me. If you're an enthusiastic sharpener and over use the grinder to take the primary bevel back, do you not eventually reach the hollow and end up with a concave tip to the chisel?
> ...



You have to hammer the chisel into a new shape????? That couldn't possibly be done accurately or without heating.


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## bugbear (4 Dec 2013)

Grayorm":yv7dvez0 said:


> You have to hammer the chisel into a new shape????? That couldn't possibly be done accurately or without heating.



Yes it can!

http://kskdesign.com.au/blog/files/tapp ... dashi.html

BugBear


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## Jacob (4 Dec 2013)

Grayorm":23qlxixb said:


> I'm neither pro or against hollow chisels, but please clarify this for me. If you're an enthusiastic sharpener and over use the grinder to take the primary bevel back, do you not eventually reach the hollow and end up with a concave tip to the chisel?


Every time you turn the face to take off the burr you flatten it slightly so the flat rim of the hollow gets moved back a touch as the hollow gets shallower.
So you'd expect the end of this chisel to look much the same even years later when it's lost an inch or so in length


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## Graham Orm (4 Dec 2013)

Jacob":3vw83b3t said:


> Grayorm":3vw83b3t said:
> 
> 
> > I'm neither pro or against hollow chisels, but please clarify this for me. If you're an enthusiastic sharpener and over use the grinder to take the primary bevel back, do you not eventually reach the hollow and end up with a concave tip to the chisel?
> ...



I'm struggling to get my head round it Jacob. Surely if it's concave when you grind back that 5mm or whatever there's a dip in the edge to conform with the hollow?


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## Graham Orm (4 Dec 2013)

bugbear":1o2gxf45 said:


> Grayorm":1o2gxf45 said:
> 
> 
> > You have to hammer the chisel into a new shape????? That couldn't possibly be done accurately or without heating.
> ...



I will take your word for it BB, sounds odd and not something I've ever seen or heard of. :wink:


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## Phil Pascoe (4 Dec 2013)

Grayorm":yjahr4cu said:


> Jacob":yjahr4cu said:
> 
> 
> > Grayorm":yjahr4cu said:
> ...


No, because the back gets flattened further back as you sharpen - just like Japanese ones.


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## Corneel (4 Dec 2013)

Tapping only for Japanese planeblades! Not chisels! You risc breaking your Japanese chisel. Just polish the back after each sharpening and the hollow will move back a bit each time.


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## bugbear (4 Dec 2013)

Grayorm":tml3g592 said:


> bugbear":tml3g592 said:
> 
> 
> > Grayorm":tml3g592 said:
> ...



That's the joy of other people, and the internet. You can learn new stuff! (did you follow the link?)

Corneel is right about it being plane blades only though.

BugBear


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## Jacob (4 Dec 2013)

Grayorm":gf8otek7 said:


> ....
> I'm struggling to get my head round it Jacob. Surely if it's concave when you grind back that 5mm or whatever there's a dip in the edge to conform with the hollow?


You take the edge back a bit which will narrow the flat rim, but then you take it _down_ a bit which will widen it i.e. if you flattened it completely the hollow would gradually shrink until it disappeared.


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## Cheshirechappie (4 Dec 2013)

There's a British Standard for woodworking chisels - http://shop.bsigroup.com/en/ProductDeta ... 0000192892 - so if anybody would like to shell out £100 for a sixteen-page document, we can find out what the official requirements are for chisel back flatness.


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## Billy Flitch (4 Dec 2013)

The question is do the makers of chisels in China Know about BS for wood working chisels or actually give a hoot.


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## Cheshirechappie (4 Dec 2013)

Billy Flitch":1378ynrz said:


> The question is do the makers of chisels in China Know about BS for wood working chisels or actually give a hoot.



Probably yes they know there's a BS, but no they don't give a hoot. It's not illegal to sell something that doesn't comply with a BS provided you don't claim that it does.


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## Graham Orm (4 Dec 2013)

phil.p":6ncfeibl said:


> Grayorm":6ncfeibl said:
> 
> 
> > Jacob":6ncfeibl said:
> ...



Spooky


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## Graham Orm (4 Dec 2013)

bugbear":yxqdw6rd said:


> Grayorm":yxqdw6rd said:
> 
> 
> > bugbear":yxqdw6rd said:
> ...



Even spookier!


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## David C (4 Dec 2013)

I would strongly advise against "tapping out" the hollow of a Japanese chisel.

Yes it can be done and yes it is done by some (very skilled people).

I tried once and knocked a large chip out of the edge of a favorite chisel.

With ten minutes work on the flat side, with the force just at the heel of the bevel, on a coarse 800g stone, I can "move the hollow back" by about 3mm. 

This is a much safer method.

Best wishes,
David Charlesworth


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## Vann (4 Dec 2013)

Is that actually a slight hollow on the back (face) of that chisel? Or is that the result of honing a flat chisel on a dished stone...?

Cheers, Vann.


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## Jacob (4 Dec 2013)

Hollow. Most new chisels are like this. Flattening them is a mistake, same as flattening one of those hollow faced jap chisels. It makes sharpening easier.


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## David C (4 Dec 2013)

Tapping out or moving the hollow back, is only done when repeated sharpenings have brought the edge to the edge of the hollow.

Nothing to do with removing the hollow or flattening the back.

David


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## RossJarvis (4 Dec 2013)

Jacob":202epqbt said:


> Hollow. Most new chisels are like this. Flattening them is a mistake, same as flattening one of those hollow faced jap chisels. It makes sharpening easier.



When I've heard of flattening the back of a chisel, Ive always assumed it's either flattening a convex backed chisel so that the cutting edge is in the same plane as the rest of the "face"/back/flat bit, or making sure the cutting edge and periphery are on the same plane. For any "hollow", unless it's on the cutting edge, you'd just leave it. Surely no-one would flatten the back of a chisel (particularly a Japanese one) to get rid of the hollow?

My Bahcos look flat but are slightly convex (only noticeable when lapped or checked with a straight edge) or up-angled, at least at the cutting edge, so the only way to get a good sharp edge is to flatten the back or hone the "face"/back/flat bit at a slightly raised angle (one degree-ish). For chopping this isn't a problem, but for paring it's not brilliant. Admittedly they're not particularly good chisels and really designed for bashing stuff on site and not bench work.


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## Jacob (5 Dec 2013)

RossJarvis":3krt1dts said:


> Jacob":3krt1dts said:
> 
> 
> > Hollow. Most new chisels are like this. Flattening them is a mistake, same as flattening one of those hollow faced jap chisels. It makes sharpening easier.
> ...


They do exactly that. There are dozens of threads about "prepping" (stupid word) chisels, which can involve hours of work, and videos. "Lapping" is the other stupid word!


> My Bahcos look flat but are slightly convex (only noticeable when lapped or checked with a straight edge) or up-angled, at least at the cutting edge, so the only way to get a good sharp edge is to flatten the back or hone the "face"/back/flat bit at a slightly raised angle (one degree-ish). ......


They all end up like that unless you flatten the whole face every time you sharpen. I can't quite see why it should be a problem, even for paring. Perhaps pattern makers need the flatness, I wouldn't know.
If you flattened every time you sharpened chisels wouldn't last very long.

Maybe it's all this chap's fault - http://www.youtube.com/watch?v=cOvkNuwO_YM he talks a lot of nonsense very convincingly.


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## bugbear (5 Dec 2013)

Jacob said:


> [There are dozens of threads about "prepping" (stupid word) chisels, which can involve hours of work, and videos. "Lapping" is the other stupid word!
> 
> 
> > Would you care to justify calling "prepping" and "lapping" stupid? They're perfectly good terms for the process being described. Calling them "stupid" seems needlessly perjorative.
> ...


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## Jacob (5 Dec 2013)

Because whenever I see the words "lapping" or "prepping" in these forums, it seems to entail some innocent beginner having been gulled into doing something fiddling, painstaking, difficult, but generally unnecessary.


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## bugbear (5 Dec 2013)

Jacob":1p4zzqh1 said:


> Because whenever I see the words "lapping" or "prepping" in these forums, it seems to entail some innocent beginner having been gulled into doing something fiddling, painstaking, difficult, but generally unnecessary.



Ah - your objection is to the process, not the words. I understand.

BugBear


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## CStanford (5 Dec 2013)

Jacob":76c5gexg said:


> Hollow. Most new chisels are like this. Flattening them is a mistake, same as flattening one of those hollow faced jap chisels. It makes sharpening easier.



If you can move the burr back to the beveled side of the chisel in one, or at most two short, little jabbing strokes on your fine stone (with chisel laid flat) then your chisel backs are functionally perfectly flat.

I strongly suspect that you are working with functionally perfectly flat chisel backs whether you intended it or not.


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## RossJarvis (5 Dec 2013)

Jacob":xrbs06hj said:


> Because whenever I see the words "lapping" or "prepping" in these forums, it seems to entail some innocent beginner having been gulled into doing something fiddling, painstaking, difficult, but generally unnecessary.



Being one of those innocent beginners I'd have to agree with you #-o . As an ex-engineering worker I still like the word and process of lapping, although it's often mis-used. I consider it a form of long meditation [-o< .

I also wonder how many poor decent planes have had their soles/bottoms/flat bits ruined by being rubbed on abrasive papers on glass/granite/iron  . This tends to wear the edges away a lot faster than the middle and generally leads to convex surfaces, unless done with an experienced sensitive touch and continual checking.


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## CStanford (5 Dec 2013)

RossJarvis":18sw4vzm said:


> Jacob":18sw4vzm said:
> 
> 
> > Because whenever I see the words "lapping" or "prepping" in these forums, it seems to entail some innocent beginner having been gulled into doing something fiddling, painstaking, difficult, but generally unnecessary.
> ...



A very slight convexity in sole from front to back or even side to side is not necessarily a bad thing on a handplane. Think about it. Buy a cheap plane and work a little convexity into it and see if it doesn't become your favorite smoother. This is very easy to try out on a vintage woody and easy to put back if you don't notice the value.


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## bugbear (5 Dec 2013)

CStanford":2nd0edce said:


> A very slight convexity in sole from front to back or even side to side is not necessarily a bad thing on a handplane.



Before the flames start, could you please quantify "very slight"? That could mean all things to all men.

BugBear


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## CStanford (5 Dec 2013)

bugbear":17tww5wr said:


> CStanford":17tww5wr said:
> 
> 
> > A very slight convexity in sole from front to back or even side to side is not necessarily a bad thing on a handplane.
> ...



I have no idea. I'm unable to measure it. A glint of light in the indictative places under the blade of Starrett combination square both ways - toe to heel and side to side. 

Try it! Every now and then a fish enjoys a venture away from the school.

Before everybody goes popping off this isn't meant for every plane you own or ever will own. Try it on a smoother and try it on a jack. Get a cheap woody that you can play around with.


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## Cheshirechappie (5 Dec 2013)

For a smoothing plane sole, I'd agree that a (very slight) convexity is not a disadvantage, and may even be advantageous at times. 

However, for a chisel, convexity of the flat face is best avoided, and if the flat face is to err from flat, a very slight concavity (of no more than five thousands of an inch or so over it's length from edge to shoulder) would be preferable.


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## CStanford (5 Dec 2013)

Cheshirechappie":hwpebpbv said:


> For a smoothing plane sole, I'd agree that a (very slight) convexity is not a disadvantage, and may even be advantageous at times.
> 
> However, for a chisel, convexity of the flat face is best avoided, and if the flat face is to err from flat, a very slight concavity (of no more than five thousands of an inch or so over it's length from edge to shoulder) would be preferable.



Agree. My comments were specifically about planes though certain carving chisels do have more complex geometry than one face flat, one face beveled.


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## bugbear (5 Dec 2013)

CStanford":z0cg0b4j said:


> bugbear":z0cg0b4j said:
> 
> 
> > CStanford":z0cg0b4j said:
> ...



Taking the combo square rule as a good enough straight edge, you'd just need 3 feeler gauges (these are cheap) to measure the convexity.

Just put "thick enough" feeler gauges between the rule and plane at the ends (say 20 thou), and then measure the gap in the middle of the plane with the third set.

Simple arithmetic then gives the convexity.

BugBear


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## RossJarvis (5 Dec 2013)

CStanford":2r5jdymx said:


> Cheshirechappie":2r5jdymx said:
> 
> 
> > For a smoothing plane sole, I'd agree that a (very slight) convexity is not a disadvantage, and may even be advantageous at times.
> ...



I was thinking more about planes where a well meaning but over-enthusiastic "flattening" by putting one's weight onto the handles would produce something more like a Weeble or Rocking Horse. However I was drifting away from the original topic somewhat. I would be interested though in any articles about plane set-up for jointing/flattening stock as it might seem that a concave sole would be beneficial to some extent here. Anyone know any links? (sorry if it's a bit off-topic).


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## MIGNAL (5 Dec 2013)

Whenever my wooden planes are not performing as well as they normally do I can virtually guarantee that there is convexity just in front of the mouth. Convexity, the way Japanese planes are usually set up, is perfectly fine. May even be desirable.

Oops. Of course I meant concavity. Thanks to BB.


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## David C (5 Dec 2013)

I will confirm that slight convexity in either direction, on a plane sole, works well. Naturally I am talking about 5s and 5 1/2s which I use as long smoothers.

The last one I measured, with reference to a Starret straight edge, was showing about 1 thou" gap at either edge, and toe & heel. 

I'm sure I have worked in the past with planes which were more convex than that, as we were less skilled. 

However even those were a huge improvement on what Stanley were selling in the 70s and eighties.

David Charlesworth


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