Chisel backs

[woodbrains]

Hello,

100% agree that this work is a real pain, it is not as if I like it, either. Never calculated the volume of steel removed before!

Mike.

 

[Corneel]

Just went out to the shop (instead of continueing to be lazy). I spend half an hour with an 1/2"chisel on 120 grit sandpaper and had the feeling that I was getting nowhere. All in the name of science! Tomorrow I'll buy some fresh 80 grit, but I won't promiss any updates soon.

 

[Jacob]

Hello,

100% agree that this work is a real pain, it is not as if I like it, either. .....

Well stop doing it then! If it really is necessary (very unlikely) just get another chisel.

 

[woodbrains]

Hello,

100% agree that this work is a real pain, it is not as if I like it, either. .....

Well stop doing it then! If it really is necessary (very unlikely) just get another chisel.

Hello,

All mine are done now :lol: not that they needed much in the first place, I don't buy things new or old that are to bad to begin with.

Mike.

 

[Corneel]

In the name of science, I have corrected one of my bellied chisels. This one is 16mm wide and the flat iron bit is something like 11 cm long. Made bij Berg in Sweden. It came to me with a very noticable belly, you could rock it back and forth on a straight edge. I had it flattened and polished an inch or so from the edge. And used it like that for years.

In light of this discussion I glued some strips of 80 grit to a glass plate. Two narrow strips and one full width. I started on the narrow ones to remove the belly (hard to do when sanding all the length of the chisel in one go).


After a while the sanding paper lost its effectiveness. I could have glued a new piece to the glass, but I was impatient and went to the stones. 400, 1000, 4000 and 8000 grit. Carefully flattened of course and making sure all of the stone was equilly used. As usual it takes a lot of time to go from the sandpaper to the stones. Somehow they never match immediately. Overall it took me 2.5 hours to create an ideal chisel. Not too bad, I thought it would have taken longer.



I am not going to give my other chisels the same treatment. I'm pretty sick of it all ready. Some observations:
When someone tells you that it takes a few minutes to flatten a chiselback, don't believe them. (Sorry Mike).
In David Charlesworth's book you can read how he flattens chisel backs, starting with an 800 stone. That must be pure torture with a chisel like this. Start with the coarsest grit you have.
The sandpaper I can get isn't optimal for steel. I'll ask around here if I can find something better, especially longer lasting. Maybe this is an ideal job for diamonds, but you always only hear about very fine diamonds for polishing, not the coarse ones.
When I started to read the woodworking forums, about 6 years ago, it was very common to see someone showing a picture like this, very proudly. I think times are a changing. You don't see this very often anymore. Most people will advice you to polish half an inch or so. Which I think is great advice.

 

[David C]

Ah but Corneel, In the beginning I was advised not to buy bellied chisels, and I paid good attention to this councel. I have sent many many chisels back to the manufacturer or retailer. A correctly ground English chisel has the slight concavity in length which is so beneficial for preparation and sharpening.

By the way, the reason your scrub blade is not working in your guide, is that it is in the chisel slot. My L-N blade fits in the plane blade department.

David Charlesworth

 

[Jacob]

..... A correctly ground English chisel has the slight concavity in length which is so beneficial for preparation and sharpening.

Yes and this mean sharpening takes about a minute and you are off.
If they need "preparation" they should be sent back - it's the tool maker's job, they have got all the kit.
Unfortunately, due to the great mass of misleading information around this topic, innocent beginners are buying top class tools, wasting hours of time and spoiling them by "prepping" them. "Prepping" - stupid name, stupid idea!
flattening-chisel-backs-with-lapping-film-t68506-225.html

This is as much flattening and polishing you need on a typical new chisel face:

And this chisel would be perfectly flat enough for woodbrain's half blind DT paring problem, even though it is convex by about 1.5mm in the middle

By the way, the reason your scrub blade is not working in your guide, is that it is in the chisel slot. My L-N blade fits in the plane blade department.

David Charlesworth

Too narrow for the plane slot and much easier freehand anyway. Why struggle? Is it possible to do a scrub plane blade in a jig anyway, bearing in mind it has to be turned through quite an angle to get the camber?
Just because you have got a jig doesn't mean you have to use it! Try it without training wheels!

 

[Cheshirechappie]

I think Ashley Iles aim for about 3 to 5 thou concave on their b/e chisel flat faces. I'd have said that 1.5mm (1/16", about 0.060") is a bit too much concavity on a chisel expected to do good class work.

How fussy you are about flat face flatness depends what you want the chisel to do. For really rough work, 1/16" might well be acceptable. For fine cabinetmaking and similar precision work, the AI concavity seems to me to be more appropriate.

I'd say the same about a belly in the flat face, too. Preferably none at all for fine work, but for rough carpentry a bit of bellying could be acceptable.

In the end, however, it's the results that count. If the chisel does what you want it to, easily and without needing undue manipulation, it's in good enough order. The only time to worry about chisel flat face flatness is when the chisel won't do what you want it to. The moral of this story is - when you aquire new chisels, be they brand new or vintage, sharpen them up and test them out before you spend time on correcting faults that may be immaterial.

Aiming for optical degrees of flatness just seems pointless for any woodworking task, however precise. I suppose it wouldn't do much harm, but it's hard to see how it would be beneficial, either. After all, wood will 'give' a bit as it's being worked, and will move a bit with climatic conditions over time. Treating wood like a high precision grade of toolsteel suitable for gauge-making really is pointless.

 

[Jacob]

I think Ashley Iles aim for about 3 to 5 thou concave on their b/e chisel flat faces. I'd have said that 1.5mm (1/16", about 0.060") is a bit too much concavity on a chisel expected to do good class work.

Why? I keep asking this but nobody ever answers! 1.5mm in the length of a chisel is getting on for 0.1mm in the end few mm which is reduced again by flattening (see photo above) which is doing the work. And what is the problem with "belly" exactly? All chisels will end up slightly less than concave - should we bin them? I think not.

.... The moral of this story is - when you aquire new chisels, be they brand new or vintage, sharpen them up and test them out before you spend time on correcting faults that may be immaterial..... Treating wood like a high precision grade of toolsteel suitable for gauge-making really is pointless.

Definitely!

 

[woodbrains]

Hello,

Wow, Corneel 2 1/2 hours on the back of a chisel. I'm sorry if I encouraged you to do this, but I have never in my life spent even close to that sort of time. I can only conclude that it must have been a dog of a tool. Maybe it was misused and bent, perhaps, to need so much work. If it was as far out as this amount of time would suggest, then it couldn't have been much use, so take some gratification that yo have produced a workable tool from a relative junker.

I once had a 5 jack plane that had 10 thou needing removing from the entire sole, but even that did not take 2 1/2 hours. Hats off to you for perseverence! =D>

Mike.

 

[Paul Chapman]

Is it possible to do a scrub plane blade in a jig anyway, bearing in mind it has to be turned through quite an angle to get the camber?

As I said before, I can't understand why you feel it necessary to hone the whole of the camber on a scrub plane. Just checked mine and I hone a central portion which amounts to about half the camber. I can't imagine that you ever have anywhere near the whole of the camber projecting when using the plane.

Must be quite entertaining watching you freehand hone the camber at the same time as maintaining a rounded bevel - all at the speed of light, of course

Cheers :wink:

Paul

 

[Corneel]

Hello,

Wow, Corneel 2 1/2 hours on the back of a chisel. I'm sorry if I encouraged you to do this, but I have never in my life spent even close to that sort of time. I can only conclude that it must have been a dog of a tool. Maybe it was misused and bent, perhaps, to need so much work. If it was as far out as this amount of time would suggest, then it couldn't have been much use, so take some gratification that yo have produced a workable tool from a relative junker.

I once had a 5 jack plane that had 10 thou needing removing from the entire sole, but even that did not take 2 1/2 hours. Hats off to you for perseverence! =D>

Mike.

Well, in that case I'd like to see some tips! Maybe it's the sandpaper, I use 3M sandblaster, whatever that is, they don't tell on the package. I feel it really wears out too soon on metal. Like I said, I need to find something aimed at the metalworker. Another point, it always takes me a long time to go from the sandpaper to the stones. If it looks perfect after the sandpaper, I usually only get around half of the surface on my 400 stone. So that takes considerable time. As soon as it is fine on the 400 stone, it doesn't take too long anymore on the rest of the stones.

The chisel had a convexity about 0.2mm. Meassured with a piece of paper. One paper easilly slipped under the chisel, 2 didn't, and the paper was 0.15mm thick. So it wasn't terible, just obviously convex and I have used it a lot. This chiselset was my only set for quite some time. There are more with various amounts of convexity.

When buying new chisels it's easy. They should look like the picture from Jacob. But I like to buy old ones, and many old chisels are convex like this. Jt makes you wonder, didn't they care at all, back in the day?

And don't worry about this little experiment. It was fun, in a perverse kind of way.

 

[Corneel]

Ah but Corneel, In the beginning I was advised not to buy bellied chisels, and I paid good attention to this councel. I have sent many many chisels back to the manufacturer or retailer. A correctly ground English chisel has the slight concavity in length which is so beneficial for preparation and sharpening.

By the way, the reason your scrub blade is not working in your guide, is that it is in the chisel slot. My L-N blade fits in the plane blade department.

David Charlesworth

Ah yes, the new chisels. But I like vintage stuff.

And indeed, the scrub plane blade was too narrow. Which kind of proves my little theory that not every tool fits in a jig. I'm sure you can find something in your shop too.

Moulding planes don't fit in a jig either.

http://pegsandtails.wordpress.com/2009/11/10/sharpening-a-moulding-plane/

 

[G S Haydon]

 

[David C]

Jacob,

Please do not be more obtuse than you have to.

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

It probably means grinding and honing the bevel as well.

The fact that a certain curved blade can be done with a cheap jig is a matter of interest to some.

Here are some of your helpful observations on honing guides.

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

I would say singularly missleading.

David

 

[woodbrains]

Well, in that case I'd like to see some tips! Maybe it's the sandpaper, I use 3M sandblaster, whatever that is, they don't tell on the package. I feel it really wears out too soon on metal. Like I said, I need to find something aimed at the metalworker. Another point, it always takes me a long time to go from the sandpaper to the stones. If it looks perfect after the sandpaper, I usually only get around half of the surface on my 400 stone. So that takes considerable time. As soon as it is fine on the 400 stone, it doesn't take too long anymore on the rest of the stones.

The chisel had a convexity about 0.2mm. Meassured with a piece of paper. One paper easilly slipped under the chisel, 2 didn't, and the paper was 0.15mm thick. So it wasn't terible, just obviously convex and I have used it a lot. This chiselset was my only set for quite some time. There are more with various amounts of convexity.

When buying new chisels it's easy. They should look like the picture from Jacob. But I like to buy old ones, and many old chisels are convex like this. Jt makes you wonder, didn't they care at all, back in the day?

And don't worry about this little experiment. It was fun, in a perverse kind of way.

Hello,

This may be inaccurate, but I'm fairly sure 3M sandblasted is aluminium oxide abrasive. Not the best for metal, and if I recall is for decorators sanding between coats of paint. Whatever, you need silicon carbide abrasive, it holds its aggressiveness much longer. Ali oxide is friable when sanding wood, so must break down very quickly on steel. Also, what stones are you using? Japanese, American and European abrasives are graded differently, so you may be making a too big a leap in abrasive grits when you move from the paper to the stones. This is why I always use microns when I compare abrasives, ( much to Jacob's dismay! But there is a good reason) so there is some weans of parity.

Even if the 3M sandblasted is Si C, it is open coated to help with waste material for sanding paint, there is a lo less abrasive available so will not perform as well, and open coated paper is not needed for the task you require.

Mike.

 

[Corneel]

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

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

 

[Corneel]

Was sitting in the train so had plenty of time to think a bit more. There is more to grit size then just the number from the comparison charts. Grit breaks down. I'm sure when you keep at it long enpough, you could polish with just a piece of 80 grit. My sandpaper wasn't 80 grit anymore by the time I went to the stone. The 400 stone doesn't have a lot of trouble to remove the scratches from the sandpaper. But there is something else going on. The sandpaper seems to create a different surface in the metal then the stone. Probably because of the way the paper and the glue moves under the pressure.

I also have a Sigma 120 stone, but that is a weird stone. Hard to get it working to my liking. It leaves really deep scratches, it wants to load and clog easilly while it is hard to get clean again.

Anyway, I still do need better sandpaper.

 

[Jacob]

It's called "emery" or "wet and dry" paper. As used by metal workers and mechanics, available in motor spares , tool, cycle and DIY shops.
Grit sizes is misleading as there are different materials and different ways of putting them together which makes a big difference to how they perform. I stick to coarsest to finest arranged roughly in apparent order. Unless it is specified you may never know the grit size anyway.

 

[Corneel]

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

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