japanese chisel doubt

[GEPPETTO]

Hi All,
it's jumped in mind a doubt about japanese chisel sharpening. Apologize if the question is stupid but it's better to ask than to have doubts
OK I come to the question... You teach me a keen chisel edge can be achieved only if the flat side of the blade is very flat. In normal chisel i can have the flat onto the entire length of the blade.. flat after a lot of sharpening,too. Isn't it the same onto a japanese chisel, or no? What does it happen when I arrive to the hollow zone? Can Japanese chisels be sharpened up to the start of the pole?
Someone could say:" What did you learm here? Nothing!!".
Apologize again for the odd question

Many cheers
Gabriele :wink:

 

[scooby]

Hi All,
it's jumped in mind a doubt about japanese chisel sharpening. Apologize if the question is stupid but it's better to ask than to have doubts
OK I come to the question... You teach me a keen chisel edge can be achieved only if the flat side of the blade is very flat. In normal chisel i can have the flat onto the entire length of the blade.. flat after a lot of sharpening,too. Isn't it the same onto a japanese chisel, or no? What does it happen when I arrive to the hollow zone? Can Japanese chisels be sharpened up to the start of the pole?
Someone could say:" What did you learm here? Nothing!!".
Apologize again for the odd question

Many cheers
Gabriele :wink:

You don't have to flatten the entire length of the chisel. Just 2-3mm back from the edge is usually good enough. The japanese chisels prove this point as you only flatten a small area near the edge and retain as much of the hollow as possible. Then when the chisel is slowly worn down in length there is always the hollow to make subsequent flattening much easier.

 

[Frank D.]

Hi guys,
Japanese chisels have the hollow to save time flattening, so flattening the whole back is not too difficult (Japanese steel is hard). All that needs to be flat is what touches the wood; that is what registers the blade with respect to the surface of the wood. Since the hollow doesn't touch the wood, you only have to flatten the tip, the sides, and the very back. It's kind of like the corrugations on a plane: even though the whole sole doesn't come into contact with the wood (with a corrugated sole), it is still as flat as a solid sole with no corrugations.
That's my take on it anyway. I'd like to hear what others have to say.
Here's my useless pic (eat your heart out Philly!):

 

[Philly]

Gabriele
As the chisel gets worn with use the hollow gradually creeps closer to the edge. To re-establish the flat at the edge you need to lap the back whilst focussing pressure at the front of the chisel. This will "move" the hollow back.
Nice gloat Frank-I am paying attention :wink:
Hope this helps
Philly

 

[Frank D.]

gee,
Now I see I misunderstood the question...sorry Gabriele!

 

[GEPPETTO]

Gabriele
As the chisel gets worn with use the hollow gradually creeps closer to the edge. To re-establish the flat at the edge you need to lap the back whilst focussing pressure at the front of the chisel. This will "move" the hollow back.
Nice gloat Frank-I am paying attention :wink:
Hope this helps
Philly

Hi Philly, let's say we flatten the same length onto the normal and japanese.. let's say 2 mm.. hence.. Will I have the same time spent :? . If it is, hollow type is useful only when you buy the chisel and want to flatten yourself the back for e better result :? or not?

Cheers
Gabriele :wink:

 

[Frank D.]

Flattening the backs of chisels is not like flattening the backs of plane blades. An absolutely flat (or as close as possible) surface on the back is more important for chisels than plane blades because the back of the chisel acts like the sole of the plane: it registers the cut. Any curve on the back and you have to lift the chisel so the edge cat make contact with the wood or so the chisel will cut straight, which means less control and precision. That's why I think it's important to keep the back flat by lapping or polishing the whole surface, not just a few mm from the edge like you can for a plane blade. The hollow on Japanese chisels makes this easier to do (saves time both flattening and polishing).

 

[David C]

When I reach the hollow, five minutes spent on an 800grit waterstone will remove enough metal (from the back), to "move" the hollow back about 3 or4 mm.

3mm of exceedingly hard Japanese carbon steel should keep you working for a long time if you are careful with your sharpening.

The hardness of japanese steel is infinitely preferable to most softer european alloy steels, if they suit your style of cutting.

Prying and levering can be disastrous if you do not choose appropriate angles.

Do try one!

David Charlesworth

 

[Philly]

Gabriele
I find the hollow back gives less friction than a regualr one. This can be handy with wider chisels. As to wear, well as David C says the steel is VERY hard and durable.
Try one and see if you like it.
Hope this helps
Philly

 

[GEPPETTO]

Many thanks to everyone :wink:

Cheers
Gabriele