Thread: New koyamaichis oire-nomi / sharpening.

What type of chisels are they? Bench (which require a 30 degree bevel) or slicks (which use a 25 degree bevel). Then, again, a mortice or heavy duty chisel would use 35 degrees.

Regards from Perth

Derek

Different Smiths use a range of angles and they can range widely from the same smith. The bevels are hand ground and there seems to be a fair amount of variance my Ouchis came to me plus/minus 35º. My Kikuhiromaru were at plus/minus 30º. I have a feeling that the smith form the bevel angle relative to his faith or confidence in his skill. I started out lowering bevel angles on my Japanese chisels so they were all the same 30º, in hind sight it would have been better to use the angle the smith gave me.

The problem with Japanese chisels is that the edges are not square to the bevel and not parallel to each other. They tapper front to back. My Kikuhiromaru taper as much as 1 mm in their width. This makes using a jig problematic as jigs tend to assume that the edge is square to the bevel, i.e. made for western industrial tools. With Japanese chisels the bevel must not be square to the edge but perpendicular to the tang/handle.

General advice is not to use a grinder even a slow speed grinder, because hollow grinding can overheat the lamination and two it weakens the edge, by removing the softer backing steel.

Since the chisel is laminated it is a easy task to reduce angles since honing on a #1000 stone quickly removes the soft backing steel.

I would not be to concerned about having some idealised specific angle.

Learn to hone your chisel by hand, if you want to reduce the angle slight shift in hand pressure towards the back of the bevel will over a few sharpening reduce your bevel angle.


I would start by watching these videos:

Medium Crystolon stone (or any generic equivalent you might have in australia for cheap). You'll be surprised how fast it cuts them.

Personally, I'd grind them, but I don't think most people should do that.

Leave the narrow ones a little steeper than the others.


(the medium crystolon is a nice stone to have even if you only use it for something else - it is the best grinding stone, bar none, though you will probably have to use it with oil. Make sure it's a new one, they get hard as they get old and they don't work well when they're extremely hard).

Originally Posted by derekcohen

What type of chisels are they? Bench (which require a 30 degree bevel) or slicks (which use a 25 degree bevel). Then, again, a mortice or heavy duty chisel would use 35 degrees.

Regards from Perth

Derek

hey derek they are bench chisels, I'm confident honing by hand I was going to purchase Dimond stone 400/1000 to bring it down. Or should I just leave them and over time bring it down.

thanks
mark

Originally Posted by thumbsucker

Different Smiths use a range of angles and they can range widely from the same smith. The bevels are hand ground and there seems to be a fair amount of variance my Ouchis came to me plus/minus 35º. My Kikuhiromaru were at plus/minus 30º. I have a feeling that the smith form the bevel angle relative to his faith or confidence in his skill. I started out lowering bevel angles on my Japanese chisels so they were all the same 30º, in hind sight it would have been better to use the angle the smith gave me.

The problem with Japanese chisels is that the edges are not square to the bevel and not parallel to each other. They tapper front to back. My Kikuhiromaru taper as much as 1 mm in their width. This makes using a jig problematic as jigs tend to assume that the edge is square to the bevel, i.e. made for western industrial tools. With Japanese chisels the bevel must not be square to the edge but perpendicular to the tang/handle.

General advice is not to use a grinder even a slow speed grinder, because hollow grinding can overheat the lamination and two it weakens the edge, by removing the softer backing steel.

Since the chisel is laminated it is a easy task to reduce angles since honing on a #1000 stone quickly removes the soft backing steel.

I would not be to concerned about having some idealised specific angle.

Learn to hone your chisel by hand, if you want to reduce the angle slight shift in hand pressure towards the back of the bevel will over a few sharpening reduce your bevel angle.


I would start by watching these videos:

Hey thumbsucker thanks for the advice I was going to freehand it on the tormek then take it to the stones, but now that you mentioned you should of just left them how they were Mabey I'll do that. As with the 3mm chisel would you leave it with more bevel.I think it's at 35.

thanks
mark

If they were all roughly 35 degrees I wouldn't worry but some are at 45 and 40 way to high.

It is also a matter of the wood you are going to choose. Medium hardwoods (cherry like) will take 32-34 nicely... 35 might be just a little bit too high - but then again, i do not know the specific steel was used... Just try them like that and take it from there. Trust your feelings - they will tell you where you should go..

Originally Posted by M.cedro

hey derek they are bench chisels, I'm confident honing by hand I was going to purchase Dimond stone 400/1000 to bring it down. Or should I just leave them and over time bring it down.

thanks
mark

Hi Mark

30 degrees is a good balance. If some are 40 degrees, I'd redo the angles.

Two options:

1. Use a honing guide and set it for 30 degrees. Begin on coarse sandpaper, about 120 grit, then move to your 400 and 1000. Finish on approx. 8000. The honing guide is the key here - just to reduce the effort of grinding.

2. Grind the angle with a Tormek. I would not worry about the hollow. It will disappear quickly as the 10" wheel leaves it shallow, and the wet surface keeps the edge cool. Then go to your 1000 and 8000.

Regards from Perth

Derek

Originally Posted by derekcohen

Hi Mark

30 degrees is a good balance. If some are 40 degrees, I'd redo the angles.

Two options:

1. Use a honing guide and set it for 30 degrees. Begin on coarse sandpaper, about 120 grit, then move to your 400 and 1000. Finish on approx. 8000. The honing guide is the key here - just to reduce the effort of grinding.

2. Grind the angle with a Tormek. I would not worry about the hollow. It will disappear quickly as the 10" wheel leaves it shallow, and the wet surface keeps the edge cool. Then go to your 1000 and 8000.

Regards from Perth

Derek

thanks for the info derek I'll bring them all to around 30 degrees. Looking forward to putting these to some good use.

Cheers
mark cedro