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12th May 2015, 10:31 PM #1Novice
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New koyamaichis oire-nomi / sharpening.
hey guys just received new set of koyamaichis from stu. my chisels from 18 mm down all have pretty high bevels that are not the same from 35 degrees and higher. what would be your technique to bringing them down to 30. i have water stones 1k 5k 8k and a tormerk. New to japanese chisels so wanted to get some tips before i touch them.
cheers
mark
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13th May 2015, 02:29 AM #2
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
DerekVisit www.inthewoodshop.com for tutorials on constructing handtools, handtool reviews, and my trials and tribulations with furniture builds.
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13th May 2015, 05:39 AM #3
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:
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13th May 2015, 05:48 AM #4GOLD MEMBER
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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).
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13th May 2015, 11:36 AM #5Novice
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13th May 2015, 11:40 AM #6Novice
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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
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13th May 2015, 11:42 AM #7Novice
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If they were all roughly 35 degrees I wouldn't worry but some are at 45 and 40 way to high.
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13th May 2015, 12:07 PM #8Member
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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..
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13th May 2015, 05:14 PM #9
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
DerekVisit www.inthewoodshop.com for tutorials on constructing handtools, handtool reviews, and my trials and tribulations with furniture builds.
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13th May 2015, 09:20 PM #10Novice
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