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View Full Version : Suggested starting angle to sharpen new Tojiro DP Gyuto and Petty?



GeneH
05-13-2013, 10:52 AM
I have a new Tojiro DP 180mm Gyuto and a 120mm Petty waiting for me when I get home from the office in a couple hours. Assuming I can improve the bevel, how shallow should I take it? This will be a straight V, not convexed. I guess this VG10 core is about a 60-something in the rockwell scale, so does it perform better a little toothy (about 1500 grit, sorry don't have the micron size) or should I smooth it out a bit for starters?

Mike9
05-13-2013, 11:12 AM
According to Tojiro the factory angle is between 9 and 12 degrees. Lay a straight edge across each side to see if it's 50/50 or asymmetric.

franzb69
05-13-2013, 11:25 AM
tojiro dp's are said on their website to be 60/40 righty biased. but it really depends on how it's made if it's machine sharpened or hand sharpened. i'd follow what mike9 said.

GeneH
05-13-2013, 11:45 AM
tojiro dp's are said on their website to be 60/40 righty biased. but it really depends on how it's made if it's machine sharpened or hand sharpened. i'd follow what mike9 said.


Yikes! I thought they were 50/50 symmetrical blades. I'm a lefty. If it's just the cutting bevel that's biased, I can fix that but not if the whole blade is asymmetrical.

jgraeff
05-13-2013, 12:05 PM
you can make it 50/50 with no problem or even 60/40 lefty. It will take some work but if you new i would just follow bevels until your comfortable. Watch theorys sharpening gyuto video it explains how you sharpen until you get a burr then flip rather than counting strokes and really is the best way to sharpen.

If the blade is asymmetrical it may cause sticking on the left side.

Benuser
05-13-2013, 12:11 PM
The difference between a 60/40 and a 50/50 is barely perceptible. Would it steer - which is not very likely - I would suggest to convex the left side a bit by thinning behind the edge, and loosen your grip.

GeneH
05-13-2013, 12:35 PM
So - How do I tell if the blade, (not the bevel) is symmetrical or not? Do I use the flat side of the handle as a reference? That doesn't sound reliable to me. I'm outa my league here.

stevenStefano
05-13-2013, 12:53 PM
I used to find it tricky but not now. Hold it up blade side up and look at it down the choil if you get me. Does one side of the knife look different to the other? If it's 50/50 clearly the sides will look the same but if one side is convex (more rounded) and the other is flat then that shows an asymmetric grind. If you take a photo it would help. I've got a DP damascus and it looks 50/50 to me or close

GeneH
05-13-2013, 04:36 PM
tojiro dp's are said on their website to be 60/40 righty biased. but it really depends on how it's made if it's machine sharpened or hand sharpened. i'd follow what mike9 said.

I think I found the info you are referring to, "In our factory we edge the blade 60% to the right and 40% to the left, because it is quite difficult to edge fifty-fifty by standard grinding. However it is also possible to edge conversely upon request." http://tojiro.net/en/guide/part_edge.html

Since it is the edge being discussed, I'm good with that. Easy enough to change, but if the factory has a problem getting and even 50/50 edge, I doubt I could do better. Why would a company say it's "quite difficult" so they proclaim 60/40? Sounds like just a way to justify an uneven bevel, so bias it on purpose one direction.

The knives arrived - wooohooo! For the life if me I cannot see that the blade itself is asymmetrical. They are the F807 and F801 Western style.

dannynyc
05-13-2013, 05:25 PM
Did you ever measure that factory angle? I'm skeptical that a Tojiro would have a 9-12 angle, I would think closer to 15.

tk59
05-13-2013, 06:05 PM
Tojiros are pretty chippy and not particularly fine-grained. You'd be best served sharpening at whatever angle you desire and then putting a micro on it at a high angle. I also wouldn't worry too much about the asymmetry. I've never noticed it, myself.

Squilliam
05-13-2013, 06:49 PM
I thin mine almost to the point of burr formation at 5 degrees then put a 20 degree microbevel on each side to prevent chipping.

Benuser
05-13-2013, 07:21 PM
I think I found the info you are referring to, "In our factory we edge the blade 60% to the right and 40% to the left, because it is quite difficult to edge fifty-fifty by standard grinding. However it is also possible to edge conversely upon request." http://tojiro.net/en/guide/part_edge.html

Since it is the edge being discussed, I'm good with that. Easy enough to change, but if the factory has a problem getting and even 50/50 edge, I doubt I could do better. Why would a company say it's "quite difficult" so they proclaim 60/40? Sounds like just a way to justify an uneven bevel, so bias it on purpose one direction.
It's quite difficult if you grind in two passes only, which is their standard procedure. They start grinding on the right side until a burr appears, switch side and do exactly the same on the left side, and then deburr. The first pass on the right side will take more time than the next one on the left side, so the edge will always be off-centered - to the left.
You may compensate by starting on the left side and going on until you have a burr. This will somewhat recenter the edge. Some loss of material is being involved, though.

Benuser
05-13-2013, 07:39 PM
This will be a straight V, not convexed. Why?
By the way, you'll have to go far beyond the 1500 grit to get your VG-10 properly deburred.

tk59
05-13-2013, 07:48 PM
Why?
By the way, you'll have to go far beyond the 1500 grit to get your VG-10 properly deburred.If you lighten up on the pressure and change the direction of your sweep, a 1500 will do okay. However, I do agree that 3k+ will make it easier.

GeneH
05-13-2013, 07:55 PM
Why? [V?]
By the way, you'll have to go far beyond the 1500 grit to get your VG-10 properly deburred.

I haven't managed freehanding, and don't see it in my future. (Ok, my tiny carving blades are freehand, but that's different) I just won't be sharpening enough to get and keep the muscle memory.

GeneH
05-13-2013, 07:59 PM
If you lighten up on the pressure and change the direction of your sweep, a 1500 will do okay. However, I do agree that 3k+ will make it easier.

I expect to get something like the Shapton's at around 2k and 4k eventually, but one thing at a time. (the 1500 keeps loading up so will replace it) I have actually been doing well on soft steel going from the 1500 stone to a strop with (6 - 10 micron maybe?) alu oxide powder and green crayon.

How about 1 micron boron carbide paste on leather?

tk59
05-13-2013, 08:01 PM
What are you using to sharpen?

GeneH
05-13-2013, 08:40 PM
What are you using to sharpen?

I hesitate to come out...but EP. Training wheels to some folks. Slow, repeatable, not very cost effective...but repeatable.

tk59
05-13-2013, 09:41 PM
Meh. That's not a big deal. What's worthy of ridicule is people who rationalize going around trying to cut things with dull knives. You can still change your pressure, direction of the scratches and the angle on an EP.

franzb69
05-13-2013, 11:04 PM
Since it is the edge being discussed, I'm good with that. Easy enough to change, but if the factory has a problem getting and even 50/50 edge, I doubt I could do better. Why would a company say it's "quite difficult" so they proclaim 60/40? Sounds like just a way to justify an uneven bevel, so bias it on purpose one direction.


they only say it's difficult for people new to knife sharpening. =D


Tojiros are pretty chippy and not particularly fine-grained.

i don't find my tojiro to be chippy at all.


Why?
By the way, you'll have to go far beyond the 1500 grit to get your VG-10 properly deburred.

i sharpen to around 5k.

tk59
05-14-2013, 12:43 AM
...i don't find my tojiro to be chippy at all...Good for you. I'm not going to guess why you don't find yours chippy but I've owned and/or fixed quite a few of them and I'm not the only one that's noticed.

franzb69
05-14-2013, 01:08 AM
Good for you. I'm not going to guess why you don't find yours chippy but I've owned and/or fixed quite a few of them and I'm not the only one that's noticed.

understood

=D

bought mine used, probably the previous owner took out enough steel that the stressed steel has been ground away. i dunno. lol.

GeneH
05-14-2013, 04:55 AM
... I've owned and/or fixed quite a few of them and I'm not the only one that's noticed.
Well if I do grind a new lower angle bevel and find the edge doesn't hold up under whatever my normal use is, it's easy enough to put a new primary or micro bevel on it.

But back to an earlier question - how about 1 micron boron carbide paste on my leather strop? Not too fine and not too course to use after a 4k or 5 k stone? In reality I guess I'm using strops as a fine, soft stone, (successfully) but sure seems less likely to screw up the edge.

mikemac
05-14-2013, 08:52 AM
The EP will do a great job, but unless it's the EP Pro, it only goes so low, and I think that may be 12*. After the EP, the loaded strop will do a good job , so have at it.
Personally, since you just got these, and these are your first foray into J-knives, I wouldn't screw with the blade or edge bevel...I'd recommend black marker on the edge, start with a little thinning behind the edge, then put a new edge on and finish with loaded strop. As a reference point, it's useful to know where you've started before you change something....

GeneH
05-14-2013, 12:17 PM
The EP will do a great job, but unless it's the EP Pro, it only goes so low, and I think that may be 12*. After the EP, the loaded strop will do a good job , so have at it.
Personally, since you just got these, and these are your first foray into J-knives, I wouldn't screw with the blade or edge bevel...I'd recommend black marker on the edge, start with a little thinning behind the edge, then put a new edge on and finish with loaded strop. As a reference point, it's useful to know where you've started before you change something....

Ya, that's a really good idea. I did my larger Chicago Cutlery chefs at a pretty shallow angle, then had to do a mini-bevel because it kept chipping and folding... I should have known better, but it was fun grinding it down and polishing it.

GeneH
05-14-2013, 06:14 PM
Well I rounded and polished the spine then cleaned up the bevels on the Petty. Measured about 12 1/2 deg, so take a little off for the blade angle itself, and that's a pretty thin bevel. I set the stones to match the shallowest part of the factory grind and am happy with that. And actually the 1500 worked pretty with just a little stropping. There are a few very tiny chips, presumably from the factory grind that I did not cut out, but not enough to warrant taking off more metal. The Gyuto is plenty good the way it is.

Benuser
05-14-2013, 10:51 PM
Tojiros are pretty chippy and not particularly fine-grained. You'd be best served sharpening at whatever angle you desire and then putting a micro on it at a high angle. I also wouldn't worry too much about the asymmetry. I've never noticed it, myself.
Do they stay chippy, even after a few sharpenings and the initial edge being removed?
Or is it microchipping as so often seen with brand new blades?

GeneH
05-18-2013, 09:26 AM
Originally Posted by tk59
Tojiros are pretty chippy and not particularly fine-grained. You'd be best served sharpening at whatever angle you desire and then putting a micro on it at a high angle.


Do they stay chippy, even after a few sharpenings and the initial edge being removed?
Or is it microchipping as so often seen with brand new blades?

Since no response from more experienced users, I'll let you know after a couple months. But if I read tk59 correctly, they stay chippy.

franzb69
05-18-2013, 11:02 AM
i bought my gyuto as used so i can't tell if it started out as chippy, all i know is that mine isn't chippy at all. i also have another vg10, a shun santoku. bought it for my mom. hers is doing fine as well. bought it new. also vg10, of course.