Sharpening Recurve on Edge Pro

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dv/dt
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Sharpening Recurve on Edge Pro

Post by dv/dt » Sat Feb 18, 2017 2:18 pm

Not for a kitchen knife, but I have an Edge Pro question. I have a ZT 0350 and I'm trying to figure out the best way to sharpen it. The standard width stones won't work. I read that you could use 1/2" stones, but CKTG doesn't carry them. My knife wasn't that sharp ootb, so I want to put a good edge on it and keep it that way. What's the best way to sharpen this knife?

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ChefKnivesToGo
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Re: Sharpening Recurve on Edge Pro

Post by ChefKnivesToGo » Tue Feb 21, 2017 1:44 pm

We used to sell the half inch stones but they still were not ideal. It took a lot of work to round down the edges of the stones.

I wonder if a rounded piece of soft wood like basswood, mounted to the plate and then loaded with CBN or Diamond Paste. That way you could sand a nice half circle so it would work it's way around the inside of that curved blade.
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SteveG
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Re: Sharpening Recurve on Edge Pro

Post by SteveG » Tue Feb 21, 2017 2:16 pm

I've sharpened a friend's ZT 0350 free hand using the corner of a couple Shapton Glass stones for the recurve portion of the blade. It worked quite well, though you'll round the edge a little on the stone. As long as there's clearance to the metal backing plate, I could see rotating a standard EP Shapton Glass stone while you're working the rod so you're hitting the edge (corner) of the stone instead of the normal flat for the recurve portion.

Based on Mark's idea, you could also try wrapping wet/dry sandpaper around the stone holder rod and work that into the recurve area.

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ken123
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Re: Sharpening Recurve on Edge Pro

Post by ken123 » Sat Mar 11, 2017 8:44 pm

recurveShapton1.jpg
recurveShapton2.jpg
recurveShapton3.jpg

Here's some examples of stones I cut for a customer doing recurves.

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Ken

DarkStar
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Re: Sharpening Recurve on Edge Pro

Post by DarkStar » Sun Mar 12, 2017 9:46 am

Seems like rounded stones would rather quickly change shape and complicated matters. Wondering how long they would be effective.

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ken123
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Re: Sharpening Recurve on Edge Pro

Post by ken123 » Mon Mar 13, 2017 2:48 am

Depends on the hardness of the stone and how well you maintain them. As with maintaining flatness, you would maintin curvature with small touchups rather than drastic reshaping. Sword polishers do this on their stones and maintain them for years, passing them down in their family. YMMV.

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Re: Sharpening Recurve on Edge Pro

Post by DarkStar » Mon Mar 13, 2017 7:13 am

Thanks!!

adishdelish
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Re: Sharpening Recurve on Edge Pro

Post by adishdelish » Mon Mar 27, 2017 9:19 pm

I recently started using the Apex for sharpening recurves and found that I could get good results by knocking off the sharp edges of the standard stones with a diamond flattening stone. Nothing drastic, just a slight rounding to the edges of the stones. Also, when making contact with the blade, you should be careful when the stone contacts two points of the blade leaving a gap between the middle of the stone and the curve of the blade. I found that if I didn't lighten up the pressure on the leading side of the stone on the blade that the curve of the blade would become mishapen or elongated over time. I practiced with some lower quality blades first to get the feel for the right distribution of pressure. While the shape of the recurve makes it difficult to use a consistent angle of contact throughout the edge, the initial profiling of the blade with the lower grit stones should be done with care to avoid making a drastic difference between the sections of the blade that are further from the pivot point of the stone guide. I may do a video on future customer knives. If so, I will post the link here. Good Luck!

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Re: Sharpening Recurve on Edge Pro

Post by Radar53 » Tue Mar 28, 2017 5:01 pm

adishdelish wrote:
Mon Mar 27, 2017 9:19 pm
..... I found that if I didn't lighten up the pressure on the leading side of the stone on the blade that the curve of the blade would become mishapen or elongated over time. .....
I find that I can reduce this by moving some of the pressure to the trailing edge of the stone and / or making X (5 maybe) strokes from heel to tip & then doing the opposite of X strokes from tip to heel. YMMV
Cheers Grant

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ken123
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Re: Sharpening Recurve on Edge Pro

Post by ken123 » Tue Jun 27, 2017 10:20 pm

Here's another set of stones that I just finished for a customer. These are fully rounded half rounds. The previous set above was rounded but not going all the way to the base of the stone.

These are Nubatamas. The coarsest one is a 150 grit Bamboo. The rest are Nubatama Platinums, stones that specifically will handle abrasion resistant steels as well as anything available. Grits are 320 600 1500 and 3k.

Unlike stones with rounded off corners, they will just touch the recurve at one point, giving you more control.

You can use these both with the EP or freehand.

Image

Image

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Ken

lfholland
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Re: Sharpening Recurve on Edge Pro

Post by lfholland » Wed Jun 28, 2017 10:55 am

A friend of mine wants me to clean up the edge on his navy diver ka-bar. It has this type of profile:

http://www.survivaltech.pl/wp-content/u ... 302bx8.jpg

I think I'm going to try the wet dry sand paper on a dowel rod and do it by hand. Outside of buying a new set of stones, would that be the best approach?

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Re: Sharpening Recurve on Edge Pro

Post by Radar53 » Wed Jun 28, 2017 3:46 pm

Hi there lfh. Looking at the picture, the main edge looks to be pretty standard with no recurve. So I'm wondering if you talking about the bit 30 - 40mm from the end of the spine to the tip??
Cheers Grant

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lfholland
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Re: Sharpening Recurve on Edge Pro

Post by lfholland » Wed Jun 28, 2017 7:21 pm

Radar53 wrote:
Wed Jun 28, 2017 3:46 pm
Hi there lfh. Looking at the picture, the main edge looks to be pretty standard with no recurve. So I'm wondering if you talking about the bit 30 - 40mm from the end of the spine to the tip??
Yes, I'm talking about the curved and sharpened portion on the spine at the tip. If that's not recurve, then I apologize for using the wrong terminology. Should I start a different thread? Don't want to get this one off topic.

I already took care of the the main edge, but that other part is tricky.

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Re: Sharpening Recurve on Edge Pro

Post by Radar53 » Wed Jun 28, 2017 8:17 pm

No all good - I just wanted to make sure I understood what you were saying and that we were both on the same page.

If the recurve is in reasonable shape I think that the wet & dry automotive sand paper would work although I would use a larger diameter dowel, maybe an inch or more.

Other choices would be larger diameter (10mm?) ceramic rods & if the edge is not in good shape maybe start with a long elliptical diamond file to establish a good bevel & then go on to finer wet & dry grits following that.

Just my 2¢ worth!!
Cheers Grant

Just because you're not paranoid doesn't mean they're not going to get you!!

lfholland
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Re: Sharpening Recurve on Edge Pro

Post by lfholland » Thu Jun 29, 2017 10:42 am

Radar53 wrote:
Wed Jun 28, 2017 8:17 pm
No all good - I just wanted to make sure I understood what you were saying and that we were both on the same page.

If the recurve is in reasonable shape I think that the wet & dry automotive sand paper would work although I would use a larger diameter dowel, maybe an inch or more.

Other choices would be larger diameter (10mm?) ceramic rods & if the edge is not in good shape maybe start with a long elliptical diamond file to establish a good bevel & then go on to finer wet & dry grits following that.

Just my 2¢ worth!!
It's has a very wide angle, so the bevel is still there it's just very dull on the edge. A ceramic rod would probably work quite well, but I do not have one. I'm going to see what type of progress i make with the sand paper glued to a rod. I do have a Arashiyama 6K that arrived broken. I could try rounding a piece of it to finish it off.

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pjwoolw
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Re: Sharpening Recurve on Edge Pro

Post by pjwoolw » Thu Jun 29, 2017 5:28 pm

That portion of the knife isn't really supposed to be sharp. That is an Ontario Mk III IIRC.
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lfholland
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Re: Sharpening Recurve on Edge Pro

Post by lfholland » Fri Jun 30, 2017 1:02 pm

pjwoolw wrote:
Thu Jun 29, 2017 5:28 pm
That portion of the knife isn't really supposed to be sharp. That is an Ontario Mk III IIRC.
I see what you are saying. Looks like someone tinkered with this one though. Here are a few pics:

https://goo.gl/photos/kb32aNUY7qARfjUz5

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ken123
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Re: Sharpening Recurve on Edge Pro

Post by ken123 » Fri Jun 30, 2017 5:47 pm

As Peter mentions, it isn't usually sharpened but use as more of a blunted edge also giving more support to the tip than if sharpened.

As an alternative but less precise approach, you can use a very slack belt on a belt grinder. (2x72" preferred. There are belts specific for doing this.

A single 6k stone won't work well until you have defined the edge geometry with a coarser grit.

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