Question about sharpening angles.

G

gunguy77

Joined
Dec 18, 2009
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33
Hi Everyone,

I'm hoping someone might suggest the proper way to tackle sharpening a Nata chopper. Is there any way to sharpen this properly on a spyderco sharpmaker? I have stones etc...I'm just trying to figure out the right way to do this. The angle is 17 degrees inclusive.

I appreciate any help

Bobby
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Are you sure it's 17 degrees inclusive? That's a very acute angle, especially for 1095 steel.

If it's 17 degrees per side, you could use the 40 degree inclusive (20 dps) stone angle on your Sharpmaker and put on a small microbevel, that would be a fast and easy way to sharpen and keep sharp.

But with a flat edge and a blade that long, it might be just as easy to sharpen freehand on wide stones. You'd just want to match the angle.
 
Twindog,

Thanks so much for the reply. I was only able to find the diagram above with respect to the angle. The manufacturer is in Japan and the distributor told me "It never needs to be sharpened" which was very disconcerting. I did read one answer to a question on Amazon stating the angle was in fact inclusive and it was 8.5 degrees per side. It clearly cam from the factory with a microbevel and to be honest, I just don't want to foul it up. That said, of course I want to sharpen it. I don't know if seeing the actual item will help you at all, but on Amazon it's the Silky Nata 9.5" Thanks again!
 
I'll go out on a limb and say there's no way that blade is 17 degrees inclusive.

If you have a Sharpmaker at your disposal, wrap a piece of newsprint around the rod in both the 15 degree and 20 degree slots and see if the edge grabs the paper...or...alternatively, slides down on the shoulder. That will give you a start.

Or, you can just mark the edge with a Sharpie and see where the rod makes contact with the bevel.
 
B
Blues said:
I'll go out on a limb and say there's no way that blade is 17 degrees inclusive.

If you have a Sharpmaker at your disposal, wrap a piece of newsprint around the rod in both the 15 degree and 20 degree slots and see if the edge grabs the paper...or...alternatively, slides down on the shoulder. That will give you a start.

Or, you can just mark the edge with a Sharpie and see where the rod makes contact with the bevel.
Click to expand...

Blues,

Thank you. I know this should not be hard, but as someone who tends to overthink everything, it's making me nuts. With the sharpie on the factory microbevel at 40 degrees I'm not really noticing much. I guess at this point the question becomes if I use the sharpmaker as intended, holding the blade straight up and down, I should in theory be sharpening that microbevel.....using the 20 degree per side setting. Does that sound right?
 
gunguy77 said:
Twindog,

Thanks so much for the reply. I was only able to find the diagram above with respect to the angle. The manufacturer is in Japan and the distributor told me "It never needs to be sharpened" which was very disconcerting. I did read one answer to a question on Amazon stating the angle was in fact inclusive and it was 8.5 degrees per side. It clearly cam from the factory with a microbevel and to be honest, I just don't want to foul it up. That said, of course I want to sharpen it. I don't know if seeing the actual item will help you at all, but on Amazon it's the Silky Nata 9.5" Thanks again!
Click to expand...

Your photos don't show up for me. I thought you had the Tops NATA. But now I see it's the Silky NATA 180 mm.

But I looked at the diagram on Amazon. The edge angle is going to be obtuse, which is what you would expect from a "hatchet" used to chop and split wood. You can easily measure the main bevel because it is so wide. The microbevel will be even more obtuse -- no where near 8.5 dps.

The Sharpmaker will work only if the microbevel is 40 degrees inclusive ( 20 dps) or less. I kind of doubt that it is.

Like Blues said, you could paint a small part of the microbevel with a Sharpie and make a light pass with the 40-degree Sharpmaker stone. If no ink is removed and you see a light scratch mark at the shoulder of the microbevel, then the angle of the microbevel will be greater than 40 degrees and the Sharpmaker won't help.

But because it is a microbevel, it will be easy to keep sharp by freehanding on stones -- or with a guided sharpening system that handles obtuse angles.

nata_double_edge.jpg
 
Looking at pics online of the blade, it may be that the wide (scandi-like) primary bevels are ground to 17° inclusive. Scandi-style knives' primary bevels are similarly ground to angles in that ballpark, or very nearly so. But I'm also seeing a narrow secondary bevel behind the edge in the pics, which is no doubt wider in angle and probably something more realistic for a heavy chopping blade. With a tool like a Sharpmaker, I'd just start with the 30° inclusive setting and use a Sharpie to ink the narrow secondary bevels on the blade, to see where it's making contact against the SM's rods.
 
Really appreciate the help everyone. I started in at 20 degrees on the sharpmaker. Guess I should have used the 15 degrees per side instead.
 
Obsessed makes a good point. The primary grind -- could be fairly low. I scaled the knife from photos and data on Silky's site, and the trig shows the primary grind to be about roughly 24 degrees inclusive, but I had to do a lot of estimating. The microbevel will be more obtuse than that.

I'd guess that the 30 degree inclusive (15 dps) Sharpmaker stone would only scratch the shoulders of the edge bevel.

I'd also guess that the microbevel is greater than 20 dps, which means even the 40-degree inclusive Sharpmaker stone won't sharpen it, either.
 
gunguy77 said:
Does this link work for anyone?

https://www.dropbox.com/s/sg0snec7w51w1hl/Screen Shot 2020-04-09 at 11.26.51 AM.png?dl=0
Click to expand...

I'm thinking those two dimensions marked on the drawing ('16.3', '16.5') might be in milimeters(?). If so, it may represent the width of the primary bevel, as those dimensions are pretty wide (16.5 mm is a little more than 5/8-inch). If that's the case, the marked angle (17.0°) seems to refer to the primary bevel grind, as I suspected. The actual sharpening angle should be determined by the angle of the narrower secondary bevel behind the cutting edge, which doesn't seem to be shown in that drawing, from what I can see. Looks like the inset (magnified) representation seems to imply the width of the secondary bevel is 1.0 - 1.5 mm (seems reasonable for a secondary bevel width), but the drawing itself doesn't seem to show the edge angle changing to something wider, in that portion.
 
The diagram shows that Obsessed was correct about the claimed 17 degrees inclusive angle for the primary bevel. But that's not the angle you would sharpen at because there is a microbevel, which will be more obtuse than the primary bevel.

The diagram doesn't say what angle the microbevel is set at. It's also confusing because in the top diagram it says the vertical width of the microbevel is 2 mm. The lower diagram says it's 1 mm, plus or minus .5 mm.

When I do the trigonometry using these numbers, the angle of the primary bevel calculates to 20 degrees inclusive. I can't calculate the angle of the microbevel with just the data given, but it will be more than 20 degrees inclusive. I'd guess it would be more than 40 degrees inclusive.

If you sharpen the knife with a few strokes at the 40-degree Sharpmaker setting, you will raise a small burr if the angle of the microbevel is more acute (less than) than 40 degrees. If no burr appears, the angle of the microbevel will be greater than 40 degrees. In that case, you'll just be rounding off the shoulders of the microbevel.
 
Gentlemen,

First thank you both for being so helpful. I hit it on the sharpmaker this time at the 15 degree per side angles. Functionally, it seems to work just fine. Then again, it seemed to work just fine when it arrived. Nonetheless, I had to fiddle with it. So I guess from here on, it's 15 degrees per side on the sharpmaker until I am confident enough to use a bench stone.

Having said all this, would you suggest A. using the 15 or B. starting from scratch and using the 20 degree per side on the sharpmaker. C. back away and never touch anything knife or edge related again.
 
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gunguy77 said:
Gentlemen,

First thank you both for being so helpful. I hit it on the sharpmaker this time at the 15 degree per side angles. Functionally, it seems to work just fine. Then again, it seemed to work just fine when it arrived. Nonetheless, I had to fiddle with it. So I guess from here on, it's 15 degrees per side on the sharpmaker until I am confident enough to use a bench stone.

Having said all this, would you suggest A. using the 15 or B. starting from scratch and using the 20 degree per side on the sharpmaker. C. back away and never touch anything knife or edge related again.
Click to expand...

I would use the 40-degree inclusive (20 dps) set up on the Sharpmaker. If stones set at the 30-degree-inclusive angle sharpen the edge (which I doubt), the 40 degree inclusive will, too; and the 40-degree setting will give you a more robust edge, consistent with the function of a chopper.
 
I asked them.
They said that the angle is 40 for chisel and 60 for double edge on their current models.
The edge angles used to be lower but increased per users' requests.
 
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