Sharpening a Tina Knife

A Tina document on the web says its knives should be sharpened to a 5 degree angle. I’ve never seen such an acute angle recommended for any knife for any application. Most sharpening jigs will not sharpen at angles of less than 15 degrees. And I’ve seen recommendation here that knives should not be sharpened at less than a 15 degree angle, otherwise the edge dulls too quickly. Does anyone sharpen their Tina knife to a 5 degree angle? If not, what angles do you use?

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I use 15. That 5 must be typo. Do you have link to it?

edit: I don’t know what I was thinking. I sharpen my hard steel Japanese kitchen knives to 15 degrees. My Tina grafting knife is beveled on just one side and I use 25 degrees (equivalent to 12.5 on each side of a double bevel). My other grafting knives I do to 30 degrees single bevel.

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Here is the link. https://www.tina-messerfabrik.de/files/Sharpening%20TINA%20Horticultural%20Knives.pdf

I have a Tina knife that I sharpened to a very narrow angle , maybe 5 or 10 deg.
The edge curled when attempting cuts .
Rebeveled to around 15 deg. ,that works .

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I don’t think it is a typo. It makes sense as the smaller the angle the cleaner the cut. Of course more sharpening will be needed. I switched to a smaller angle for my kitchen knives a few years ago and yes I am sharpening more but no I will never go back … the knives just work so much better.

I sharpen my Tina knife with a stone, and don’t actually know the angle. It’s fairly narrow, though.

Scott, 5 degrees would be extreme. I don’t think I’ve seen a knife sharpened that shallow. I don’t think it would be useful as a knife.

It may be useful for the flat side of the blade if grinding the whole flat would remove to much metal or take too long.

I was an oboe player and reed maker for many years and some reed knives are less than 10 degrees. Razor blades are less than 10 degrees.

I do wonder a bit about 5 degrees though as that is indeed a very low number. Maybe they were thinking of a knife with two bevels so 5 degrees on each side, then forgot to double for a single bevel knife. Or maybe they are in fact doing something like 7-8 degrees and called that “about 5 degrees”.

The linked document says 5 degrees for both the one side and both side bevels. So the included angle on the double would be 10. But they don’t ship the knives like that and nobody uses them that way. Not even close.

OK it sounds like they have at least one typo as I don’t think they meant the one-side bevel to be half the overall angle of the two-side one… still I think 10 degrees is sensible. I used a knife about that angle in the past and found it cut very cleanly. I am tempted to sharpen one of my Victorinox knives to 10 degrees and see how it does.

I await your report.

You asked for it you got it :grinning:

Well I admit I had a reason to try it out, I am grafting tomatoes now and last year I used my grafting knife and it was not slicing through as well as I had hoped so I was going to use a razor blade this year to get the narrower angle. Then I remembered this post… so I grabbed one of my Victorinox knives and sharpened it to around 10 degrees.

The biggest problem I had was the flat side was not completely flat and I needed so spend a lot of time with a coarse stone getting it flat. You really need to have the flat side totally flat if you are going to get all of the burrs off with such a narrow angle. It was also challenging holding the blade fixed at the angle. The previous knives I sharpened at narrow angles were wedges, flat on both sides, so they were easy to sharpen exactly to the right angle. Anyway in the end I got it sharp and it worked well on the tomatoes. I can see how this could be challenging though.

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That was fast.

I did some actual fruit tree grafts today with my 10° Victorinox.

The first lesson is: watch out!! That thing is going to cut you when you don’t even realize it. I got a gusher on my middle finger and I barely touched the knife.

For grafting, the 10° angle is definitely better, once I got used to it I was making cleaner more accurate cuts. It cuts differently so it takes a bit of getting used to. It was particularly nice for cleft grafts, it was easier to get the knife in the wood to make the cleft. It was also more accurate on chip bud cutting.

It is too bad it is so hard to sharpen and is an added degree of danger. It will also need more frequent re-sharpening. So, like everything else it is a trade-off. I have two knives and I am going to keep this one at 10° for the foreseeable future.

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I sharpened my Tina knife to 10 degrees this year. I had the same problem as Scott, flattening the flat edge. But eventually I achieved something close to 10 degrees.

Compared to previous years (when I had a 15 degree edge), the knife cuts better. That may be attributable to the sharpening method. In the past I used a sharpening jig (wicked edge). This year, I used Japanese water stones. But 10 degrees on Japanese water stones works great.

I don’t sense that the edge is dulling quickly. I’ve done about 50 grafts, and I see no change in cutting efficacy. But I have used a sharpening steel several times to make sure the edge is straight.

In sum, I like the 10 degree edge. That’s what I will use going forward.

I should add that I sent an email to Tina inquiring about their 5 degree document. I got no response.

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This is 10 degrees inclusive, beveled only on one side? I thought my 25 degrees was pretty aggressive. I may need to go further.

Right, the overall angle is 10 degrees and it is all on the bevel, the other side is completely flat. I don’t know if it is exactly 10 degrees but the bevel face looks to be about twice as long as on my other knife so it should be about half the angle of that one.