Relief Grind Performance

I had an interesting thing happen to me today. A while ago, I had reground my Leatherman Surge Plain Blade with my HB 1x30 belt grinder. I was needing to open a package today, and instead of grabbing my trusty Spyderco Siren, I grabbed the LM Surge as it was easier to access, because the Siren was being carried in its normal spot, right side IWB. The LM Surge Plain Blade, because it had been reground, floated through the tape and into the cardboard effortlessly. Now because I haven't reground the Siren, it wouldn't have cut the package so easily, simply due to the geometry of the blade. I kept it stock, other than a sharpening because I wanted to have a knife on my that wasn't reground and could stand up to more abuse and harder cutting jobs. I learned this carry method from Cliff, to carry one reground knife for light and medium cutting, and a stock blade with a thicker grind for more heavy cutting jobs. What surprised me was how effortlessly the knife went through the material. I couldn't tell the difference between when the LM Surge Plain Blade was cutting the tape or the cardboard. That shocked me. No matter how sharp I make the Siren, and I gave it a good sharpening on a fixed angle system, it just won't cut as effortlessly as the lesser steel (420HC) and heat-treated knife (LM HT isn't known for being great). Now, this really hurt my feelings, as the Spyderco Siren is an awesome knife all the way around: design, materials, heat treatment. The first thing that I thought of was to regrind the Spyderco Siren, but that would defeat the purpose of the carry method I was using, and its purpose in that system, as well as the fact that I wanted to have a knife that was still attractive. Fort some reason, a lot of people care more about how the knife looks than if it actually cuts well. Anyway, I think I am going to buy a different Spyderco Siren and regrind it. It won't look great, as I am not the best blade grinder, but I am sure that thing would cut like crazy thinned out. So it might not look perfect. Oh well, that is what I would have the other Siren for. Time to start saving my money. I would highly suggest a regrind for people who want knives to cut well. And I mean CUT well, as you can barely feel like you are cutting anything.

it would definitely be a performer if thinned out.
im actually keeping mine fairly close to stock. i did thin it a little when cleaning it up..

but as a bait and fillet knife, that secondary edge can be good for removing the skin without being so lean it bites into the skin too easily

I had a similar experience recently.

I don't use production knives that I haven't reground to be thinner, but even still, going even thinner made a surprising difference. For example, my hap 40 endura is sitting at 7dps 0.013-0.015" thick, and compared to that my 6dps 0.005" power hacksaw blade knife goes through cardboard like it isn't even there.

Well, this is embarrassing. Turns out the Spyderco Siren wasn't sharp. After a quick stropping, it cut a lot better, just started to bind a bit, about 0.5" into the cardboard. Otherwise, it sliced straight through the tape and into the cardboard, so the performance of the sharp blade was a lot better than first reported.

It definitely makes a huge difference.

On almost every flat ground blade I own I’ve blended the primary into the secondary with a shallow convex to increase performance and reduce drag, I then add a micro. It might not look great to some people but it definitely works very well and I like it. Over time, the convex blended portion will become larger until the primary needs some thinning out. Keep it shallow and it still cuts very well.

The only two Flat ground knives I haven’t done this to (I don’t own a ton of flat ground blades…about 14 or so and at least a dozen of them are folders) are my Maxamet Native 5 and PM2 and I’m not particularly interested in doing that on those due to the time it would take (by hand). Sure, it wouldn’t take that much longer than S110V (which I’ve done numerous times) or similar on Diamond abrasives but even reprofiling that steel by hand annoys me these days. I really enjoy experimenting with these “Duper steels” but I actually prefer simple carbon steels like 1070, 1080, 1095, 01, 52100, etc; and in stainless I like the 440 class, 12C27 etc.

For major reprofiling I really need to get a small belt grinder (2” would be great) as I don’t have the patience to do it on stones/plates anymore. I still have a couple of large fixed blades laying around with half to 3/4 reground bevels done by hand due to losing the motivation and patience to finish them. Sharpening is enjoyable to me, major reprofiling without belts isn’t.

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Wolfgang
I really enjoy experimenting with these “Duper steels” but I actually prefer simple carbon steels like 1070, 1080, 1095, 01, 52100, etc; and in stainless I like the 440 class, 12C27 etc.

For major reprofiling I really need to get a small belt grinder (2” would be great) as I don’t have the patience to do it on stones/plates anymore. I still have a couple of large fixed blades laying around with half to 3/4 reground bevels done by hand due to losing the motivation and patience to finish them. Sharpening is enjoyable to me, major reprofiling without belts isn’t.

Yeah, I prefer the Class I and Class II steels myself also. I also don't like doing relief grinds by hand anymore, although an XC Crystolon or XXC Venev Diamond Waterstone make short work of it if I am in the mood or don't feel like using the 1x30".

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jasonstone20

I really enjoy experimenting with these “Duper steels” but I actually prefer simple carbon steels like 1070, 1080, 1095, 01, 52100, etc; and in stainless I like the 440 class, 12C27 etc.

For major reprofiling I really need to get a small belt grinder (2” would be great) as I don’t have the patience to do it on stones/plates anymore. I still have a couple of large fixed blades laying around with half to 3/4 reground bevels done by hand due to losing the motivation and patience to finish them. Sharpening is enjoyable to me, major reprofiling without belts isn’t.


Yeah, I prefer the Class I and Class II steels myself also. I also don't like doing relief grinds by hand anymore, although an XC Crystolon or XXC Venev Diamond Waterstone make short work of it if I am in the mood or don't feel like using the 1x30".

After thinking about this yesterday I decided to reprofile the Native 5 Maxamet by hand anyways. I used a cheap* Diamond steel of about #500 with an oval cross section to decrease the contact point and thus abraid faster. It really took me no longer than S110V on an Atoma #140. I blended the apex into the primary in a shallow convex and then micro beveled.

It cuts much better with far less resistance.

* and I do mean cheap. When I got it given to me it had been used for years, stored poorly in Saltwater conditions, never cleaned, and had rust spots near the handle. It done very well with Maxamet, surprisingly.

Wolfgang,
Nice! I have only sharpened Maxamet once, on diamond waterstones.

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jasonstone20
Wolfgang,
Nice! I have only sharpened Maxamet once, on diamond waterstones.

How did you find it? Any issues setting the apex?

I don’t have any Diamond waterstones but will likely get at least one, possibly the Naniwa Diamond #800 just for apexing.

With my first few apex sets I just wasn’t happy with the results. Rather than blame the steel I blamed myself and asked “what am I doing wrong? / what am I missing?”

I finally realized it was due to the V edge, which I was trying to keep, as I can never get those how I like them regardless of steel and so I always thin the secondary down into the primary to accept a 10-12° micro bevel. It seems just fine so far. My sharpening techniques always want to convex the blades (except scandi grinds) and so I just roll with it.

I like the idea of hard steels but I’m not really a big fan of high carbide steels (>22%) like this. I put off buying Maxamet for a few years but it got the better of me. I love experimenting with stuff.

Wolfgang,

No issues at all. It was Shawn Houston/Triple B/Big Brown Bear's knife, we met at a local knife store that is right up the street from my house, and he had some of the guys there show me a bunch of sharpening stones. The knife was a Spyderco Manix 2, and I think the reason I had such an easy time sharpening it (not only because I was using the correct abrasive) was that it had been sharpened quite a few times before. Often on factory knives the edge is burnt, and even more so with Maxamet, even though Spyderco takes precautions for this not to happen, it unfortunately still does, it is just a side effect of mass production.

Sharpening edges can be a deeper rabbit hole than most would imagine.

sal

I see a market for a purpose built scale to set stones on to easily see pressure. One of you entrepreneurs care to sharpen you pencil? I'll buy the first 2.

sal

sal,
That is a good idea. Maybe also a 3d printed tray to hold stones so you can use any scale. Pressure is definitely one of the things that doesn't get talked about a lot when it comes to sharpening.



PS I have a copy of the old forum on a USB Thumb drive that I can send you. If you could email/DM me a mailing address, and I can send it to you.

Hi Jason,

I'm at;

Spyderco
Attn: Sal Glesser
820 Spyderco Way
Golden, Colorado 80403

Thanx much.

sal

Knife thinning takes so much effort but it's key to great performance.
Knife geometry can be quite tricky and understanding what we are doing can save a lot of time.

Full flat grind looks amazing because knife gets so thin but often its not the best cutting performance because of food adhesion.

Convex grind usually is thicker but it reduce food adhesion and cutting resistance. There is always a balance, an obvious thick convex grind will stick less to food but will create a shoulder and reduce cutting capacity.

Best performance I got is from what I call a hidden convex. It looks flat but if you put a ruler on side you can see there is a slight convex.
This saves a huge amount of time because doing hidden convex is a lot faster than creating a Full Flat V zero on stone.

Ruler and caliper really help understanding how geometry affects knife performance and then setting goals for future thinning.

Thiago,
I think you are right about the hidden convex grind. Kylie Harris, when he made knives, used to make a thin convex that thicked about 5-10 mm or 0.5" from the edge to give the knife both cutting performance and strength. He can explain it better than I can. I think if you can find one, you might like a full-height hollow grind.

Many Japanese knife makers do Hollow grind on those large stone wheels. I didn't mention it because Its not a viable geometry plan for us sharpening on straight stones but I bet they cut great.

Living in Brazil kind of limits our options. A 60 dollars Kuromaku stone gets taxed so high it costs one month working on minimum wage, five days a week. A hand sharpened Japanese knife on good steel would cost a small fortune, lol.

Thiago,
What knives are available to you? I think Tramotina is made in Brazil, they make good knives and awesome machetes. I only have 2 or 3 knives that have a full height hollow myself, and those are small knives, >3".

Japan decided to stop shipping standard air mail to Brazil so anything from them applies much higher taxes than Chinese brands. Double tax from Japan for no reason really pisses me off.

I got some Brazillian brands like Tramontina,Brinox and Corneta. Also got several Chinese knives. Xinzuo, Shibazi, Xituo, Dongsun and others.


Most of them work fine but don't have same cutting performance on hard vegetables as a Japanese knife or even a well made European blade. The issue that bothers me is not steel type or heat treatment. They just don't pay enough attention to geometry and I need to fix it myself.
Well... most of them don't. Xituo Butcher is one exception and has great overall geometry. It passes well the onion Brunoise test which is quite tough for bad geometry knives.

I got a review on my Yt channel if you want to watch. Its on Portuguese so probably not that helpful but at least cutting performance speaks for itself. My review is with factory edge without any modification.





I modified its edge geometry this week, changed the edge angle to 8° with 15° microbevel and will test it out soon. I bet its better than the original with the light modification.

Another exception is Shibazi F208-2. Quite good cutting performance after edge angle modification. Also got a review on it. Its a vegetable cleaver so not for everyone but I do enjoy it.

Also got one made by a friend knife maker. I just received and haven’t tested it yet but I already know geometry is a beast, probably one of the best knives I own.

Thiago,
Nice! I will check out your YouTube. Maybe auto translate will work on the videos. Can you get American Knives or European knives easily? There are some companies and makers that make Japanese style knives

Usually there is a shipping issue. Importing from Brazil is a pain but I would be glad to check them out. What are your brand recommendations?

Just so you have an idea. I've been recommended Victorinox Fibrox as a good cheap knife. It reaches Brazil for half a month working on minimum wage. Its just stupid expensive here. For that exact same price I can buy a Gyuto 14C28N 60HRC with ebony handle even tho actual price is double the Fibrox. The custom build knife I got from a knife maker, made with electic oven, was cheaper than the Fibrox. It's crazy.

Brazil tax and enxchage is no joke but I do want to know your recommendations.

Thiago,
Victorinox was going to be one of my recommendations, as well as Heder Windmill knives. How much would it cost if I bought one in the USA for you and sent it to Brazil as a gift? Would there still be taxes and import duties and the like?

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Thiago

Living in Brazil kind of limits our options. A 60 dollars Kuromaku stone gets taxed so high it costs one month working on minimum wage, five days a week. A hand sharpened Japanese knife on good steel would cost a small fortune, lol.

Oi,Thiago

Tudo bem?

We could probably work something out to benefit both of us regarding stones. It would of course depend on costs and shipping etc and avoiding the taxman as much as possible for both of us.

Meaning: getting you some Shaptons in whatever grits you want and me getting some pedras de Carborundum Alta Gastronomia series which I’d like to try out.

Australia likes to screw people over with taxes just like Brasil.


If you’re interested in talking about it PM me and we’ll exchange emails.