edge retention question

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Apr 3, 2014
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587
Hello Fellow knife enthusiasts,

I was wondering if any edge retention experts could weigh in on this.
I have many knives and many different steels.
I own a landscaping business, so Im out in the field working most days, which means I get to use my knives a lot.

I see edge retention tests using ropes for the cutting materials and how long it takes to wear down an edge cutting rope.

I need a knife steel that can last as long cutting open bags of grass clipping as they all last cutting rope, haha.

I want to know what you guys think it is that trashes the sharpness of my edges so fast.
They are the basic costco Black outdoor garbage bags, the plastic ones. We fill them with just grass clippings, thats it.

Doesnt matter the steel, D2, M390, 1095, S35VN, M4, etc, etc, etc.
I can start with a fresh newly sharpened edge on any of them, and they all get dull by maybe the 5th or 6th bag of cutting open the bottoms.
The first 4 or 5 bags slice open like a hot knife through butter, then around bag 6 or 7, no more slicey slicey, they rip and tear more than slice.

Is the plastic the abrasive part, or the grass clippings?
Are grass clipping some super material that we dont know of? lol. And thats why a lawnmower blade can go dull after a week. lol

What do you think?

Im not asking for suggestions for a new knife, or a new type of knife, or that I need a utility razor blade, or a new sharpener or any of that.
Just wanted opinions on why plastic and/or grass clippings are so abrasive.

Thanks
 
I would guess that at the end of the day the dirt and heavier debris settles to the bottom of the bag and you are cutting into that which causes your edge to dull quickly.
The other part to that is having a wire edge which feels sharp but will dull quickly making you believe most steels won’t hold an edge very long. It’s happened to me.
 
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Neither plastic nor plant material should present that much wear. I'd also put my money on dirt. Dirt can have a lot of grit. That's why I wince whenever I see someone stick their sword into the ground on TV.

Maybe the sharpening gurus will have something helpful to add. How sharp are you starting and what exactly do you mean by "dull"?
 
I Don't know what makes it so. But my experience cutting open plastic bag of frozen food, suggests that plastic is pretty abrasive stuff. It has a very similar effect on a sharp blade as cardboard does .

O.B.
 
M morvlorv
Please forgive the asking.
Decades ago I had a lawn maintenance and tree trimming/removal business. I've also done yard and beach maintenance, and (coco nut tree) tree trimming (among other things) as part of my duties as property manager for a vacation rental home, in the Florida Keys.
Based on the several decades experience in that field, I have to ask:
"Why are you opening (from the bottom, top, or side, or any combination thereof) the bags of grass clippings, and leaf remains/rakings, after binding or tying them closed?"
 
Hello Fellow knife enthusiasts,

I was wondering if any edge retention experts could weigh in on this.
I have many knives and many different steels.
I own a landscaping business, so Im out in the field working most days, which means I get to use my knives a lot.

I see edge retention tests using ropes for the cutting materials and how long it takes to wear down an edge cutting rope.

I need a knife steel that can last as long cutting open bags of grass clipping as they all last cutting rope, haha.

I want to know what you guys think it is that trashes the sharpness of my edges so fast.
They are the basic costco Black outdoor garbage bags, the plastic ones. We fill them with just grass clippings, thats it.

Doesnt matter the steel, D2, M390, 1095, S35VN, M4, etc, etc, etc.
I can start with a fresh newly sharpened edge on any of them, and they all get dull by maybe the 5th or 6th bag of cutting open the bottoms.
The first 4 or 5 bags slice open like a hot knife through butter, then around bag 6 or 7, no more slicey slicey, they rip and tear more than slice.

Is the plastic the abrasive part, or the grass clippings?
Are grass clipping some super material that we dont know of? lol. And thats why a lawnmower blade can go dull after a week. lol

What do you think?

Im not asking for suggestions for a new knife, or a new type of knife, or that I need a utility razor blade, or a new sharpener or any of that.
Just wanted opinions on why plastic and/or grass clippings are so abrasive.

Thanks

When I worked in commercial/industrial landscaping, to include a large nursery from half gallon pots to 30' trees, it was...Utility knife, hand trowel (often with a sharpened edge) and sheers.

I know you said you're not asking for suggestions, but rather what the abrasives are, but they aren't mutually exclusive. Everything you're dealing with is abrasive. Dirt is terrible on edges. No steel is going to fair well for long in those conditions.

We'd mostly stab a bag of (fill in the blank) and tear it open or stab it all the away across with our trowel as anything. The little trowels did the heavy lifting.
 
You wouldn't think it, but a little bit of dirt will dull almost any blade as quickly as a ceramic plate. Happened when I used my 562cf to cut some weeds. Dulled the crap out of it. Cut a sandwich on a plate once. Dulled the crap out of it. Just have to be care what your edge hits.
 
Just get a serrated Spyderco Pacific Salt. Sharpen it with a Sharpmaker's medium rods or a diamond rod (probably one that tapers) that's narrow enough to get in the small serration scallops.
 
My advise. Get a Salt SE.

It would out last most of the other steels.

I have been using my SE Atlantic salt for years in the oil and gas industry cutting everything. Heavily modified by now to suit my needs.
 
Okay before I begin, I'm cheap. It comes from my Scottish ancestors.

I would suggest that you get a handful of utility knives next time you are at the hardware store. They are great for stuff like cutting open plastic fertilizer bags, etc. Get dull, you break off the old piece and voila! you have a new sharp blade. You can do this many times before you need a new utility knife. I don't know what the steel type it is but who cares. Cheap, cuts well, light in the pocket, cut tons of times, etc. For those who are not in the trades or home hobbyists, here is how they work. Just don't cut yourself. I take no responsibility for that.


 
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I'm similar to you in that I find the more premium steels pretty much worthless for actual work. Softer steel is far superior when actually getting them dirty because you can get them razor sharp again as and when you need in a few seconds, unlike any of the steel you listed, plus they're tougher due to the softer material and the harder steels chip far too easily and can be prohibitively expensive to replace when you inevitably need to - far faster than with a cheap steel like 440c, Aus8, 8cr13mov and so on I might add.

Simply put, avoid the pocket jewelry and overpriced tacticool and get a cheap knife from a dependable manufacturer like Kershaw or Byrd that you don't have to baby.

Also don't sharpen softer steel to the usual 40 degree bevel, aim for 30 with a 15 degree bevel on either side, preferably with a ceramic rod. Longer wearing edge by a mile, but harder steels just chip even worse with this edge geometry.
 
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It's probably the grass. Many grasses are EXTREMELY abrasive, even if the grass is clean and free of other debris. Many animals that eat grass have teeth that grow for the duration of their lifetime and grass wears their teeth down. When these animals are kept in captivity and not fed proper grasses accordingly, their teeth can grow absolutely out of control and yield an end result that looks like a monster movie. (Rabbit teeth grow about 4-ish inches a year.)

I am not a steel expert, but steels containing crap tons of vanadium carbides are going to likely fare the best specifically against the grass, and your particular usage situation would likely see a huge real-world difference between K390 and M390, for example, whereas someone cutting materials not so abrasive might not see nearly as pronounced a difference between the two steels.
 
Doesnt matter the steel, D2, M390, 1095, S35VN, M4, etc, etc, etc.
I can start with a fresh newly sharpened edge on any of them, and they all get dull by maybe the 5th or 6th bag of cutting open the bottoms.
The first 4 or 5 bags slice open like a hot knife through butter, then around bag 6 or 7, no more slicey slicey, they rip and tear more than slice.


What do you think?
Well , I think that something is wrong with your knives . If any of my knives don t slice open at least hundreds of that bags I will EAT that knife !!
 
You wouldn't think it, but a little bit of dirt will dull almost any blade as quickly as a ceramic plate. Happened when I used my 562cf to cut some weeds. Dulled the crap out of it. Cut a sandwich on a plate once. Dulled the crap out of it. Just have to be care what your edge hits.
I trying to imagine how that would work but I can t ? Dirt is not fixed to anything inside that bag .It will move away from edge ...that is EASY way for dirt to do .On grass ? So we have some very very fine dust /say it is sand / on grass and we cut that grass with knife.....how that dust can stay right on the way of edge to dull knife in slow motion of edge ? Rubbing on sides of edge ??? I don t get it , really !Fast moving lawnmower blade ..maybe !
 
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