KA-BAR USMC, Short; Came dull, cannot get Sharp

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wisnoskij

Joined
Dec 13, 2012
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26
Recently got myself, as a general utility knife, a KA-BAR USMC Short.

This would by my first experience with anything but a stainless steel knife.

It came complexly dull, I know it is supposed to have a wide edge angle but it could cut nothing (so there is no way it was supposed to be like this). my general whetstone seems only capable of marring the black finish, it does not seem to have any effect on the metal. I have some rough tool sharpener, with a rotating stone disk on one end and some rust removing metal brush on the other. This always worked for my other knife (for a rough starting edge), and does at least effect this KA-BAR knife (it seems to be sharpening it, it even seems to actually work at least a little, but then I try to shave wood with it and it completely fails and I touch the edge again it and seems very rounded) The result is that it is still dull enough to stab myself without risk of injury (warm butter is the only material that needs fear cutting by this blade). It is possible I am just doing a bad job, I am a little scared of ruining a brand new knife. I have tried this ?grinder? twice already to no avail.

I am starting to think that something is wrong with the metal. Can anyone explain what might be going wrong. Is there something I am doing wrong, or should I contact the warranty department of KABAR.
 
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The wide edge shouldn't effect the sharpness of the edge and the website says they have a 56-58 HRC, so what ever whetstone you have should be able to sharpen it with no real problems. I would advice staying away from the grinder for now though. That is a good way to over heat the blade by accident and it's better to not have that be an variable while you are trying to get it sharp and working for the first time. For now, i would say get a sharpy and mark the edge to make sure you are apexing the bevel while you sharpen with the whetstone.

After thought, is the black coating on the edge itself? I don't know what they use but it might be abrasive resistant, requiring a bit more work till you get through it initially.
 
You should avoid the grinder wheel unless you really know what you are doing with it.

Most of those small bench grinders spin at either 1500 or 3000 rpm. You can completely ruin the heat treat of the steel with power tools.

(I use a belt sander, which can also ruin the heat treat very quickly). You have to be very careful, keep a dip bucket, and keep the steel cool.
 
No, the black coating stops at the edge.

I was careful with the grinder, I was going for the smallest touch-up, nothing that could heat the blade in the least amount.
 
It wouldn't surprise me if the factory edge angle on the knife is pretty wide (obtuse). Many new large & thick, mass-produced blades come with edges like that, and the 'dull' perception of them is usually the result of a very thick edge angle (wider than 40°, maybe a lot more sometimes). The sharpening and/or grinding you've done so far might've left a burr/wire on the edge which may feel 'sharp' initially and cut a little bit, but will fold over and fail quickly.

If the knife were mine, I'd set about re-bevelling it down to an edge angle that's a little more acute than it likely is now. Anything in the 30-35° inclusive range usually does pretty well (my personal preference would be closer to 30°, perhaps with a tiny microbevel at 35-40°).


David
 
Obsessed with Edges said:
It wouldn't surprise me if the factory edge angle on the knife is pretty wide (obtuse). Many new large & thick, mass-produced blades come with edges like that, and the 'dull' perception of them is usually the result of a very thick edge angle (wider than 40°, maybe a lot more sometimes). The sharpening and/or grinding you've done so far might've left a burr/wire on the edge which may feel 'sharp' initially and cut a little bit, but will fold over and fail quickly.

If the knife were mine, I'd set about re-bevelling it down to an edge angle that's a little more acute than it likely is now. Anything in the 30-35° inclusive range usually does pretty well (my personal preference would be closer to 30°, perhaps with a tiny microbevel at 35-40°).


David
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But if it is easy to ruin a temper when sharpening how would I ever hope to re angle an edge without destroying the metal?
And besides, If I cannot even sharpen this edge I do not think I am capable of redesigning it.


Been trying with the whetstone, still no luck (but I think I am getting better). What I never got about my whetstone is how crumbly it is. Are some types of whetstones suppose to crumple off large portions of dust from themselves when used (large quantities of whetstone dust are created when the blade rubs against it)?
I seemed to only have luck in sharpening when I angled the blade to just scrape off this dust from the whetstone. So I do not think I am digging in, just removing last swipes waste. Or does this sounds completely wrong.
 
And I did try the sharpy trick. It was all rubbed off pretty much right away. I think my problem is partly inconsistency, so it did not really tell my anything.
 
I suggest getting a Lansky, Gatco or Kme sharpener which will control your angles better and you will be pleased. Personally , I use the Gatco with diamond stones and work towards my strop using green Bark River compound. If you can drop the cash for a Wicked Edge or Edgepro they are both well received too.
 
wisnoskij said:
But if it is easy to ruin a temper when sharpening how would I ever hope to re angle an edge without destroying the metal?
And besides, If I cannot even sharpen this edge I do not think I am capable of redesigning it.

And I did try the sharpy trick. It was all rubbed off pretty much right away. I think my problem is partly inconsistency, so it did not really tell my anything
Click to expand...

It's easy to ruin the temper with powered equipment. I think David was implying that you would be re-profiling it by hand on your stone. Personally, getting a guided system of some sort is usually a good idea if you are re-profiling. russianpolander made all the right suggestions.

What kind of whetstone do you have? Are you using a lubricant with it? And are you sure what is coming off is stone and not steel? If it is a softer stone, then you can easily scrape off layers of it while sharpening at too steep an angle.

And for the sharpie thing, are you checking after one or two swipes, or after a lot of passes? You don't have to remove all the sharpie like some people will say. It just helps you know where you are removing metal from and that you are consistently removing it from the same place pass after pass.
 
I am not sure what type it is. two sided, grey, cement/sandstoney.
I know that the fast majority of what is coming of it from the whetstone and for the most part I am not scraping it off with the edge. I normally just add water to it, it soaks it all up and just gets darker in color.

I checked the sharpy mark many times, I did not really notice any pattern (it all disappeared pretty quickly).

I guess I should try one of those guided packages, I have been reluctant until now since I do not need a perfect edge and prefer the idea of being able to duplicate my technique in the field.
 
Yes, my implication was to re-bevel with something other than a powered grinder. No need to risk ruining the temper of the blade by overheating. I think an effective and relatively inexpensive solution, were it me facing the same predicament, would be to use an angle guide, such as a DMT Aligner clamp, and a fairly aggressive bench hone in diamond (C/XC/XXC) or silicon carbide (such as Norton's Crystolon stone). Some coarse-grit wet/dry sandpaper could also work (220/320/400 grit), used on a hard backing like glass, and the paper wetted with water. That could also be used with an angle guide. I recommend a bench-sized hone (or large piece of wet/dry sandpaper) because the work will go more quickly with such a large & thick blade.


David
 
My first thought would be Kabar's Customer Support. Warranty. If it's as bad as you say, send it back and ask for a replacement.
 
If you are looking at guided and want something for the field, then look at the dmt magna guide system. It uses the DMT dia-folds which are great in the field, and cover most of the available grit ranges they offer. You can't go wrong with just that set up. Once the guide gives you a feel for different angles, you can just use the dia-folds. They can just be a little pricey.

ETA: Try soaking your stone in water for a half hour and then see if it still soaks it up when you sharpen. If it does, switch to oil. Mineral works well.
 
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wisnoskij said:
I am not sure what type it is. two sided, grey, cement/sandstoney.
I know that the fast majority of what is coming of it from the whetstone and for the most part I am not scraping it off with the edge. I normally just add water to it, it soaks it all up and just gets darker in color.

I checked the sharpy mark many times, I did not really notice any pattern (it all disappeared pretty quickly).

I guess I should try one of those guided packages, I have been reluctant until now since I do not need a perfect edge and prefer the idea of being able to duplicate my technique in the field.
Click to expand...

Stone description fits Aluminum-Oxide combo type. I've a few of them ($3 variety from Asian grocery store). This stone can completely soak in less than 15 minutes. It could easily abrade 1095 Cryo-van steel, even at upper end of tempered hardness. I frequently use the 60grit side to rub the swarf-outta big blades. caution - watchout for scratches from loose abrasives. Better option - get a $6 Norton Economy SiC stone from Homedepot, teach your USMC some sharp manner!
 
Thanks for all the suggestions, I think my next step will be checking out what is available in some local hardware stores.
 
If in the u.s., home depot is well known around here for carrying a norton SiC combo stone that works very well, Ace sells dmt and smith's, and Dick's sells smith's guided system.
 
fervens said:
If in the u.s., home depot is well known around here for carrying a norton SiC combo stone that works very well, Ace sells dmt and smith's, and Dick's sells smith's guided system.
Click to expand...

The home depot stone is aluminium oxide not silicon carbide.
 
The one i got from my local store looks nothing like my norton india stones, but it looks exactly like the SiC ones you get online. the blueish grey color. I will get a pic of it once i get back to the states. It may be that home depot carries different ones in different regions though.
 
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