Long term carbide scraper use

:barf: Blade scrapers... Edge eaters.. They are only good for quickly thinning the edges of some lawn and garden tools and even then there are better tools for the job. Stay away from blade scrapers!! :)
 
gpdawg said:
if you use oil and not press down to hard the carbide V sharpeners work just fine.
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The problem is you must use force for the scraper to work and to add oil is not going to change the result of the edge. If you want to use it then that's your choice but I would advise changing your method before too much damage is caused to your blade.
 
Well, since you went through all that and took those nice pictures you might as well try it with oil. Again, in the interest of science.

That's sick. I can't believe I read this whole thread.
 
dtmc said:
I found a nice V shape carbide sharpener, and after years of freehand sharpening, I am experimenting with this on some of my Wife's cheap kitchen knives. I am using it to quickly remove the "shoulders" from these really dull edges, basically re-shaping the blade quickly. Then I go on with a DMT diamond hone, and a ceramic to clean up the edge. I get pretty good results in about 3-5 minutes. PS, my wife doesn't want her knives too sharp. She learned how to use dull knives when she was growing up. She cuts herself if I sharpen her knives to my standards.

I feel a little guilty as I see the steel peeling away, but it's a faster way to remove the shoulders from one of her dead kitchen knives so I can move on to the sharpening process. I feel like I would have to remove this material anyway, this is just much faster that my diamond hone.

Comments???
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This is pretty much how I start the edges on new knives coming off the bench. It's a lot faster that way. You end up learning how nto not divot up the edge (too badly) so that you can finish up with a rough ceramic, then fine ceramic stone.

Jim L.
 
Just saved those pics that knifenut posted, plan on using them to show a friend why they are so bad.
 
knifenut1013 said:
That thing that looks like a thumb stud is the metal shavings produced by the scraper :eek:
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Looking closely at that chunk of metal that was removed from the blade it looks to me like three may have been an inclusion in the steel. Was this low quality steel? I'm not defending the carbide V tool, just saying.

BTW, I realize I'm resurrecting a 12 month old thread. It just validates that what you guys/gals are posting is helpful. God bless the Internet.
 
It's just how the scrapper works, it scrapes a large volume of metal off the blade and the more you use it the more it tends to chatter and create that jagged looking result.

You wouldn't be able to see a inclusion with the naked eye anyways, you would need a SEM.
 
It's truly a shame that so many owners of sporting goods stores, who should know better, allow those things to be sold in their stores.

I've restored quite a few knives that were damaged by these things for good friends and colleagues.

My only "fee" that I charge for a repair is that I must be allowed to witness them throwing the damnable thing in the dumpster.

My advice to them is simply that if they do not know how to sharpen, and have no desire to learn, have someone else sharpen for them.
 
knifenut1013 said:
You wouldn't be able to see a inclusion with the naked eye anyways, you would need a SEM.
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Knifenut, I suspect you've forgotten more about knives and metallurgy than I will ever know, so please correct me. What I meant was that an inclusion or impurity in the steel caused that part of the blade to be weak and to break off like that. I'm asking because there is a difference (in my mind) between roughing up an edge horribly and ripping chunks out of it. Could it have been the steel?
 
The steel gets 'ripped' like that, due to the thin & fragile edge being pinched as it's drawn through the scraper inserts. Compare to doing the same with an index (recipe) card, drawn through a pair of scissors opened to a similar 'V', and oriented vertically in the same fashion as the scraper. The hard and very crisp edges of the scissors will dig into the thin edge of the card with the slightest of downward pressure, which effectively pinches it and keeps it from slipping smoothly through the 'V'. Pulling it through will leave the edge of the card in tatters, as the edge of the card alternately gets pinched, ripped loose, pinched and ripped loose again (that's the 'chattering' effect described before). Softer (weaker) steels will be more easily pinched like this, therefore more damage done to an edge. Very hard steels would more likely be prone to chipping at the edge, from the extreme focused pressure of the scraper's edges against a very small portion of the blade's edge.

Even if the steel was weakened by inclusions or whatever, the same defect would likely go completely unnoticed when sharpened by most other methods, as the blade edge wouldn't be subjected to the same 'pinching' effect. That's what does the real damage, with these scraper-type sharpeners; it's just the way the tool is set up, like a pair of scissors.


David
 
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No, the steel did not break off it was ripped off by the scrapper.Very well put, David.
 
Obsessed with Edges said:
Thanks! :thumbup:

(the index card 'test' with scissors is an eye-opener, if one tries it for real; the similarities in damage done are scary. :eek: )


David
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Readin your description, I was wondering if you tried the card test ... I guessed right ;)

Your explanation on the pinching and tatters is crystal clear! :thumbup:
 
Dr.X said:
Certainly makes sense. Wouldn't oil reduce this?
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Maybe somewhat. But the scissor-like configuration still subjects the edge to sharply-focused pinching pressure, even before the stroke begins, which increases the risk of ripping/tearing damage that wouldn't occur at all with other sharpening methods. I'd bet using it with oil would contribute more to a false sense of security more often than not.

The greater risk comes from the two very hard and very sharp edges of the carbide inserts exerting pinpoint pressure from opposite sides of the edge at the same time, which is why it's so easy to pinch and damage the edge. Even more so, as the edge gets thinner and more delicate.


David
 
Ouch...

when I see someone with one (scraper) I ask if I can throw it away and offer them a free sharpening.
 
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