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How to repair or minimize blade chip?
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I have a problem that I don't know how to minimize or mitigate, a small chip. The blade is three-layer laminated Cowry X Damascus steel -- cutting edge is homogenous Cowry X steel; outer laminations are Damascus AISI 420.

What do I do to reduce the size and abruptness of the chip relative to the remainder of the blade?


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Posts: 1443 | Location: Seeley Lake | Registered: 21 November 2007Reply With Quote
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I neglected to mention that the blade has convex grind.


It's so simple to be wise. Just think of something stupid to say and then don't say it. Sam Levinson
 
Posts: 1443 | Location: Seeley Lake | Registered: 21 November 2007Reply With Quote
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Get the maker to resharpen it till the chipped out place is gone.



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Posts: 8279 | Location: Jennings Louisiana, Arkansas by way of Alabama by way of South Carloina by way of County Antrim Irland by way of Lanarkshire Scotland. | Registered: 02 November 2001Reply With Quote
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I want to do the job myself. . . .

Were the edge sharpened until the nick disappears, we're talking about, perhaps .125 inch of metal along the entire edge?? Is there an alternative that moves metal more localized?


It's so simple to be wise. Just think of something stupid to say and then don't say it. Sam Levinson
 
Posts: 1443 | Location: Seeley Lake | Registered: 21 November 2007Reply With Quote
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Good heavens! An 1/8" of metal removal to take out the nick? That blade must be just huge!

(Actually I don't think it will require that much at all. Looks like the width of the sharpened area is maybe 0.020" or so.

My concern is that to get such a chip you either hit the edge pretty hard, or the HT is too hard and the blade is brittle. If it is a brittleness problem chips will likely reappear.

The smith needs to see the damage or at very least the pictures of the damage along with an explanation of how it was achieved. He should probably fix it too. One way to help this problem might be to re-sharpen the knife with a less severe sharpening angle so that the edge is better supported. Probably won't feel as sharp or sharpen as easily though.

BTW I am a damascus steel and knife maker.


Mike

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DRSS, Womper's Club, NRA Life Member/Charter Member NRA Golden Eagles ...
Knifemaker, http://www.mstarling.com
 
Posts: 6199 | Location: Charleston, WV | Registered: 31 August 2002Reply With Quote
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quote:
Originally posted by mstarling:
An 1/8" of metal removal to take out the nick? That blade must be just huge!

(Actually I don't think it will require that much at all. Looks like the width of the sharpened area is maybe 0.020" or so.

My concern is that to get such a chip you either hit the edge pretty hard, or the HT is too hard and the blade is brittle. If it is a brittleness problem chips will likely reappear. One way to help this problem might be to re-sharpen the knife with a less severe sharpening angle so that the edge is better supported. Probably won't feel as sharp or sharpen as easily though.

BTW I am a damascus steel and knife maker.
Many thanks for the information. I wrote unclearly. The approximate length of chip is .125 inch. Its depth is significantly less. Without attempting to measure it, your estimate of .020 may be correct.

Regarding sharpening angle of bevel, I am practicing stropping-to-sharpen on another blade. To move metal to reduce the entire edge to conform with lowest part of the chip is something I prefer to avoid -- if I can regularize chip's boundaries. I envision a process similar to what millwrights used to do on chipped saw blades. They would grind away the problem area to a nearly circular shape. Circular is too much, probably. But altering the profile to gentle slopes?? Is something like that doable? If we assume the chip has nothing to do with brittleness would that be a satisfactory solution?

Cowry X, may be more brittle than many steels because of its HRC range of 63-65. Probably, that's the reason for laminating it between 420 -- similar to Harry Morseth's Brusletto blades.



It's so simple to be wise. Just think of something stupid to say and then don't say it. Sam Levinson
 
Posts: 1443 | Location: Seeley Lake | Registered: 21 November 2007Reply With Quote
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If you want to try that, I'd suggest using a round medium india stone about 1/2" in diameter along with a 1/2" square india stone. You can probably make the existing chip almost disappear.

That will not, however, do anything for the blade's tendency to chip because it is too hard.

Almost all materials can be HT'd to values lower than the initial hardness from the quench step. Is done by heating the material to 400 or so for an hour, testing the hardness, and doing it again and again if necessary. The smith needs to know he went too hard. Enough feedback may convince him that he needs to do this.

The San Mai construction is designed to provide a hard material embedded in a body of more flexible material. Doesn't mean that one should get the hard material too hard! RC 60 would have been plenty hard and a lot less prone to chipping.


Mike

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DRSS, Womper's Club, NRA Life Member/Charter Member NRA Golden Eagles ...
Knifemaker, http://www.mstarling.com
 
Posts: 6199 | Location: Charleston, WV | Registered: 31 August 2002Reply With Quote
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quote:
Originally posted by mstarling:
If you want to try that, I'd suggest using a round medium india stone about 1/2" in diameter along with a 1/2" square india stone. You can probably make the existing chip almost disappear.
The smith needs to know he went too hard.

The San Mai construction is designed to provide a hard material embedded in a body of more flexible material. Doesn't mean that one should get the hard material too hard! RC 60 would have been plenty hard and a lot less prone to chipping.
Okay, I'm in business. Thank you.

Regarding the high hardness range, for Cowry X it is within normally delivered parameters. Blade steel's reason for existence is its unusual hardness and abrasion resistance. When laminated in a San Mai manner, it exhibits no more real-world brittleness than D-2 at HRC 59-61 or an original Morseth blade.

I'll be able to confirm this -- either way -- within a few months. I wish I knew its age and previous owner(s). It appears used but, except for the chip, not abused.

Thanks again.


It's so simple to be wise. Just think of something stupid to say and then don't say it. Sam Levinson
 
Posts: 1443 | Location: Seeley Lake | Registered: 21 November 2007Reply With Quote
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Just forgedaboudit......you can probably screw it up more by fiddling with this inconsequential dent than leaving it alone. sofa


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Posts: 4263 | Location: Pinetop, Arizona | Registered: 02 January 2006Reply With Quote
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