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 Post subject: Re: I am losing my needle point tips.
PostPosted: Thu Jun 12, 2014 6:40 pm 
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Joined: Mon May 19, 2014 1:52 am
Posts: 355
Location: Philly
If I have to fix a big tip chip I use a modified sharpie trick to help keep the geometry in tack. Just use the sharpie to color in the metal that has to be removed. Basically drawing a new tip then removing that metal.

If the chip is big going low grit will help speed. And if the chip is huge then it's time for sandpaper or files or preferably a belt sander.



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 Post subject: Re: I am losing my needle point tips.
PostPosted: Thu Jun 12, 2014 9:43 pm 
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Mikey's Deli wrote:SWEETNESS!
I love this. Knife sharpening is the bomb. I have never gotten into anything with this kind of passion, :geek: ever. (notice I didn't say obsession...?) :mrgreen:

Don't worry, the obession will come. ;)



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 Post subject: Re: I am losing my needle point tips.
PostPosted: Thu Jun 12, 2014 10:50 pm 

Joined: Sun Aug 11, 2013 11:00 pm
Posts: 37
It's a little too late now since you've fixed the blade but....

Looking at the pictures I think your angle at the last part of the blade, at the tip, is too low. Notice that the bevel gets wider as it approaches the tip? That's because you're not lifting the handle of the blade as you go through the curve. The cure is easy: Just follow the natural shape of the bevel by lifting slightly as you go through the curved portion.

As several others said, using sharpie on the edge will show you this visually. Check your progress until you are able to smoothly remove all of the sharpie, right down to the edge, along the entire length of the bevel. When I started concentrating on tips, I found that I wasn't raising the handle up enough at the *very* end. My blade ended up with sharpie left over in the last 1/8 to 1/16" . I kept modifying my stroke until I got all the sharpie to go away. From there, I used a loupe to inspect the tip. What I found was I could see roundness at the end. As I kept doing strokes, making sure to get the tip, and then *stopping* with the tip touching the stone... I found that I was wearing away the rounded part and leaving behind a more straight transition to the spine. Remember, I'm talking about the last 1/16" of the blade. A VERY small part. A 10X loupe makes it look much bigger and if you allow it to, it will let you get some REALLY sharp tips!

I've used the "grind down the spine" method in the past, and it has it's merits. But I disagree that it should be the "go to" method for tip repairs. I like starting from the edge side instead, as I feel this changes the shape of the blade less. Plus this is how Murray Carter teaches tip repairs, even on pretty big missing tips. He's got to know more than me about this subject.

As I continue learning about this, I think there is a balance to be had with both spine grinding *and* edge grinding to keep the geometry of the blade the same. But that's kind of a more advanced topic.

I would advise you to start with the edge on your next tip repair and see where it takes you. If you need specifics on that, I can write up a little something more about it.

Good luck,

Brian.


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 Post subject: Re: I am losing my needle point tips.
PostPosted: Thu Jun 12, 2014 11:21 pm 
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I have to agree Brian. I would only grind on the spine for a broken tip and even then I'd mix it with bringing up the edge too. I wouldn't grind the spine for a rounded tip, but there are many routes from point A to point B, puns intended. :D

Mike you just keep at it and you'll find what works best for you!



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 Post subject: Re: I am losing my needle point tips.
PostPosted: Fri Jun 13, 2014 1:15 am 
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Wow. Thanks guys. What a community we have here.
Thanks again.


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 Post subject: Re: I am losing my needle point tips.
PostPosted: Sun Jun 15, 2014 4:04 am 
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So yes going at it from the spine is THE way to go to get that point back and you've already gotten great advice on this point :)

So now let's talk about keeping a constant angle all the way to the tip. The concept of lifting the knife is a common but flawed explanation of how to do it. Look over this video for a pretty clear explanation of how to be completely consistent from heel to tip. It's a very simple concept but so confused by this 'lifting the knife' to do tips. Once you 'get' this concept, you will KNOW how to position the knife all the way to the tip in a very consistent manner.

While I use a belt grinder in the video, it is EXACTLY the same motion on a stone.



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Ken



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 Post subject: Re: I am losing my needle point tips.
PostPosted: Sun Jun 15, 2014 4:11 am 
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FWIW I bring the spine down on 95% of the knives I see to sharpen. Of course this sharpening for the general public and not the quality of knife we are talking about here. But still its part of sharpening.



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 Post subject: Re: I am losing my needle point tips.
PostPosted: Sun Jun 15, 2014 4:17 am 
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Sweet, guys. Thanks!
This is great stuff. Love the vid Ken.


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 Post subject: Re: I am losing my needle point tips.
PostPosted: Sun Jun 15, 2014 6:24 am 
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Glad to help. This video and the asymmetry video I seem to bring out every so often. It is a simple topic but there is so much hoha about lifting and twisting a knife for the tip that it amazes me when someone wades through all the BS and actually 'gets' that it is as simple a concept as being consistent from heel to tip. You will really hear a lot of this crap regarding yanagis and how these mystical Japanese senseis have instilled these highly complex secrets on a select few Americans who 'know' just the right way to twist a knife. Hysterical, really.

Since that plastic knife was my first knife, it isn't for sale LOL.

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 Post subject: Re: I am losing my needle point tips.
PostPosted: Tue Jun 17, 2014 12:33 pm 

Joined: Sun Aug 11, 2013 11:00 pm
Posts: 37
Ken,

Your video showing how to follow the curve is brilliant. Excellent work. I've watched it 3 or 4 times in the last few months.

There's something subtle though that I don't think you're considering. In a blade made from thicker stock, as the blade curves toward the spine, the edge bevel must do one of two things:

1. Bevel stays at the same angle, but the width of the bevel increases as it nears the spine. This necessarily will happen, as the edge is being cut from thicker and thicker stock as it approaches the spine. The bevel near the tip will be wide and won't look visually appealing.
2. Bevel width is held constant, so the bevel angle gets larger (higher edge angle), as it approaches the tip. This keeps the visual width of the bevel even and appealing, but doesn't hold a "perfect" constant angle.

I think this is all true both due to logic and having created a wider tip on one of my blades while using a sharpening "wedge", which props up a sharpening stone at the desired sharpening angle. One then holds the blade parallel to the table the wedge is resting on and grinds the bevel. Using this tool/technique, the bevel width at the tip of my Spyderco Tenacious became larger and not all that visually appealing. It's possible I made a mistake in my technique, but I don't think so. I think #1 above applies.

If my logic and observations are true, then the motion of the blade on stone or belt must change slightly as the curve goes closer to the spine, *IF* one wants to maintain a visually even bevel. I do this on bench stones and the WorkSharp Ken Onion by changing the angle a tiny bit in the last 2/3 of the curve inward.

I actually do this mostly by feel, as one can feel when the bevel is resting flat on the stone or belt. Thus I try to maintain approximately the same bevel geometry from the factory, assuming that the geometry was good to start with. Otherwise, I have to recreate my own bevel, stopping to inspect and make sure I'm getting it right as I go along.

Thanks for reading.

Brian.


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