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 Post subject: Re: Convex edge on an EP
PostPosted: Fri Jan 31, 2014 7:03 pm 
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Location: Cape Town - South Africa
LOL...so true....

:)



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 Post subject: Re: Convex edge on an EP
PostPosted: Sun Feb 16, 2014 12:52 am 

Joined: Sat Aug 24, 2013 2:42 am
Posts: 133
Well I finally did some work with the convexed Tanaka 210mm #2 blue gyuto.
Works well :)
It's probably not as convexed as what a belt would do but hey, the EP did it.
As I explained in my earlier posts the edge was 17° (true) and convexed down by approx. 1.2° .

In Lagrangians' post geometry-and-sharpening-systems-t5001.html ,figure 2 and 3 , he has worked out the drop in angle as you get farther from center.
A greater percentage drop in angle as the angle of the arm is lowered because the ratio of the hypotenuse to the opposite
is greater - sine function (I had no idea how to do it before I started this thread, amazing what an old man can learn).
He shows that the EP is not a planar function - intersection of two planes but the opposite side runs from the pivot to the
center line of the table.
Bottom line....sharpen as close to the center as possible for the most precise V edge. Real world-when going to the edge of the table you and the knife will never notice.

I still like a V edge but I thought I'd play around a bit. :)

Douglas


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 Post subject: Re: Convex edge on an EP
PostPosted: Sun Feb 16, 2014 5:10 am 

Joined: Wed May 02, 2012 11:14 am
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Location: Florida, USA, Earth
Langaranian's report is very thorough and covers a lot more than I can understand. But to keep it simple for me I picture a circle around the pivot rod (vertical one) at the same height as the end of the blade table. More accuratly would be a circle at the blade edge when sitting on the table. If the stone touches blade on either side of the blade table as long as the knife edge would follow the imaginary circle the angle would be the same. It's the distance from pivot rod to the blade edge that matters. If you extend the blade edge 1" beyond the end of the blade table the angle will go down approx. 1 degree. Lengthen any one side of a triangle and keep the angle the same at one end of the line the angle at the other end of the line will go down. And vice versa. So, as stated as a rule keep the portion of the edge you are sharpening in front of the blade table. But, the geometry I just talked about is about as deep as I remember from the 3 years in 10th grade geometry. :) I would have studied more if I knew it would help me understand knife edges. :D

Jack

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 Post subject: Re: Convex edge on an EP
PostPosted: Sun Feb 16, 2014 10:11 pm 

Joined: Sat Aug 24, 2013 2:42 am
Posts: 133
Not 1° for one inch , but a drop none the less.
In Lagrangians' post, figures 2 & 3, gives the change in angle. The pictures worked for me anyway. What he said about it..... :shock:
But yeah, you got it.

Douglas


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 Post subject: Re: Convex edge on an EP
PostPosted: Mon Feb 17, 2014 12:58 am 
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Lets remember that Lagrangians report examines the theoritical angle deviation. It is al literally so finite that

A) We cant measure it with any great accuracy
B) The EP has more play passively than the greatest deviation in the entire report.



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 Post subject: Re: Convex edge on an EP
PostPosted: Mon Feb 17, 2014 2:15 am 

Joined: Fri May 11, 2012 12:17 am
Posts: 122
Sadden,

There is a noticeable and measurable difference in degrees of angle in relationship of the pivot arm to the table of the E.P. To keep saying the E.P has more "play" is bullshit. When you are sharpening you are using consistent pressure so that play stays constant in relationship to the rod guide holder. Maybe you should try and build a few sharpeners and you would learn. The rod has to move sideways to keep a consistent angle perpendicular to the blade being sharpened. Or be built with arm being centered, precise angle arm length to table width.The only fixed angle sharpener I know of that addresses this the EdgePal .
http://www.youtube.com/watch?v=nynku3GQOoY#t=21


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 Post subject: Re: Convex edge on an EP
PostPosted: Mon Feb 17, 2014 3:19 am 

Joined: Wed Feb 20, 2013 2:22 am
Posts: 545
If I were smart I wouldn't participate in this thread, given the tone it has taken. Oh, well...

When reefing down to remove metal, noneck is correct and free play is controlled by force. But when using light pressure, as one should during finishing strokes, free play will be considerable. I just measured it at .75 degrees on my kit.

I am waiting for a rod end mod to be offered for the Apex, or I will gen one up myself if I find the time.


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 Post subject: Re: Convex edge on an EP
PostPosted: Mon Feb 17, 2014 4:12 pm 

Joined: Wed May 02, 2012 11:14 am
Posts: 186
Location: Florida, USA, Earth
Tall Dark and Swarfy wrote:If I were smart I wouldn't participate in this thread, given the tone it has taken. Oh, well...

When reefing down to remove metal, noneck is correct and free play is controlled by force. But when using light pressure, as one should during finishing strokes, free play will be considerable. I just measured it at .75 degrees on my kit.

I am waiting for a rod end mod to be offered for the Apex, or I will gen one up myself if I find the time.


I called your boss and told him what you think of him. You are now fired!!! So you have time to make a mod for the Apex. You were right. You shouldn't participate in this thread. Just kidding. Not fired. :D

Jack


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 Post subject: Re: Convex edge on an EP
PostPosted: Mon Feb 17, 2014 5:50 pm 

Joined: Wed Feb 20, 2013 2:22 am
Posts: 545
Hah! My boss has been fielding phone calls for the past two weeks from people who want me fired. No kidding. But he's heard it all before. It's like water off a ducks back to him.

Seriously, drilling a hole centered in the EP and mounting a rod and end there would be a start. Maybe Gucci it up with a rack and pinion elevation adjustment? I know there are some machinists lurking out there.


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 Post subject: Re: Convex edge on an EP
PostPosted: Mon Feb 17, 2014 5:55 pm 
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Joined: Wed May 09, 2012 3:59 pm
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Location: Cape Town - South Africa
"Seriously, drilling a hole centered in the EP and mounting a rod and end there would be a start. "

Like this.....

ep-pro-aligned-t3120.html


:mrgreen: :mrgreen: :mrgreen:



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