Kershaw Cryo2 Uneven edge

[Brandon]

Good morning, I have had my Gen3 Pro since August and I love it.  I am having a difficult time with sharpening my Cryo2.  I place my blade in the clamp (top section), and my measuring guide has the tip of the blade at location “DE”.  I am sharpening at 17 degrees per side.  For some reason, I am getting this uneven sharpening on the circled area.  Any ideas?

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[Marc H]

If I were to take a guess, it appears the thumb stud may be hindering your sharpening stone from sharpening down as low as it can sharpen forward, (i.e., towards the tip), of the thumb stud.  Is it possible to remove the thumb stud to allow clear access to the knife bevel edge by the sharpening stones?

Marc
(MarcH's Rack-Its)

[Readheads]

What did the profile look like before ?

I do not think the screw is interfering as there are no marks on it. Did you get a perfect burr along the full edge ?

[Brandon]

Yeah the thumb stud is not being touched by the stones.  Before sharpening it was perfectly straight.  I do have the thumb stud right up against the one side of the clamp as far as “location of clamping”. Yes the burr is forming on both sides.

• This reply was modified 4 years, 11 months ago by Brandon.

[Marc H]

Another suggestion, is there any paint abraded from the vise or jaws indicating the stone was contacting them befre it allowed to make full, flat contact on that heel portion of the bevel.

Also, I was hoping you had the thumb stud protected with tape, which was why it didn’t show damage.

I do try to clamp knives in the center of their length so there is as much edge forward of the vise as ther is behind the vise.

Marc
(MarcH's Rack-Its)

[Brandon]

No missing paint from the vise (aside from previous accidents) haha.  I will try moving the blade in the vise and resharpening.

[Marc H]

Brandon wrote:

No missing paint from the vise (aside from previous accidents) haha.

Suggestion: Blacking over the previous stone scuff accidents with a sharpie marker helps you recognize new boo boos.

Marc
(MarcH's Rack-Its)

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Brewbear

[Lay]

Is the blade/edge near the sharpening choil thicker? It might change the sharpening stone angle and cause recurve and uneven edge when sharpening.

• This reply was modified 4 years, 11 months ago by Lay.

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Brewbear, Marc H

[Lay]

This youtuber called TheApostleP explains it better.

Right around 23 minutes and 45 seconds in this video: https://youtu.be/T9HzJM7IKPg?t=23m45s

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Organic, Marc H

[Brewbear]

Thank you @Lay, that was very good, I did get that kind of uneven sharpening on one of my knock about knives and now I know why. Much appreciated.

1 user thanked author for this post.

Lay

[tcmeyer]

The “dip” just forward of the ricasso is usually a result of using the same diagonal strokes throughout the length of the edge.   If you consider that the very last point on the edge (at the bolster, where the stone comes to a complete stop) sees almost zero inches of abrasive passing over it when compared to the rest of the edge, you’ll recognize that there will be much less material removed at that point, compared to the rest of the edge.

If your stroke moves the 3/4″-wide stone upward (or downward for that matter) at a 45 degree angle, each point along the edge will see about 1.06″ of abrasive  (3/4″ * sine of 45) passing over it with each stroke.  This is not true for that last 3/4″ of the edge as the stone approaches and hits the bolsters, bringing it instantly to a stop.  That last 3/4″ will see a proportion of that abrasive length, decreasing linearly down to zero.  At 3/8″ from the end, the amount of abrasive will be one-half of the 1.06″ or 0.503″.  At 1/4″, it will be one third, or 0.354″.   Of course, the numbers change if the angle changes, but at the very end, the number is again, and always zero.

Perhaps the easiest correction would be to use very vertical strokes for the part of the edge near the bolster.  Starting at the bolster, use nearly vertical strokes and as you move away from the bolsters, decreasing the vertical angle as you move along the edge until you are down to your normal diagonal angle about mid-way on the edge, so that you can finish the belly and the tip with your normal strokes.

Here’s a photo showing what a stroke pattern might look like:

If the error seen at the heel is too visible, you can make further corrections by applying slightly more pressure on the side of stone nearest the heel.

You can correct for the differences in bevel width by abbreviating the  strokes at various points along the edge.  The varying of the strokes’ starting and ending points will serve to blend the scratch patterns.  In any case, you can “hide” the varying scratch patterns by carrying the session to a near-mirror polish.

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Brewbear, Dwight Glass, Organic, Brandon

[Brandon]

Thank you.  This was corrected by moving the blade a little back in the clamp as well as the motions mentioned by tcmeyer!

1 user thanked author for this post.

tcmeyer

[Jeff]

It appears you have found a solution already.  I will add, however, that I have a Cryo that I have sharpened many times on a WE system.  My edge looks somewhat like yours but not near as pronounced.  I believe it is because of the shape of the blade.  How the hollow grind sweeps up towards the ricasso.  It is quite a bit thicker in that area.  I find I have to spend extra time with the stones in that area to thin it out and keep the phenomenon you are seeing to a minimum.

[Author]

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