Problem: Uneven Grinds (MINE not Spyderco's)

[Bolster]

This may be majoring on minors, but it's causing my OCD to act up, so I thought I'd ask for help. I'm sometimes getting uneven grinds of my own making when sharpening on my Hapstone R2. What am I doing wrong. First photo is of a Caly Jr, where one side sharpens with a nice even line, but the obverse sharpens so the grind is wider at the tip. (The Hapstone has a flip device, where you easily flip the clamped knife back and forth between sides.)

[Bolster]

Here's a Manix, where the grind line widens toward the tip on both sides - unhappy with my performance on this one:

[Bolster]

And here's how I use the Hapstone R2. I try to center the clamps on the arm as seen on the left. Then I try to orient the knife so the (curved) edge is more-or-less perpendicular to the sharpening rod (that carries the stones not shown in the photo). The reason I'm emphasizing this, is that with this mostly-perpendicular orientation of the knife to the jig, I am trying NOT to have the grind line widen in one area or another. Obviously if the knife were clamped so the spine (rather than the edge) were perpendicular we'd expect to see widening in areas where the stone is reaching the farthest (right?).

[Bolster]

If not clear, here's what I mean by perpendicular...trying to get a nice 90 degree angle on the imaginary T, so that most of the blade is as perpendicular as possible, or "perpendicular on the average," to the jig. I thought this would limit the widening of the grind toward the tip, but perhaps I'm under-doing it, not adjusting enough? Or am I making some other error that is causing me to get wider-at-the-tip grinds?

They're plenty sharp, the edges work great, but as I said...it's making my OCD act up.

[JSumm]

So it is not just my cheap WS Precision Adjust that does this. One of the reasons I stopped and went back to hand reprolfiling.

[endura3]

I used to run into this issue sharpening on a KME, and it was one of the reasons I went back to freehand sharpening on bench stones as well. I think you're thinking about the issue correctly - the problem I'd run into is that tiny deviations away from "perpendicular" as you describe it would lead to the same effect with a varying bevel from tang to tip. I'd be curious to hear any thoughts from those more experienced with guided systems as to how this can be avoided.

Although in your last picture with the red dashed "T", it looks like the tip is a little further from the midline of the T than the base of the edge at the plunge line. That would likely account for the variance you're seeing, right?

[Bolster]

Although in your last picture with the red dashed "T", it looks like the tip is a little further from the midline of the T than the base of the edge at the plunge line. That would likely account for the variance you're seeing, right?

A definite possiblity. I've been perpendicularizing casually by eye, thinking more-or-less was good enough (as in the above photo), and not thinking that loads of precision in the setup was needed. Maybe very small differences/irregularities of distance from the pivot point of the sharpener make a big difference? I may need to use a measuring tape (or perhaps a T-shaped measuring stick?) and use it to get the heel and the tip of the knife exactly the same distance from the pivot.

That is not a step I've taken to date. Maybe the fix is simply more precision in setup.

[dsvirsky]

Off the top of my head, but have you considered the possibility that the bevel changes in width because the thickness of the blade changes with the distal taper? When sharpening freehand, one can compensate but a fixed system is just that -- fixed.

[dull&blunt]

Off the top of my head, but have you considered the possibility that the bevel changes in width because the thickness of the blade changes with the distal taper? When sharpening freehand, one can compensate but a fixed system is just that -- fixed.

This was my thought too. The blade is thicker towards the spine. On a fixed system it's going to create a wider bevel at a lower angle.

[Zipper]

Off the top of my head, but have you considered the possibility that the bevel changes in width because the thickness of the blade changes with the distal taper? When sharpening freehand, one can compensate but a fixed system is just that -- fixed.

This was my thought too. The blade is thicker towards the spine. On a fixed system it's going to create a wider bevel at a lower angle.

I agree when a distal taper is in play, being close to 90 degrees to the ‘T’, will give an uneven grind. If the OP wants to preserver with the guided system, experiment with being off perpendicular. Almost the opposite to what happens when distal taper isn’t much of a factor and being unevenly clamped in the blade causes an uneven grind.
The other variable that has caught me out with a guided system is when there is a slight warp in a blade (usually on older longer fixed blades).

[Bolster]

Is the suggestion above ^ that clamping as seen below would make for a more even grind line? With the tip closer and the heel further away from the pivot?

Is it possible that the spine of the blade, not the edge, should be perpendicular?

(Or should a line midway between edge and spine be made perpendicular?)

[Zipper]

Hello Bolster. How you have it now, I would hit the edge with a sharpie marker and try it. Just use a fine stone and you will see where it is hitting the blade. Re-mark the edge and adjust as you go.
I think it would be more coincidence than the rule if it so happens the spine is perpendicular. I think all knives will be slightly different. It would be great if that is the case for this knife, then it would be easier to remember.
I take a photo of the position of each knife I put in my KME system and try to replicate that at subsequent sharpening. The sharpie trick helps me confirm I am in the right spot.

[AHarbuck]

I imagine if you play around with different non-perpendicular variations in positioning you can split the difference and even things out. Would still likely be a wider bevel at the extremes of the stone’s reach from the center of the clamp, but you could minimize it as much as possible, and maybe it won’t be as noticeable to the eye.

I’ve had success with KME by using a straightedge and pencil to mark the blade from where the edge hits the heel to the tip, then marking the midpoint of that line as a reference when clamping. I still do get some slight variation, but I haven’t seen it as wide as yours. Haven’t tried it on the models you pictured, though.

[Bemo]

This has always perplexed me and seems a bit unavoidable with fixed/guided systems. Trying to match the arc of the path the stone/rods want to take and the arc of the blade. For me imagining the arc is the key and not using the spine as much for the indexing point. Also keep in mind that all the blade dimensions can have variances in 3 dimensions. I have the Hapstone as well and have noticed bevels being uneven periodically as well but my OCD takes a lot more to be triggered I guess. Plus I've botched bevels worse hand sharpening.

[Bolster]

I take a photo of the position of each knife I put in my KME system and try to replicate that at subsequent sharpening.

Thanks for reminding me...I went back and searched, and yes, I did take a photo of this M4 Manix during its initial sharpening. Placement doesn't look perfect, but not horrible, either. I'll definitely be more careful about setups in the future, and will try the "mark a straight line from heel to tip with a sharpie and mark the midpoint" trick mentioned above.

[RustyIron]

There's something different side-to-side.

Could it be the clamping? The blades are tapered, so the clamps might not be holding the blade in perfect alignment with the plane of the holder.

Is it possible that the flippy-flop mechanism is not a perfect 180 degrees?

[Wandering_About]

My 15V Manix was a few thousandths of an inch thicker behind the edge at the tip compared to at the ricasso. I'm not sure if this was due to factory sharpening or the primary grind, but I sharpened it freehand and it still is slightly thicker BTE at the tip than at the ricasso. It really doesn't bother me as it's not too severe, but then again my edges are a little on the crazy side and will never win any kind of edge beauty contest.