Knife tip grinding - To Pivot or Not To Pivot

[Kavik]

(accidentally hit submit early....pls hold)

[Herman Trivilino]

Any chance you could delete the annoying photobucket images and replace them using the forum attachment program?

I'm having trouble finding the originals, but haven't given up yet. I'm also trying to download them from photobucket but haven't yet figured out a way to do that.

[Kavik]

You're absolutely right Ken, and if it weren't for this topic I'd still be trying to learn the "right" way with the stock components.....that said, here's what I've come up with that seems to work pretty damn well so far:

First, the drawbacks of a cut down collar: you need to focus a little more on a) keeping the knife flat to the stone when working on the straight edge of the blade and b) keeping the jig on the USB without slipping off
Second, the perk: the pivot point becomes practically stationary, as opposed to moving drastically, as shown in the second row of the pic cbwx posted above

So here's what I did...I cut the wide end off one of my jigs, created a modified template (based on Ken's 139mm length, with cues from Jan's tip projection template, with a couple of twists) then tested the setup with 7 different blades and multiple distances on the USB in both the horizontal and vertical position.

Attachment 1 shows the blades tested, ranging from 3.75" to just over 8" in varying profiles
(the jig has the stock collar on it, obviously...the cut down collar is sitting above it)
Attachment 2 shows one of the knives set up in the jig to set the blade protrusion and to eyeball the horizontal protrusion of the tip

The idea here was that if the tip is going to have the same bevel angle as the flat of the blade, then the tip has to stay on the LOC, therefore the distance has to be the same 139mm from the pivot point to the tip.  With the stock jig collar this is impossible to do as that thing is 55mm wide and moves the pivot point by a very large amount.

So to explain my template look at attachment 3: I drew the same box to line up the clamp and set the blade projection like we see in Ken's jig template. I then drew a 45 degree angled line at the same 139mm length. Important to note that the 45 degree angle lines up with the SIDE of the center post of the jig, not in the center of it.  I then set the blade projection and by eye I follow the curve of the blade, extending an imaginary line to the end of the 45 degree line on the paper (as illustrated by the green curve)
Attachment 4 shows the most extremely curved tip set up the same way

Once this was set I was able to keep on the LOC from the heel to the tip.  I'll explain how shortly, but first I want to go over the second part of the test.
Leaving the knife in the jig I swapped back to a stock collar and tested how the blade rode on the wheel.  The chart below shows the distance from the LOC at the highest point I was able to get the tip to with the stock collar  (I think I was set up at a 20 degree angle at that point, and this is on a 230mm wheel)
(same order as the picture)

Knife	distance below LOC
Cold Steel SRK	-7mm
Gerber (BG)	-9mm
Old Hickory Butcher's knife	-12mm
Old Hickory Slicer	-10mm
Maxim Chef's	-6mm
EdgeMark Hunter	-7mm
Gil Hibben's Throwing knife	-7mm

I'm going to have to finish this in a second post, as I'm out of room for attachments

[Kavik]

Part 2:

Attachment 1 shows the cleaned up version of the template (if anyone wants to print it out and test this theory, just make sure to scale it so that the black rectangle is 45x139mm)
Black box is placement of the jig
Red line marks the blade protrusion to 139mm
Blue lines indicate the width of the jig's center post
Orange line is the target for eyeballing the tip projection
Light grey and purple lines are reference points only at this time, for checking the arc of travel

Attachments 2 and 3 show an overlay of the 2 knives in the jigs and how they line up to the 45 degree 139mm line and continue their travel along the purple arc.
Note that these arcs intersect at the tip of the orange line and are NOT intended to overlay each other.  The arcs in attachment 3 are close by coincidence only, due to the slope of the tip on that particular knife.

Once this was all set up as described above, here's the method for the motion to use:

• start just as always, I will be describing starting with the tip of the knife pointing to the LEFT
• while grinding the straight length of the knife slide the jig to the right, with no pivoting or lifting until you reach the curve
• once the knife begins curving down to the tip pivot the knife (keep level, pull the handle towards you) until you reach the apex of the curve
  at the same time begin sliding the base of the jig slowly back to the left, to keep the pivot point on the USB and the LOC along the width of the stone in line with each other
• This step will vary based on the severity of the curve to the tip
  
  
  
  • If continuing to pivot does not cause the tip to rise above the LOC then you are all set
  • If continuing to pivot will cause the tip to rise above the LOC then you would now lift the handle in addition to pivoting

Sounds more complicated then it is. After a couple of tries it just felt "right", if that makes any sense? It's a very fluid and natural motion. If you focus on the shape of the blade in your mind, it's like your hands are tracing the contours.
I plan to test it soon with actually grinding, but I'm afraid I just ran out of time today.  I think the theory is sound though, distance stays the same, LOC stays the same, pivoting keeps the wheel perpendicular to the face of the blade even as you round the curves.  If there's anything glaringly obvious that I've overlooked please let me know!

[cbwx34]

Kavik... thanks for doing all this.  Here's my inital thoughts...

It's funny... I was going to suggest cutting the collar off a jig... but didn't want to do it myself, (and don't like suggesting something I won't do).  Glad you did it.  I think just eliminating the sides of the collar (so that the jig could still "ride" on the USB, yet still pivot without significantly altering the pivot point), might get rid of some of the 'drawbacks'.  (BTW: from your earlier post about the lock screw getting in the way... the newer knife jig eliminated the lock screw completely).

Your comment that "after a couple of tries it just felt 'right'"... is what I referred to earlier... that pivoting a knife with the current jig, doesn't feel like a natural motion (and hinders the ability to maintain the LOC).

I think the template is a good reference... but want to point out that it's not really a part of the setup.  It does combine it with Ken's Kenjig setup and purpose though.  In reality, the only real 'guide' needed is to properly set the knife in the jig, so that the belly/tip area is approximately the same distance as the flat portion from the pivot points.  But the template is a good way to do that, and gives a "standard" to work from. (Hope that makes sense).

All in all, I think your testing was well thought out... and seems to validate what I'm thinking.  Hopefully your actual testing will further validate it.  Interested to hear what others have to say.  Thanks again!

[Kavik]

I was planning to cut one down anyway, for the idea I had earlier about trying different profiled curved "caps" for it.... Which I think could be a moot point now, we'll see

I know I skipped a lot of the thought process and the steps that got me to that final plan, but:

In reality, the only real 'guide' needed is to properly set the knife in the jig, so that the belly/tip area is approximately the same distance as the flat portion from the pivot points.

Yes, this is exactly what that orange 45 degree line does. I don't know about you, but I can't "eyeball" that long of a distance at 2 angles

Tormek suggests setting this by matching the length of tip protrusion to the height from the shoulder of the jig (I'm not explaining that well, but a picture can be found in the manual)
What I found was that this worked perfectly fine on a couple of my knives, but it seems it was the profile of the tip that determined if setting up like that would result in the tip finishing at, above, or below the LOC, even with the cut down jig collar.  (to really prove this i would have to set up each knife with the stock collar again, using the recommended method for tip protrusion and measure them out again and add those measurements to my previous table, but I'm not home at the moment to do that)
That's the part that lead me to the conclusion that a 139mm line at a 45° angle would get me there every time (and looking back now, perhaps the purple arc is all that is needed there. Again, similar to Jan's tip setting jig, just altered to use the small pivot point instead of the wide collar profile)

If you look back to the attachments in my first post, 3.jpg is the Cold Steel SRK. This one was, in fact, close to the Tormek suggested settings: equidistant horizontally and vertically from the shoulder of the square part of the jig.
But if you look at the butcher style knife in 4.jpg, you'll see that a tip with that extreme of a curve ended up needing the jig set much further away from the tip in order for it to reach the LOC.

Again, just thoughts for now, I know.  The proof will be in the pudding, so to speak, when i do some actual sharpening like this. Gonna try to find some time in the next couple of days

[cbwx34]

In reality, the only real 'guide' needed is to properly set the knife in the jig, so that the belly/tip area is approximately the same distance as the flat portion from the pivot points.

Yes, this is exactly what that orange 45 degree line does. I don't know about you, but I can't "eyeball" that long of a distance at 2 angles

I agree... and perhaps didn't say it right.  You can accomplish the same thing just by measuring the distance, (like in the attached picture).  The 139mm is more what I was thinking isn't really a part of the process... it's just a convenient measurement... especially, since, as Ken pointed out... a lot of knives fall close to that.  But you can accomplish the same thing at any length.  (Probably still clear as mud haha).

I think the pudding will come out fine.

[Kavik]

Oh, yeah. I gotcha.  Yup, the 139 was just an easy enough starting point for me,  but you're right, it's the equal distance that matters, not the actual length.

But it is sure nice having it there on paper to just lay the knife/jig against, instead of measuring each one with a ruler like that 

[Kavik]

Okay, so.....the experiment kind of worked. Not quite as spectacularly or as groundbreaking as i might have hoped for, but there did seem to be benefits.

I need to continue practicing more, but the cut down collar and using the arc to align the tip with the 45° line as measured from the left side of the jig shaft DID  result in me being able to keep the entire length of the blade at (or very near) the LOC. Whereas setting the tip protrusion per Tormek's instructions and/or using the stock jig collar often left me unable to even come close.

Like I said, I need more practice to get it down consistently, but I managed to almost get an even bevel angle all along the length of that 7" butcher knife with the most extreme belly to tip transition (third one down in my first pic of all the knives). This was the one that fell the furthest below the LOC using the stock jig. So I remain optimistic, if still inexperienced lol
Bevel width changed a bit at the transition to the tip, but not as drastically as I've had with other methods, only what one would expect for the change in blade thickness as the tip approaches the spine.

I'll need to visit a thrift shop and find some more junk knives to keep practicing on,
And i think maybe round off the shoulder on my cut down collar just a bit

[cbwx34]

Okay, so.....the experiment kind of worked. Not quite as spectacularly or as groundbreaking as i might have hoped for, but there did seem to be benefits.

I need to continue practicing more, but the cut down collar and using the arc to align the tip with the 45° line as measured from the left side of the jig shaft DID  result in me being able to keep the entire length of the blade at (or very near) the LOC. Whereas setting the tip protrusion per Tormek's instructions and/or using the stock jig collar often left me unable to even come close.

Like I said, I need more practice to get it down consistently, but I managed to almost get an even bevel angle all along the length of that 7" butcher knife with the most extreme belly to tip transition (third one down in my first pic of all the knives). This was the one that fell the furthest below the LOC using the stock jig. So I remain optimistic, if still inexperienced lol
Bevel width changed a bit at the transition to the tip, but not as drastically as I've had with other methods, only what one would expect for the change in blade thickness as the tip approaches the spine.

I'll need to visit a thrift shop and find some more junk knives to keep practicing on,
And i think maybe round off the shoulder on my cut down collar just a bit

Thanks again for doing this.  (You and I may be the only ones interested...).

I learned, dealing with another guided sharpener, that most knives can be set based on the belly/tip area... and that the setting actually falls within a pretty similar distance between knives.  (Not surprising, since basically, all you want is the belly/tip area approximately the same distance as the "flat" portion from the pivot point(s)).  But, as you indicated... hard to find a "perfect" fit.  Still, this appears to me to be a better more consistent approach, than the difference the current collar creates in how it keeps the knife near the LOC.

Even the experiment where I didn't use the stop collar at all, and kept the knife at a laser line... I could tell as I tried a few knives that some knives needed a slightly different approach toward the tip... a slight lift, etc.... so doubt if any jig would be "perfect".  But hopefully, we're getting closer.

The experiment continues.... 

[Kavik]

My pleasure And that's okay, I think it's obvious I don't mind rambling, even if it only helps one person lol

I dunno, I still think a platform and a bit of practice might be more ideal than any pivoting jig... I just haven't gotten around to trying that method yet (I kinda get stuck on one thing once i get an idea in my head, and have to play it out till the end before I try the next approach)
But, yeah, if you're going to pivot a jig, i don't think you can ever really hope for consistency unless the pivot point itself is consistent. (In an ideal world, with unlimited tools and resources at my disposal,  the solution i would create for a perfect pivot point is way more involved than anything I'm actually going to go into for this  )

I do need to set up one of those laser lines though. I think the inconsistencies I had in my bevel angles were due to losing track of the LOC while just trying to eyeball it to a point on the body of the grinder

[cbwx34]

My pleasure And that's okay, I think it's obvious I don't mind rambling, even if it only helps one person lol

I dunno, I still think a platform and a bit of practice might be more ideal than any pivoting jig... I just haven't gotten around to trying that method yet (I kinda get stuck on one thing once i get an idea in my head, and have to play it out till the end before I try the next approach)
But, yeah, if you're going to pivot a jig, i don't think you can ever really hope for consistency unless the pivot point itself is consistent. (In an ideal world, with unlimited tools and resources at my disposal,  the solution i would create for a perfect pivot point is way more involved than anything I'm actually going to go into for this  )

I do need to set up one of those laser lines though. I think the inconsistencies I had in my bevel angles were due to losing track of the LOC while just trying to eyeball it to a point on the body of the grinder

I agree... Herman's platform setup is probably the ideal route... sharpening on a platform is probably the closest thing to freehand sharpening, with the advantage of a guide.  Eventually, I might give it a spin.

I'm always torn between the "science" of sharpening... guides, precise angles, etc. vs. the "freedom" of freehand.  Adding the laser guide is a definite plus... at least there's some degree of accuracy (pun intended), although certainly not the same as an actual guide.  I'll still pursue an ideal jig setup... but most of my actual sharpening... I'll concentrate on improving my freehand results.

[Kavik]

You know what's the worst part of this? All the thought I'm giving this issue, and i really don't intend to use this for much knife sharpening anyway lol

Bought it for the tool sharpening, i enjoy my bench stones for my knives too much to give that up, even if I did come up with a perfect jig.
Something to be said about the routine there, setting up and soaking the stones, then just putting on some music and relaxing while working up through the progression.
To me the tormek is functional, efficient, an apt tool when you want to get through the job.
Whereas freehand sharpening on the bench stones is something I'll do for the sake of doing it sometimes. It's as much about enjoying the process as it is about the end result

(not the same for chisels, planes, or turning tools. Those are always a chore in my mind, so the quicker and more accurate the better)

[cbwx34]

You know what's the worst part of this? All the thought I'm giving this issue, and i really don't intend to use this for much knife sharpening anyway lol

Bought it for the tool sharpening, i enjoy my bench stones for my knives too much to give that up, even if I did come up with a perfect jig.
Something to be said about the routine there, setting up and soaking the stones, then just putting on some music and relaxing while working up through the progression.
To me the tormek is functional, efficient, an apt tool when you want to get through the job.
Whereas freehand sharpening on the bench stones is something I'll do for the sake of doing it sometimes. It's as much about enjoying the process as it is about the end result

(not the same for chisels, planes, or turning tools. Those are always a chore in my mind, so the quicker and more accurate the better)

I do enjoy some "stone" time... but have found that using the Tormek can be just as enjoyable.  One of the reasons I returned to using it more. 

[Kavik]

Well, finally got some time to finish this small collar idea tonight...... And gotta say it's much nicer than just the straight cut off version.
Turned a little nub on the end of some acrylic blank I had laying around here...but if i were too do it all over again, this could all be done with the stock collar piece chucked up in the lathe...I just felt I cut the first one a bit short anyway
Still no laser line, but i think i did better keeping to the LOC

Operation feels very very smooth. Setup was the same as mentioned previously with my template. Pivot point seems to remain on the side of the shaft (on the side towards the tip), not in the center of the jig shaft

As I hope you can see in the attached pic, the bevel width looks pretty good.
Bevel angle isn't perfect, but it's close all along the length (sorry, i don't have any fancy accurate measuring tools for that).
With the exception of a couple extremes (user error), the bevel width is 1 to 1.4mm. Again, without any serious measuring tools, i think this seems about right for the difference in blade thickness at the heel, belly, and tip


At this point I think i can do pretty well with this collar and setting up something to mark the LOC, with just a bit of practice.
Definitely finding it MUCH easier to keep smooth/even transitions and bevels than the wide stock collar was, so for this part I think I'm now satisfied 

(apologies for the crap pictures, don't have any good options for resizing here in my phone too meet the attachment size limits while still keeping good detail)

P.S.
Also don't be thrown off by the crazy wide marker on the blade. I wanted to be sure to cover all the old grind experiments, so I just went with a really fat marker right up over the bevels and onto the face