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angles on clamp style devices
- Thread starter olddogrib
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Yes, the floss helps
you guys are right, the angle doesn't change, the floss lines up, same model as in previous picture (where I measured wrong angle) just different perspective, angle must be the same
originally I was only going to comment regarding the angle changing/lowering when you reach curved area of blade(like tip) ... got confused somewhere and started playing with sketchup/inkscape
and it didn't help my confusionin my original image I measured the wrong angle, not at 90 degree to the edge , thats why it was different , just had to look at it sideways to see the angle is the same because the floss lines up
originally I was only going to comment regarding the angle changing/lowering when you reach curved area of blade(like tip) ... got confused somewhere and started playing with sketchup/inkscape
in my original image I measured the wrong angle, not at 90 degree to the edge , thats why it was different , just had to look at it sideways to see the angle is the same because the floss lines up
It is fun having that Eureka! moment isn't it?
Thanks!
Frans
- Joined
- Sep 23, 2014
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yupIt is fun having that Eureka! moment isn't it?
Thanks!
Frans
the friendly atmosphere helped, thanks
I have all of the above systems and than some
The principle is the same for all the clamping systems. As long as we are talking about a straight edge that is clamped in such a way that it is parallel with the back of the clamp than the angle will stay the same along the entire length as illustrated in the previous three photos.
The problem seems to be that a lot of people do not understand the principle and for example only look at the angle of the sharpening stone lengthwise (which changes but that is not the angle at which it sharpens). They do not notice that the stone also has another angle which is sideways and which does not change. It is this angle that sharpens the edge.
In the second photo, the lengthwise angle of the ruler is higher than the lengthwise angle in the 3rd photo where it is closer to the tip but as can be seen on the angle cude, the angle as measured across the ruler sideways (the way it sharpens the edge) stays the same
The knife should of course be clamped securely and not move under pressure of the sharpening stone.
I was more referring to the "tilt" of the knife when clamped rather than the angle going along the edge while sharpening. The clamp systems I've used (DMT, KME) both change the angle of the blade. The KME (well mine anyway) is very hard to keep the knife at zero degrees (relative to the stones) on both sides. Once clamped, the clamping pressure, and the imperfect fit/tolerances of the device, tilts the blade slightly in one direction, not holding it perfectly zeroed (flat). The DMT I've noticed, changes the stone to blade angle (quite a bit actually) as you increase or decrease clamping pressure via the clamp screw knob. This seems to be due to the flexy nature of the polymer bending while clamping.
I understood what you were referring to but apparently my English was not good enough to let you know, sorry for that.
Ideally, the clamp should exactly follow the taper of the knife and also have a stop that keeps the knife at the same depth in the clamp so it is perfectly centered and can not tilt.
Using things like tape or a piece of leather or something similar often helps but not always and that is one of the reasons why I have so many different systems so I can use the one that works best for a particular type of knife. It is of course total overkill and I can get very good and perfect working edges freehand with just a stone but for me sharpening is a hobby and I enjoy playing and experimenting with all those systems.
I agree with your observations.
I like the KME although it is absolutely not perfect. I use it with knives that work well with the clamp and I support it because I like that it is made by a small family owned company that cares a lot about customer service.
I very much dislike the clamp of the DMT but I often use the stone holder and stones with the Lansky clamps (old style clamps with the notch for small blades).
It works perfectly with those as they work at the same angle as the original Lansky stones.
Frans
yup
I must admit that there were moments that I thought...... damn.... how can they not see it, it is so obvious
I do however try to remember that although I am sure I am right, I might actually be wrong and /or that it might also be my inability to present the right arguments.
In any case I will always try to keep the conversation friendly and as long as someone takes the time to present arguments about why they think that they are right, I will always listen and try to understand them.
So thanks to everyone that participated in this thread and were willing to listen to my arguments or present their own. :thumbup:
Frans
Hi all,
I have read this thread with great interest, and I have come to the conclusion that to enter this discussion,
one would either have to be very skilled, very brave or just plain stupid. I am not sure in which category I
fit, but I am of the opinion that there are more things going on than "just" angles when it comes to
clamp style devices. Please take a look at this illustration:
The Contact area (i.e. the area where the hone is in contact with the blade) grows as soon as you leave
the straight 90 degree position. In consequence, the pressure per mm[SUP]2[/SUP] will be lower (which
will alter the grinding efficiency). Also, what effect will our change of grinding direction have on the final
result?
Have fun!
Claes
I have read this thread with great interest, and I have come to the conclusion that to enter this discussion,
one would either have to be very skilled, very brave or just plain stupid. I am not sure in which category I
fit, but I am of the opinion that there are more things going on than "just" angles when it comes to
clamp style devices. Please take a look at this illustration:
The Contact area (i.e. the area where the hone is in contact with the blade) grows as soon as you leave
the straight 90 degree position. In consequence, the pressure per mm[SUP]2[/SUP] will be lower (which
will alter the grinding efficiency). Also, what effect will our change of grinding direction have on the final
result?
Have fun!
Claes
Last edited:
I think that the amount of pressure applied when sharpening and whether that would have an effect on the final result would be an whole other discussion and is not exclusive to clamping devices
What I can add from my personal experience is that when I sharpen a knife, the amount of pressure I apply varies constantly also depending on the grid and type of stone.
Usually I do not apply a lot of pressure but let the stones do the work. I would not even be sure but I think that I use more pressure with natural stones than with diamond stones and the finer the grid, the less pressure. I would assume that the human factor in this case is of more importance than the area of the stone that is in contact with the edge.
The more you use a particular system, the more you get to know it and adapt your process. For example with the Wicked Edge you can often also hear if you are getting an even result or if some parts of the edge need more work. I think Clay Allison also talks about this in some of his videos and you can clearly hear the different sounds.
I think that in the end, I look at the edge and adapt the pressure and / or direction off the stone in order to achieve the result that I want.
Frans
What I can add from my personal experience is that when I sharpen a knife, the amount of pressure I apply varies constantly also depending on the grid and type of stone.
Usually I do not apply a lot of pressure but let the stones do the work. I would not even be sure but I think that I use more pressure with natural stones than with diamond stones and the finer the grid, the less pressure. I would assume that the human factor in this case is of more importance than the area of the stone that is in contact with the edge.
The more you use a particular system, the more you get to know it and adapt your process. For example with the Wicked Edge you can often also hear if you are getting an even result or if some parts of the edge need more work. I think Clay Allison also talks about this in some of his videos and you can clearly hear the different sounds.
I think that in the end, I look at the edge and adapt the pressure and / or direction off the stone in order to achieve the result that I want.
Frans
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I don't know if everybody has agreed on this yet. I'm an engineer and know more than a lot about angles and geometry. I use a DMT aligner and proved to myself long ago that the angle doesn't change along the straight part of the blade. I'll make 2 attempts to explain:
from post #25 this image does a pretty good job of explaining. If the wire frame drawing shows 2 planes, one that is vertical representing the blade and one that is angled representing the primary bevel, and the 2 planes meet at the edge. At the bottom of the angled plane is the pivot point for the sharpening device. As the sharpening device swings along the edge it stays aligned with the plane of the primary bevel.
and now I think this was from post #26- If the distance increases then yes the angle between this line and the edge decreases. BUT, and this is the critical point, THIS IS NOT THE ANGLE THAT WE ARE INTERESTED IN. The angle of the bevel that we always talk about is measured perpendicular to the edge. The line that pivots towards the end of the blade, the line that we are saying the angle of which changes, is no longer perpendicular to the edge. So yes the angle of the line changes, but the bevel angle of the edge does not change.
But most blades are not straight, they have some curved portions, or "belly". A simplified version of this would be an edge with constant radius curve. Connect a guided system to this blade with the pivot positioned at the theoretical center of the curve of the blade and as the sharpening device moves along the edge the distance from pivot to edge will stay the same so the angle doesn't change, and the line of the sharpening is perpendicular to the edge, so everything remains perfect. Take a knife where part of the edge is straight or somewhat straight, and part of the edge is curved, clamp on a guided system, position the system so its pivot is close to the same distance from all parts of the edge, and you will have a good chance of maintaining close to a constant angle along the entire edge. If there is a long straight part with a curve near the ends, something like a Becker BK9, you would have to clamp the device close to the end of the blade and sharpen what part of the blade you can reach, then move the device closer to the handle and sharpen the rest of the blade. Position the device too far from the tip and try to sharpen the tip and you will have varying angles. When I have clamped the Aligner on a knife such as the Spyderco Manix that has a somewhat uniform curve I try to angle the clamp so its pivot is as close to the center of the curve as I can get. I think I got a fairly uniform angle but the blade thickness changes so the width of the bevel is bigger near the tip.
from post #25 this image does a pretty good job of explaining. If the wire frame drawing shows 2 planes, one that is vertical representing the blade and one that is angled representing the primary bevel, and the 2 planes meet at the edge. At the bottom of the angled plane is the pivot point for the sharpening device. As the sharpening device swings along the edge it stays aligned with the plane of the primary bevel.
and now I think this was from post #26- If the distance increases then yes the angle between this line and the edge decreases. BUT, and this is the critical point, THIS IS NOT THE ANGLE THAT WE ARE INTERESTED IN. The angle of the bevel that we always talk about is measured perpendicular to the edge. The line that pivots towards the end of the blade, the line that we are saying the angle of which changes, is no longer perpendicular to the edge. So yes the angle of the line changes, but the bevel angle of the edge does not change.
But most blades are not straight, they have some curved portions, or "belly". A simplified version of this would be an edge with constant radius curve. Connect a guided system to this blade with the pivot positioned at the theoretical center of the curve of the blade and as the sharpening device moves along the edge the distance from pivot to edge will stay the same so the angle doesn't change, and the line of the sharpening is perpendicular to the edge, so everything remains perfect. Take a knife where part of the edge is straight or somewhat straight, and part of the edge is curved, clamp on a guided system, position the system so its pivot is close to the same distance from all parts of the edge, and you will have a good chance of maintaining close to a constant angle along the entire edge. If there is a long straight part with a curve near the ends, something like a Becker BK9, you would have to clamp the device close to the end of the blade and sharpen what part of the blade you can reach, then move the device closer to the handle and sharpen the rest of the blade. Position the device too far from the tip and try to sharpen the tip and you will have varying angles. When I have clamped the Aligner on a knife such as the Spyderco Manix that has a somewhat uniform curve I try to angle the clamp so its pivot is as close to the center of the curve as I can get. I think I got a fairly uniform angle but the blade thickness changes so the width of the bevel is bigger near the tip.
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An old thread on the geometry:
http://www.bladeforums.com/forums/s...metry-and-Kinematics-of-Guided-Rod-Sharpeners
http://www.bladeforums.com/forums/s...metry-and-Kinematics-of-Guided-Rod-Sharpeners
I Hate to say this - Franz, your opinion are correct - and I was wrong.
Thanks for a nice diskussion
Thomas
Hi Thomas,
Thanks for not being afraid to admit and it was indeed a pleasant discussion. :thumbup:
Frans
Thank you for that explanation. This is where I was hung up.
Thanks Frans!
The really fun work is to identifyed sharpening problems and figure out how to tecnical solve them. Then to make prototypes and test them. That is the job I like most
This attachment are also nice to use when sharpen bellys to get the same edge angle on the belly as on the straight part of the edge. Some knifes and machetes have big bellys. This attachment make it possible to grind diagonal. There is a marking om the guide rod for 28 cm distance between the edge and the pivot point, it makes it veey easy ro keep just rhis distance all the time during sharpening where ever the pivot point are. This picture shows how the pivot point moves back (to the right) to keep the 28 cm distance - and keep the same edge angle as on the straight part of the edge.
Thomas
The really fun work is to identifyed sharpening problems and figure out how to tecnical solve them. Then to make prototypes and test them. That is the job I like most
This attachment are also nice to use when sharpen bellys to get the same edge angle on the belly as on the straight part of the edge. Some knifes and machetes have big bellys. This attachment make it possible to grind diagonal. There is a marking om the guide rod for 28 cm distance between the edge and the pivot point, it makes it veey easy ro keep just rhis distance all the time during sharpening where ever the pivot point are. This picture shows how the pivot point moves back (to the right) to keep the 28 cm distance - and keep the same edge angle as on the straight part of the edge.
Thomas
I think the real key to understanding the fact that the planar angle doesn't change is having the clarification that the stone is free to rotate and slide along the axis of the guide rod. This is the complexity that is hard to envision and that allows the plane to be maintained.
But yes there is some good conversation and some great illustration here. A very pleasant read (from another Engineer... 
)
But yes there is some good conversation and some great illustration here.
A very pleasant read (from another Engineer... )- Status