angles on clamp style devices

[EdgePal]

In picture 1, meassure the distance from the top of the liner up to the blue tape. I guess that is about 2"

In picture 2. Follow the direction of the liner and measure the distance up to the blue tape, I guess that is about 4" = 2 " longer distance, this will be around 1,5 - 2 degree differane I think.

Now, put a pencil on the top of the liner and draw a line from side ro side wen you swing the liner. If that line was a edge - you will get the same edge angle on the edge.

This picture shows what I try to explain. My tool Chef sharpens a curved edge and this edge curve fits perfect in distance from the pivot point.

Thomas

 

[fvdk]

In picture 1, meassure the distance from the top of the liner up to the blue tape. I guess that is about 2"

In picture 2. Follow the direction of the liner and measure the distance up to the blue tape, I guess that is about 4" = 2 " longer distance, this will be around 1,5 - 2 degree differane I think.

Man, you really don't get it. The ruler in my picture is just 30 cm long but if it would be longer, for example 2" or any other length where it would touch the blue tape, representing the knife edge, it would still lay flat on the box and the edge angle would still be the same.

In your example, the blade is curved and than the angle changes just as it would change in my example if the knife would have a curved tip because the edge than enters another plane.
I hope you will have an Eureka moment and get it but if not than fine, we will than have to agree to disagree because I can not make it any clearer.

Frans

 

[EdgePal]

No my friend, you are wrong. If the distance between the edge and the pivot point change - the angle also change. You cannot come around that.

If you have a knife with a short blade and a normal medium belly - perhaps the distance will not change when you sharpen the blade. But this will be rare.

Then, do this small changes on small blades really matter? No, they do not matter in my opinion. On longer blades, they do matter for precision nerds like me

If the distance between the pivot point and the edge is short, this change of the angle will be big. If the distance is long, the change will be small. A Lansky, Gatco, DMT Alinger and EdgePal Basic holds around 10-12 cm distance between the pivot point and the edge - and you cannot sharpen a knife longer then 12 cm blade length with those tools, above 12 cm blade length this change if the angle will be to big.

Edge Pro, Wicked Edge, EdgePal Forest, have around 15-17 cm distance between the edge and the pivot point, this gives a blade length on around 18 cm as max (if the blade are fixed in position on the grinding table).

EdgePal Chef have 28 cm distance between the edge and the pivot point, the change in angle on a 25 cm long blade is then 0,2 degrees on the tip of the blade and close to the handle.

If you put a 25 cm long blade in for example a Lansky - the change on the edge will be many degrees...

In my mind, this is important to understand by all people that are interested in shapening, this is basic knowledge.

It feels wrong to stop "arguing" about this, the principle are important to understand.

I invent and construct sharpening tools. When I do that, this is very important to understand - and a big part in my constructions and designs. That is also why I work with longer distances between the dge and the pivot point then other toolmakers do.

In Scandinavia we use edges around 20 degrees total edge. A Mora knife normally hold 22 degree total edge. Our whittling knifes holds 18-19 degree total edge. Degrees are important for us. In US the edges often holds 40 degrees total edge. 1-2 degree change do not really matter on edges in higher angles. We use 35-40 degrees on our felling axes. For a whittling knife 1 degree is a big change...

If you have a Lansky or similar, try to clamp the blade close to the handle and then sharpen the complete blade. The result will be a high edge angle where you use the highest force - and a lower edge angle where you use less force. It will be a very good working edge - and you use the fact that the distance between the edge and the pivot point also change the angle. You get someting bad to work for you instead to against you.

Thomas

 

[fvdk]

In my mind, this is important to understand by all people that are interested in shapening, this is basic knowledge.

It feels wrong to stop "arguing" about this, the principle are important to understand.

Try to forget everything you have been saying earlier in this thread and look at my pictures again with a clear and open mind.

The distance of the red dot on the floor (pivot point) to the edge (blue tape) obviously changes along the length of the tape but the angle at which the box is positioned and with it, the ruler and the tape placed upon it does not.

I don't mind arguing about this but I think that my pictures prove it.
The box is 40 cm wide so in this example it proves that the edge does not change for a blade that is between 0 and 40 cm long or for any length as long as it is a straight edge.

Frans

 

[EdgePal]

Frans, i hope you se me as a friend. I se you as a friend. I will also keep you as a friend.

My English is at it is. I have problems to explain things in English becouse i miss many words...

1. If the distance between the edge and the pivot point change - the angle will also change. Can you agree with that?

2. When a knife blade are fixed on, or in, a grinding table or a clamp the nearest part of the edge is just in front of the tool,min the middle of the grinding table, or in the middle of the clamp.

3. When you fo to the left, or right from that point (2) the distance will be longer between the edge and the pivot point.

4. When the distance grows - the edge angle get lower.

Point 1-4 follows the law of physics. Think what you want - but I recomend to not argue against the law of physics.

You have a steel liner. Good. Take a book or similar, put the book on a table close to its end. Lean the liner against the book and the end of the table (the end of the table is the cutting edge). Now you have a angle on the steel liner. Now, move the book (pivot point) closer to the end of the table (the edge) - and you can clearly see that the angle change to a steeper angle. If you move the book back again, the angle will be lower = if the distance between the dge and the pivot point change - the angle also change. You cannot come around that.

If the distance grows only a millimeter - the angle change very little - but there is a change.

I see this with a very clear open mind - and I work with this every day. It is a part if my "ocupation" sins many years back. I am now retaired so this is today only my hobby (I am soon 70).

As I wrote above, my English is like it is.. Perhaps are we speaking of two different things and missunderstand eachother?

Thomas

 

[fvdk]

Hi Thomas, I do see you as a friend and like you, English is not my native language so it is not easy to explain technical and trigonometry principles.

Here are some images I copied from Clay Allison's blog http://tecniques.sharpening.info/2010/08/does-angle-change-along-length-of-blade.html?q=angle+change

I edited the drawing and I hope it makes things clearer.

1. If the distance between the edge and the pivot point change - the angle will also change. Can you agree with that?

If in the picture, the edge would be at another position, for example line C or A would be longer or shorter, than the edge would change and I think that is as you picture it in your mind.

However, once the knife is in a fixed position in the clamp, neither side (A, B or C) of the triangle changes and only the sharpening stone moves along the red lines (pivot arm) and that does not change any of the angles of the edge triangle.

I believe that you think of it like the length of the pivot arm making a change to the edge angle but I hope that at least in this picture you can see that the length of the pivot arm (the red lines) do not make any difference to the edge angle.
The distance of the pivot point to the edge of the knife is not the same as the distance from the base of the sharpener to the edge of the knife (line A in the picture).

The two photo's also show this with an angle cube. The 0.1 degree difference in the two photos are well within the margin of error of the angle cube.

Frans

 

[EdgePal]

Frans, good, we are friends and can discuss friendly

You show 2 pictures, the angle Cube shows 0,1 degree differens. That is ok for me. As I say above, a 25 cm long blade get 0,2 change of the edge angle with my tool Chef.

What I am missing in the drawing you showed is the length of the blade in the drawing. I think that is a very short blade...
Short blades get small changes...

If you have a Wicked Edge, clamp your steel liner in the clamp on 15 cm point in the middle of the clamp. Then you have 15 cm "edge" in both directions from the clamp. Now, meassure the distance with the guide rod. Put it up against the 15 cm mark, put a mark on the guide rod where it means on the "edge". Move the arm along the "edge" - and you will se that the mark you made so not reach up to the edge.

You can also meassure the distance up to the 15 cm mark, then meassure tontye 20 cm mark and 25 cm mark - and those meassures are not the same. This means that the angle also have change, the angle have start to be lower. Id you also meassure the 30 cm mark, you get a even longer distance - and of cause, an even lower angle. You, I, or anyone else can not avoid this.

This small change of the edge angle do not matter for 99,9 % of knife users - but the change is there. Long blades get bigger changes of the edge angle.

The belly of the knife turn backwards. That means that the distance will be shorter between the tip of the edge and the pivot point compare to where the belly bigins.

So we have the liner and your meassures there, where the distance make the edge angle be lower along the "edge" - and a real knife blade where the belly "turns back" against the pivot point. If it is a big belly, you can get the same distance as you got on the 15 cm mark on the liner.

I have tecnical problems with my English... Can you learn Swedish please,mthen can I describe this a lot better...

Thomas

 

[fvdk]

Frans, good, we are friends and can discuss friendly

Even if we would not be friends, we could still discuss friendly

What I am missing in the drawing you showed is the length of the blade in the drawing. I think that is a very short blade...
Short blades get small changes...

The whole point of my argument and the drawing is that it does not matter how long the blade is. As long as it is a straight edge, the angle is constant.

If you have a Wicked Edge, clamp your steel liner in the clamp on 15 cm point in the middle of the clamp. Then you have 15 cm "edge" in both directions from the clamp. Now, meassure the distance with the guide rod. Put it up against the 15 cm mark, put a mark on the guide rod where it means on the "edge". Move the arm along the "edge" - and you will se that the mark you made so not reach up to the edge.

That is exactly what is shown in the two photos. The stones touch the edge of the ruler at different points but the angle is the same.

Similar.... if you would swipe the red lines on the drawing from left to right, they would describe a circle of which the circumference stretches beyond the edge or perhaps I should better say behind the edge. That is why the angle changes at the (curved) tip of the knife or if the knife would have a curved blade. It does not change on the straight edge.

Perhaps it is better to understand if you think of the pivot point as a pivot line, as long as- and parallel to the knife edge. ?
You can than place the pivot point at any place on the pivot line and swipe it across the plane of the knife. The knife edge and pivot line (distance of line A in the drawing) would not change nor would the length of line B and C so all angles of the triangle stay the same.

Frans

If you are ever in the Netherlands, please let me know and we can do some experiments together

 

[EdgePal]

This picture shows what I am talking about.

This is a sort of standing clamp (if the clamp stand up or lay down do not matter). The hight up to the top of the liner are 155 millimeter (mm).

A liner, 30 cm long, are clamped in the middle on the 15 cm mark on the liner. I have drawn 2 pivot points, one in 15 degrees and one in 25,5 degrees.

from the 15 degree pivot point up to the top of the liner on the 15 cm marking is: 159 mm. to the 20 cm marking is: 167 mm, to the 25 cm marking is: 188 mm and to the 30 cm marking is 219 mm. I have also drawn a belly and a tip of a knife blade. To the tip is the distance 205 mm. The edge angle is 15 degrees on the 15 cm marking on the liner. On the other markings the edge angle are lower then 15 degrees depending on that the distance are longer to those points.

From the 25,5 degree pivot point there is a distance up to the top of the liner on the 15 cm mark: 170 mm, then it changes to: 177, 197, and 227 on the 30 cm mark. The tip of the blade have 214 mm distance.

The degrees on the edge (where the pivot point are) do not matter, this rules by the law of physics. you cannot avoid it or go around it - if you have a fixed pivot point.

All sharpening tools work after this principle. EdgePro have a fixed pivot point - but you can move the blade instead of the pivot point - but then the blade is not fixed.

I made also a arc with 159 mm distance from the pivot point. An edge following this arc will get an exactly 15 degrees edge without any changes of the angle.

Lets say that the pivot point can move parallell to the edge (closer to you in this drawing). Then the edge angle do not change at all before you come to the belly. When you come to the belly you move the pivot point back a little to keep the correct distance, (there is a way to do this in a very simple way).

With a moving pivot point anyone can sharpen any edge up to a swords length - and keep the edge angle 100 % the same all along the edge. (I have made a tool with a moving pivot point - just to be able to do just this.

As I wrote above, a short blade gets small changes. If I shall sharpen a Bowie, machete or a sword, the changes in angle will be very big. This is important to understand - in my opinion.

I enjoy precision grinding. My tool Chef can change an edge 1/100 part of 1 degree - and then go between this two surfaces and hit them correctly without changing them. I enjoy this precision. I have now use at all of changing an edge so little - but that is the smallest change I have made with full control of the angle, this means that I can make, for example, 0,25 degrees change also - or any other angle - and that is for me useful. As you se, I am a grinding nerd

I have made this drawing in a program named Sketchup. It is a 3D program. You can download it from Google and it is free. If you like to have the drawing just contact me by PM and I send it to you. if you download Sketchup you can then se this drawing in 3D and see it from any angle. It is a very nice program to work with and simple to learn how to handle. You can also check that all distances are correct.

If you are good in math you can calculate in degrees, or part of degrees, the changes are- now when you have the distances.

Thomas

 

[fvdk]

Just a short answer as it is time to go to bed.

The angle of a knife edge is measured as one of the angles of a triangle (3 dimensions)
In your drawing the standing part is side A (1st dimension), the base of the clamp is side B (2nd dimension) and the line(s) that go from the base to the top of the stand are side C (3rd dimension). The lines that go to the right side are no part of the calculation. A knife is not a cone, you are measuring the wrong dimension (plane).

Frans

 

[bucketstove]

Just a short answer as it is time to go to bed.

The angle of a knife edge is measured as one of the angles of a triangle (3 dimensions)
In your drawing the standing part is side A (1st dimension), the base of the clamp is side B (2nd dimension) and the line(s) that go from the base to the top of the stand are side C (3rd dimension). The lines that go to the right side are no part of the calculation. A knife is not a cone, you are measuring the wrong dimension (plane).

Frans

have you heard of the 1/60 rule of estimating angles?
a rise of 1 mm and a run of 60mm is a 1 degree angle
a rise(height) of 10mm and a run(length) of 60mm is a 10 degree angle

with a lansky type system the rise(height, y-axis) is fixed , its the hole in the clamp,
but the run(length, x-axis) is not fixed (it changes), its the distance from hole to the edge
Play with this you'll we what I'm talking about
keep rise at 15 and change the run, as run gets longer the angle gets lower
rise 15 run 60 opposite angle: 14.036°
rise 15 run 70 opposite angle: 9.462°

 

[fvdk]

with a lansky type system the rise(height, y-axis) is fixed , its the hole in the clamp,
but the run(length, x-axis) is not fixed (it changes), its the distance from hole to the edge
Play with this you'll we what I'm talking about
keep rise at 15 and change the run, as run gets longer the angle gets lower
rise 15 run 60 opposite angle: 14.036°
rise 15 run 70 opposite angle: 9.462°

Yes, of course the angle changes depending on how far the edge of the knife sticks out of the tip of the clamp (or run length as you call it).
However..... during sharpening that length does not change anymore the knife is set a a certain position. The rise (hole in the clamp does not change either.
You can have for example a clamp of 3 cm wide with a 10" long knife in it (like a Lansky clamp) or a 10" wide clamp with a 10" long knife in it. In the last case you would have a very wide hole for the sharpening rod but the sharpening angle will still be the same, no matter where in that wide slot your rod is.

Lets assume for arguments sake that you place 10 Lansky clamps side-by-side and clamp that 10" long knife along all the clamps.
No sharpen the knife in segments at lets say the 20 degree setting using each clamp only for the width of that clamp.

Would you agree that the whole length of the knife is now sharpened at a constant angle of 20 degrees?

Lets now stick one of the rods in the 20 degree hole of the left clamp and let it rest at the edge of the knife of the right clamp.
Measure the angle that the rod now has from that 20 degrees hole down to the edge on the right side. Of course (diagonal sloping angle of the rod is much lower than 20 degrees but now you are measuring something completely different, not the angle of the edge.

Look at the triangle as drawn from the calculator from your example.
Now imagine that it is not a one dimensional triangle as in the drawing but like for example a 3 angular wooden beam with a length of 2 meter.
Your angle b of 14.036° as from your calculation would stay the same along the entire length of the beam.

Frans

 

[bucketstove]

Yes, of course the angle changes depending on how far the edge of the knife sticks out of the tip of the clamp (or run length as you call it)...

Hahaha ...
How far is the TIP of the knife away from the clamp? Its LONGER right than the edge right in front of the clamp? This is the distance.

 

[fvdk]

Hahaha ...
How far is the TIP of the knife away from the clamp? Its LONGER right than the edge right in front of the clamp? This is the distance.

You will have to look at it as if the base of the clamp is as wide as the knife is long.
Over the entire length, the edge of the knife is parallel to the base of the clamp and at the same angle.

Again some photos which might explain a bit better.

You are measuring the angle of the ruler (stone) lengthwise from the hole in the clamp to the edge of the knife but the ruler also rotates around his axis and you should measure the angle sideways.

 

[scamero]

Not having anything to do with the above discussion, but I know my dmt aligner changes angle depending on how much you tighten the blade clamp screw. My KME is up to 2 degrees different from one side to the other depending on how well you center the blade in the clamp, and the clamp pressure. The edgepro wouldn't have this problem, but then you have the knives moving around slightly on the edgepro, which I'm sure changes the angle a little; and you also have to deal with blade flats and/or bevels on the edgepro being different angles. Never tried a wicked edge, but I would guess it would suffer from clamp/blade alignment and clamp pressure issues like the other clamp systems. Basically it's hard to get a good "zero" on all these systems.

 

[fvdk]

Not having anything to do with the above discussion, but I know my dmt aligner changes angle depending on how much you tighten the blade clamp screw. My KME is up to 2 degrees different from one side to the other depending on how well you center the blade in the clamp, and the clamp pressure. The edgepro wouldn't have this problem, but then you have the knives moving around slightly on the edgepro, which I'm sure changes the angle a little; and you also have to deal with blade flats and/or bevels on the edgepro being different angles. Never tried a wicked edge, but I would guess it would suffer from clamp/blade alignment and clamp pressure issues like the other clamp systems. Basically it's hard to get a good "zero" on all these systems.

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.

 

[bucketstove]

ok, if the angle doesn't change, why does lansky warn you about the angle changing?
two fingers is almost an inch, both sides, plus clamp, makes under 3 inches of edge length where the angle doesn't change

If blade is 7” or less in length:

• Position the clamp in the middle of the blade.
• After sharpening, flip the clamp (and blade) over and repeat the sharpening process on the unsharpened side.

If blade is greater than 7” in length:

• Pick the end of the blade where you would like to start sharpening and place the clamp two finger widths away from that end of the blade. (For example, if you choose the tip, place the clamp 2 finger widths from away the tip.)
• When you have the blade secured in the clamp, place your 2 fingers along both sides of the knife clamp. The area covered by your fingers (on both sides of the clamp) is your target sharpening zone. Try not to sharpen outside this zone, as this will change the angle of the hone and result in a poorly sharpened blade.
• Sharpen your target zone, and with the knife still secured in the clamp, flip the clamp (and knife) over and repeat this process on the other side of the blade.
• When you are finished with the first zone on both sides of the blade, measure another two-finger width starting at the edge of your freshly-sharpened area, and place the clamp next to your fingers.
• Sharpen this new target zone as you did the first, roughly using the same number of sharpening strokes.
• Your use of this method will minimize gaps and overlaps between your target zones, helping to ensure a continuous sharp edge when you are finished.

no warning here, as easy as 1-2-3 lansky-sharpening-systems
no warning here, as easy as 1-2-3 lanskysharpeners
no warning here, as easy as 1-2-3 instructions-lansky.pdf
no warning here, as easy as 1-2-3 Lansky_instructions.pdf

and here are two images showing how that works, a top view and a "side" view ... pretty much what EdgePal tried to show you just highlighting the run and angles

 

[cbwx34]

When I first saw the Wicked Edge post a few years back, that the angle doesn't change, I thought, "that's crazy, of course it changes". It's basic trig that most learn... if the distance increases, the angle decreases in a triangle, right?

Long story short, after a bunch of testing, I ended up figuring out, that WE is right. As long as you're in the straight area of the blade, the angle won't change, no matter how far down you go. Take a look at these pictures...

I figured the easiest way to prove WE wrong, was to take an extreme example. So, if you look in the top photo, I took a flat piece of aluminum and mounted it in the WE. Then I took dental floss and from the same point on the angle bar (20 deg I believe, it's been a few years), I attached it to points on the aluminum. If you look at the top photo, it seems obvious that the angle is getting smaller as you go down the "blade" right? But, if you put a stone on the arm, and held it as far out as you could, the relation between the aluminum and the stone didn't change... it still contacted the aluminum at the same angle.

That's when I realized that the angles you see in the top photo are not the angle that the stone is sharpening at. If you take a look at the lower photo... a picture taken sighting down the aluminum, you can see that all the pieces of dental floss line up perfectly. This is the angle the aluminum "sees", and what the stone sharpens at.

To answer the question about the Lansky directions, I think that no-one ever really looked at this before. It just seemed logical that the angle would change, as you move away from the pivot.

I also think that there is some observances that sharpeners mistake for the angle changing. One is, as a knife curve towards the tip, if it's far away from the pivot, the angle can change... this is shown in the WE post. So the assumption is made that it was probably changing the entire length. Another factor... many knives taper as the move toward the tip, even in the straight area you sometimes move into thicker metal, which can result in a wider bevel. So, the assumption is made that the angle changed, even though it's actually a change in the blade. Finally, many blades aren't straight, but have a slight curve, which can change the angle.

The easiest way to test this is to set aside what you think you know is true, like I did, get a long straight knife or even a piece of metal... rig up something that looks like a Lansky or WE, and test it out. When you figure this out, you'll realize that the best way to "set" a knife on a guided sharpener (Wicked Edge, Edge Pro, Lansky, etc.), is not by the length, but by the relationship of the curved area toward the tip. Makes sharpening a lot easier.

Hope this helps!

 

[fvdk]

ok, if the angle doesn't change, why does lansky warn you about the angle changing?
two fingers is almost an inch, both sides, plus clamp, makes under 3 inches of edge length where the angle doesn't change

Really....?

Your post is exactly what I just showed to be wrong in my previous post.

If you would read it well, I fully agreed that the angle of the pivot arm changes as in your drawing but that is the angle as measured across the length of the stone and not the angle at which it sharpens the edge. (you are not trying to digg the very point of the arm into the blade, are you?) The angle at which the stone sharpens is across the other axis of the stone (look again at the photos)

And what don't you understand about the photos with the angle cube showing that the angle does not change, not at two fingers width from the clamp nor at 5" width from the clamp?

And besides that the photos actually show that the Lansky comments are incorrect, the angles as they mark them on the clamp have been wrong since they have been made so measuring or calculating angles is not one of their strong points.

 

[fvdk]

When I first saw the Wicked Edge post a few years back, that the angle doesn't change, I thought, "that's crazy, of course it changes". It's basic trig that most learn... if the distance increases, the angle decreases in a triangle, right?

Long story short, after a bunch of testing, I ended up figuring out, that WE is right. As long as you're in the straight area of the blade, the angle won't change, no matter how far down you go. Take a look at these pictures...

Thank you!

Perfect explanation, l tried but could not have said it better myself

Frans