What's new

Lengthwise convex hone

Thanks for the discussion JPO, i am enjoying it.

when i lift the tang, i would think that both contact points shift equally and neither dotted ones are in play any more. When i lift the tang (keeping spine/edge contact) , havent i just essentially rotated the sphere?

and we are doing an x-stroke right? So the amount of time each set of points would be in contact would be minimal for even wear?

Maybe to sum up though, Is the difference even enough to measure as significant? It could really cause a convex bevel? Wouldnt the sphere have to intercept the grind? Like a concave dished hone?
 
Thanks for the discussion JPO, i am enjoying it.

when i lift the tang, i would think that both contact points shift equally and neither dotted ones are in play any more. When i lift the tang (keeping spine/edge contact) , havent i just essentially rotated the sphere?

and we are doing an x-stroke right? So the amount of time each set of points would be in contact would be minimal for even wear?

Maybe to sum up though, Is the difference even enough to measure as significant? It could really cause a convex bevel? Wouldnt the sphere have to intercept the grind? Like a concave dished hone?
Mark your blade and see. I am not sure if and how much of a difference it makes. I need another scrap blade:)
20210928_210245.jpg
 
Is this a 45° or a lift of the tang?
Yes it is at an angle around 45 deg. I did not intentionally lift or lower the tang.
When i hone my hands sort of develops a mind of its own. You have to adjust to the feedback of your stone. Knowing the variables helps, but if you start to think to much it might be counterproductive.
If the bevel is set properly with a convex hone, when you move on the a finer grit stone you feel the resistance change depending on your angle of attack/skew angle and how you move the razor over the stone.

My point is that you might give up something in pursuit of something else.
What is your motivation for using convex stones?
If the goal is ultimate sharpness, i do think there are equally good results to be had from flat stones.

My motivation was trying to get a good edge on a razor with bad geometry. For me that made honing that particular razor much easier.
Now i am playing with convex coticules. I like coticule edges, but there is just something missing. They get sharp enough, but by playing with different shapes, i have been able to get better edges off these stones. Lately i have been bumping up the sharpness of my coticule edges by doing 5-7 strokes on a flat shapton gs 0.44 m. It seems like i then keep some of the smoothness from the coticule but add some sharpness. I have a Les Lat coticule on the way. Maybe that will add something.
Still i usually prefer a good JNAT edge, and i might replace the shapton for that if i feel like it.

Different edges for different grinds, moods, etc.
 
Thanks for the discussion JPO, i am enjoying it.

when i lift the tang, i would think that both contact points shift equally and neither dotted ones are in play any more. When i lift the tang (keeping spine/edge contact) , havent i just essentially rotated the sphere?

and we are doing an x-stroke right? So the amount of time each set of points would be in contact would be minimal for even wear?

Maybe to sum up though, Is the difference even enough to measure as significant? It could really cause a convex bevel? Wouldnt the sphere have to intercept the grind? Like a concave dished hone?
The problem is that the contact point on the bevel vary from the shoulder to the apex depending on your stroke.
If the stone is 20 ft, and the razor is a 7/8 razor the hollow ground difference at the center of the bevel is only 0.05 micron.
The advantage of this is quickly diminishing if the stroke is not "perfect".
This can also be possible, as have been mentioned by stefan by playing with the torque/pressure on a flat stone.
 
I got a deflection of 4 micron in my simulation that is not very scientific at all.

I used this input:

Hollow razor 0,2mm thick all way about 2/3 of the width before getting thicker to the spine
Material: Carbon steel (no specifik)
Load: 15*9,82/1000 (15g) a straight razors weight with plastic scale this size could be about 55g. I used a scale and had the spine outside in similar height and then let the bevel contact the scale and got 15g. Think finishing stroke, not bevel setting.
Load distribution: even distributed on the bevel. This is not correct as not all of the bevel will contact perfectly and the bevel
is likely to be wider than the theoretical in 3D model because of deflection.

4 micron nedböjning.GIF
 
Last edited:
After some evaluation I believe the load is more likely to be half the above and then got 2 micron deflection instead.
 
Some simple honing tests on flat stones with marker pen.

Honing: bevel set and progressing to 5000# and diminishing pressure/torque during progression as usual.
IMG_1893.JPG
But at 5000# stopping before the lighter strokes in the end and mark the bevel with marker pen.

Take some USB pictures at specific points to show the bevel.
Marking the bevel with marker pen again.
Adding 5 very light strokes on each side (normally I would work longer with light pressure).
New USB pictures to see if contact with bevel seems different.

Front side of blade line1. Left picture pre and right picture post light strokes.
1.jpg1B.jpg
Front side of blade line6. Left picture pre and right picture post light strokes.
6.jpg6B.jpg

Back side of blade lineG. Left picture pre and right picture post light strokes.
G.jpgG2.jpg

Back side blade lineF . Left picture pre and right picture post light strokes.
F.jpgF2.jpg


Indication:
Initially there will be refinement wherever material is "above level".
Then refinement initially will be more on the lower half of the bevel area closer to the apex.
I have lower torque/load on my back side of the blade doing finishing strokes.

What's your experience?
 
I got a deflection of 4 micron in my simulation that is not very scientific at all.

I used this input:

Hollow razor 0,2mm thick all way about 2/3 of the width before getting thicker to the spine
Material: Carbon steel (no specifik)
Load: 15*9,82/1000 (15g) a straight razors weight with plastic scale this size could be about 55g. I used a scale and had the spine outside in similar height and then let the bevel contact the scale and got 15g. Think finishing stroke, not bevel setting.
Load distribution: even distributed on the bevel. This is not correct as not all of the bevel will contact perfectly and the bevel
is likely to be wider than the theoretical in 3D model because of deflection.

View attachment 1336500
If you somehow manage to calculate the load you need to lift the apex of the stone, how would you apply that when your honing?
If you want to play with these types of simulations i think you need to set up the model differently. As you apply load to your bevel plane, in reality the resultant force will travel up to the shoulder of you bevel. You would need to use a contact surface with contact elements, which mimics the hone surface. The mesh would also be super fine to get meaningful results. The deflection of the bevel is dependent on the flexibility of the hollow grind. The load should be applied as torque or a load acting at the center of our hollow grind. The contact will then give you the correct reaction force along the bevel plan. The bevel will then act as a fulcrum.

You can also see how the stabilizer complicates things.
 
Some simple honing tests on flat stones with marker pen.

Honing: bevel set and progressing to 5000# and diminishing pressure/torque during progression as usual.
View attachment 1336723
But at 5000# stopping before the lighter strokes in the end and mark the bevel with marker pen.

Take some USB pictures at specific points to show the bevel.
Marking the bevel with marker pen again.
Adding 5 very light strokes on each side (normally I would work longer with light pressure).
New USB pictures to see if contact with bevel seems different.

Front side of blade line1. Left picture pre and right picture post light strokes.
View attachment 1336732View attachment 1336733
Front side of blade line6. Left picture pre and right picture post light strokes.
View attachment 1336744View attachment 1336745

Back side of blade lineG. Left picture pre and right picture post light strokes.
View attachment 1336749View attachment 1336750

Back side blade lineF . Left picture pre and right picture post light strokes.
View attachment 1336754View attachment 1336755


Indication:
Initially there will be refinement wherever material is "above level".
Then refinement initially will be more on the lower half of the bevel area closer to the apex.
I have lower torque/load on my back side of the blade doing finishing strokes.

What's your experience?
I think you will have issues with your approach if you use a razor with a stabilizer. The last photo, which assume is a section close to the stabilizer, seems to be to stiff to be able to flex without doing damage to the apex. It seems like the apex have seen excessive force and as a result more damage then the other sections.

Why not just try a convex hone? It took me less then 10 min to shape one of my coticules, without any concave shaping thingy:)
In principal you only need one stone for this to set the bevel in a controlled manner.
 
I think you will have issues with your approach if you use a razor with a stabilizer. The last photo, which assume is a section close to the stabilizer, seems to be to stiff to be able to flex without doing damage to the apex. It seems like the apex have seen excessive force and as a result more damage then the other sections.

Why not just try a convex hone? It took me less then 10 min to shape one of my coticules, without any concave shaping thingy:)
In principal you only need one stone for this to set the bevel in a controlled manner.

Sorry for not being clear with the pictures.

The darker area in picture to the right is black colour from marker pen not being honed away during 5 very light strokes.
What looks like beat up apex is left over from the marker pen.

Compare the right picture with the left, all darker areas on the right compared to the left are leftover from marker pen.
 
Sorry for not being clear with the pictures.

The darker area in picture to the right is black colour from marker pen not being honed away during 5 very light strokes.
What looks like beat up apex is left over from the marker pen.

Compare the right picture with the left, all darker areas on the right compared to the left are leftover from marker pen.
I still do not understand how you will be able to flex the blade near the stabilizer without issues. Maybe it could be done with a razor like the Bismarck without a stabilizer.
I was not referring to the right picture. The left picture clearly shows a more rounded apex, and not an even transition to the bevel shoulder.
In my opinion this is not going to work if the razor has a stabilizer. You will just dig more into the stone.
 
I want to test convex hone but no hurry at all. Don't believe I get better shaving edges than I get now for my preferences.
Getting supeb edges already for my preference. But I might end up with finding a use for convex hones.

"I think you will have issues with your approach if you use a razor with a stabilizer. The last photo, which assume is a section close to the stabilizer, seems to be to stiff to be able to flex without doing damage to the apex. It seems like the apex have seen excessive force and as a result more damage then the other sections".
-Not sure what you mean. I'm just honing a straight with a stabilizer. The "lineF" is in the middle of the blade. Closer to the shoulder the width of bevel is more narrow.


"I still do not understand how you will be able to flex the blade near the stabilizer without issues. Maybe it could be done with a razor like the Bismarck without a stabilizer.
I was not referring to the right picture. The left picture clearly shows a more rounded apex, and not an even transition to the bevel shoulder. In my opinion this is not going to work if the razor has a stabilizer. You will just dig more into the stone".
- Don't get much out of this. What is a bevel shoulder?

The pictures were not for hard studying the apex but the width of the bevel. So when taking pictures it was important to me that the area above the bevel was visible and I did not care much about the apex itself.
 
I have honed two extra hollow ground razors lately with convex stones. I am not getting good results. It seems like the bevel gets to thin. You do not have enough support behind the edge to be able to refine the edge. I think the sweet spot is with these "normal" full hollow ground razors with good steel. I honed a new 6/8 TI razor, which did take a really good edge.

This razor would probably take a good edge with a normal progression to, but this is not a 100% straight blade.
I did want to preserve the look of the razor, and was not prepared to force it to make contact on a flat stone all the way from bevel set to finish.
 
If you somehow manage to calculate the load you need to lift the apex of the stone, how would you apply that when your honing?
If you want to play with these types of simulations i think you need to set up the model differently. As you apply load to your bevel plane, in reality the resultant force will travel up to the shoulder of you bevel. You would need to use a contact surface with contact elements, which mimics the hone surface. The mesh would also be super fine to get meaningful results. The deflection of the bevel is dependent on the flexibility of the hollow grind. The load should be applied as torque or a load acting at the center of our hollow grind. The contact will then give you the correct reaction force along the bevel plan. The bevel will then act as a fulcrum.

You can also see how the stabilizer complicates things.


"If you somehow manage to calculate the load you need to lift the apex of the stone, how would you apply that when your honing"?
-No.
Before the second simulation I put the straight razor blade on a scale that I hold in my hand just as honing.
The weight the scale then showed was actually less than the weight of the razor, about 28g ( razor 55g).
I did some very light honig strokes on the scale(steel) and got 24g( 20-30).
I then just made an estimate that 1/3 of the load was through the bevel.
Not very scientific. But then consider that mid bevesetting( from start, not you that buy shave ready Dovo) the load mid progression might be about 130g achieved with heavier torquing than why perhaps half load from 130g is through the bevel.

"If you want to play with these types of simulations i think you need to set up the model differently. As you apply load to your bevel plane, in reality the resultant force will travel up to the shoulder of you bevel".
-When I do or watch a simulation the simulation itself should tell me this. Not vice versa.

Where there is a shoulder of course it will take load. If I also put in geometry corresponding to a shoulder's mid blade and one also in the toe area, then yes. But now we have something looking more like a wedge.

"You can also see how the stabilizer complicates things".
-It change things.

"The load should be applied as torque or a load acting at the center of our hollow grind. The contact will then give you the correct reaction force along the bevel plan. The bevel will then act as a fulcrum".
- In a simple simulation there will be load from the blade/razor weight and a torque via the shank because of the honer's grip on the shank and scale. The honer can also add a pressure downwards( or any directions).
The hone will respond with a reaction force up to the spine and also one on the bevel.
It is the reaction force on the bevel that makes the blade deform "width wise".
It creates a torque with the spine contacting the hone as a pivot line.

"You would need to use a contact surface with contact elements, which mimics the hone surface. The mesh would also be super fine to get meaningful results. The deflection of the bevel is dependent on the flexibility of the hollow grind"
-Not meaningful compared to your calculations?

It would be really interesting. But that's a more advanced simulation.
Below another simple simulation but this time with a narrow hone, 2cm and same presse but only above honearea contacting the bevel( less load) and deformation 0,9 micron.

0,9 micron nedbjning.GIF
 
They all have a different radius. I start with a small radius and transition to a bigger radius, ending on a flat stone.
The key is the bevel shaping stone.

I think if you have only played with stone of say 20 ft, you are missing out. The edge does feel different. You will not figure this out behind a keyboard, you need to get your feet wet:)


View attachment 1335720View attachment 1335721

was just thinking about the math behind the discussion and the difference in that i am using all similar convexed hones vs your progression of larger curvature to flat.. i'm having a hard time fully imagining the space in 3D on a sphere as you turn the razor vs the sphere and the stroke against it. perhaps this thread is not the correct place for this discussion as it looks like there is a couple convos going on simultaneously.
 
was just thinking about the math behind the discussion and the difference in that i am using all similar convexed hones vs your progression of larger curvature to flat.. i'm having a hard time fully imagining the space in 3D on a sphere as you turn the razor vs the sphere and the stroke against it. perhaps this thread is not the correct place for this discussion as it looks like there is a couple convos going on simultaneously.
I agree. All i know is that my practical experience seem to be supported by the theory. I have shaved side by side with a feather pro super and some edges honed with a series of convex hones and the result was in favor of the honed edges. I think i am done trying to convince people who have not invested any time trying to understand this. The message seems to be to learn how to hone.
 
Top Bottom