Have You Ever Rounded Over an Edge Stropping?

[AHill]

I hear this all the time from experts and non-experts all the time when referring to stropping.  You press too hard, and you risk rounding over your edge and losing sharpness in the process.  Then I see Paul Sellers' hard pressure stropping technique on his chisels (at least 25 strops pressing really hard) and wonder if there's really an issue.  At the other extreme, I've seen knife sharpening videos where there's so little pressure, it's hard to believe the strop is providing any benefit whatsoever.  Has anyone actually experienced a rounded over edge?  How could you tell it was rounded over? 

Truth in lending - I've used Sellers' method and found my chisels get VERY sharp when stropped this way straight off a 4000 grit stone.

[barryvabeach]

I found this experiment on stropping , https://youtu.be/-JGLygqjSfE  and have switched over to his method in the last few weeks, and it seems to work.    His test seems to support that leather will not get the blade as sharp as a stone, and so I am using a .03 lapping film on a ceramic tile, and can duplicate his cutting of a piece of copy paper when done.

[ChuckHill]

I found this experiment on stropping , https://youtu.be/-JGLygqjSfE  and have switched over to his method in the last few weeks, and it seems to work.    His test seems to support that leather will not get the blade as sharp as a stone, and so I am using a .03 lapping film on a ceramic tile, and can duplicate his cutting of a piece of copy paper when done.

That is a very, very interesting video.  I wonder if the results would have been the same with the LV green compound or the Flexcut yellow?  And I just bought a new strop...

[AHill]

I found this experiment on stropping , https://youtu.be/-JGLygqjSfE  and have switched over to his method in the last few weeks, and it seems to work.    His test seems to support that leather will not get the blade as sharp as a stone, and so I am using a .03 lapping film on a ceramic tile, and can duplicate his cutting of a piece of copy paper when done.

Interesting video.  For sure, he's rounded over the edge using the strop.  A few observations:

Tormek claims PA-70 stropping compound averages 8000 grit (3 microns).  Other websites claim anywhere from 3000 to 6000 grit.  I was not able to determine what abrasive Tormek uses.  He commented he likes the Tormek paste because "it cuts faster" which is a clue that it's more aggressive compared to the waterstone.  It's also not clear what the particle size distribution is with the PA-70.  Could be there are a lot of coarser grit particles which result in the more aggressive cutting.  PA-70 is similarly priced to the Veritas Green Honing compound.  I'm guessing the green stick lasts a lot longer than a tube of PA-70.

I noticed in his closeup of stropping where he shows the leather "squishing", he actually lifts up the back of the bevel ever so slightly, which could be one reason for the edge rounding over.  To me, that's a very thick and squishy leather strop - and I think that's the primary cause of his edge rounding over when stropping.  My stops are horse butt, which is a very stiff leather, but also much thinner than the strop used in the video.  Suman applies the paste to the smooth side of the strop.  I think most stroppers apply honing compound to the rough side, since it holds the compound better.  (In my knife sharpening setup, I apply diamond paste to the smooth side of a strop.)  Paul Sellers, who strops with a lot of downward force, uses a very flexible strop, but it's also very thin.  He stretches the leather when attaching it to a plywood strop base, held in place with thin double-sided tape.

One other curiosity.  Suman's using a bevel up plane.  While there is a significant difference between the stone and the strop, I wonder whether the same experiment using a bevel down plane would yield the same or similar results.  In a bevel up plane, rounding over an edge is like putting a higher microbevel, which will result in a higher force to plane.  If it were a bevel down plane, the rounding over may not have the same effect, since the edge is always presented at the same angle to the wood.  A rounded over edge on a bevel down plane would provide a greater relief angle when planing.

[Timberwolf]

Interesting video.  For sure, he's rounded over the edge using the strop.  A few observations:

Tormek claims PA-70 stropping compound averages 8000 grit (3 microns).  Other websites claim anywhere from 3000 to 6000 grit.  I was not able to determine what abrasive Tormek uses.  He commented he likes the Tormek paste because "it cuts faster" which is a clue that it's more aggressive compared to the waterstone.  It's also not clear what the particle size distribution is with the PA-70.  Could be there are a lot of coarser grit particles which result in the more aggressive cutting.  PA-70 is similarly priced to the Veritas Green Honing compound.  I'm guessing the green stick lasts a lot longer than a tube of PA-70.

I noticed in his closeup of stropping where he shows the leather "squishing", he actually lifts up the back of the bevel ever so slightly, which could be one reason for the edge rounding over.  To me, that's a very thick and squishy leather strop - and I think that's the primary cause of his edge rounding over when stropping.  My stops are horse butt, which is a very stiff leather, but also much thinner than the strop used in the video.  Suman applies the paste to the smooth side of the strop.  I think most stroppers apply honing compound to the rough side, since it holds the compound better.  (In my knife sharpening setup, I apply diamond paste to the smooth side of a strop.)  Paul Sellers, who strops with a lot of downward force, uses a very flexible strop, but it's also very thin.  He stretches the leather when attaching it to a plywood strop base, held in place with thin double-sided tape.

One other curiosity.  Suman's using a bevel up plane.  While there is a significant difference between the stone and the strop, I wonder whether the same experiment using a bevel down plane would yield the same or similar results.  In a bevel up plane, rounding over an edge is like putting a higher microbevel, which will result in a higher force to plane.  If it were a bevel down plane, the rounding over may not have the same effect, since the edge is always presented at the same angle to the wood.  A rounded over edge on a bevel down plane would provide a greater relief angle when planing.

........................
Hand stropping is so....yesterday.....
...Learn to power strop CORRECTLY on leather or muslin and use the time saved for working wood or watching Sellers on Youtube.. Do it correctly and you may never need to hone again.

[stav]

........................
Hand stropping is so....yesterday.....
...Learn to power strop CORRECTLY on leather or muslin and use the time saved for working wood or watching Sellers on Youtube.. Do it correctly and you may never need to hone again.

So when are you going to sell these things or plans for them?

[Timberwolf]

So when are you going to sell these things or plans for them?

......................
Coming up on 91years, Stav..so no plans to make any more and no plans really needed..I can post photos and anyone who wants to can make them out of really hard wood or aluminum using ordinary woodworking tools..A bandsaw and wood lathe will make it easier.  There are instructions on making similar machines out of wood,  posted on Youtube..but aluminum can easily be cut on a BS using woodworking blades.

People living near Orlando can usually find scrap aluminum at Skycraft Surplus not far off the Interstate. They frequently have electric motors but you can almost always find them on Facebook Marketplace..1/4HP..1725RPM motors are powerful enough....This one runs at about 1,000fpm belt speed...A good skateboard wheel can be adapted to serve as an Idler wheel...A 2" diameter hole saw can cut a plug that can be used as the drive wheel...just bore the center hole to fit the motor shaft diameter and use epoxy to glue it on the shaft...then turn the motor on and use it as a lathe to crown the wheel and make it run true..Leave the motor loose so as the adjust tracking then lock it down..Belt tracking adjustment will not be needed once good tracking is established.

Caution...Many guys become addicted on their first visit to Skycraft..Leave your credit card at home...I have been trying to escape the addiction for nearly fifty years but it's a good thing I am over 100 miles away from it!!!!!!!

[bandit571]

Use the Unicorn?
[attachment=47460]
Have yet to "round-over" an edge with it...

[Timberwolf]

Use the Unicorn?

Have yet to "round-over" an edge with it...

.....................
Yep....Unicorn before it was ever given a name...

[barryvabeach]

I

One other curiosity.  Suman's using a bevel up plane.  While there is a significant difference between the stone and the strop, I wonder whether the same experiment using a bevel down plane would yield the same or similar results.  In a bevel up plane, rounding over an edge is like putting a higher microbevel, which will result in a higher force to plane.  If it were a bevel down plane, the rounding over may not have the same effect, since the edge is always presented at the same angle to the wood.  A rounded over edge on a bevel down plane would provide a greater relief angle when planing.

I agree with your observation, but I think in his testing, he is testing the sharpness of the blade using a testing jig - which tests the blade outside of the plane body, so bevel up or down should not make a difference in the sharpness he is measuring.   BTW,  I have also switched over to using his method of testing using copy paper, and yes, some of my blades did not cleanly cut it until I went back and honed at .3 micron film.