Cliff Stamp
BANNED
- Joined
- Oct 5, 1998
- Messages
- 17,562
While recently comparing a few steeling devices I had a chance to examine the edges of extensively blunted knives [down to 5-10% of optimal sharpness] before and after steeling which allowed me to check exactly what was happening to the knife to restore the edge. I checked the edges under magnification from the side as well as straight down into the edge. Nothing really surprising resulted, but some quantification to what was before just a lot of guessing and hypothesis formation. The effects are :
1) Removal of large lateral dents and deformations, damage depth up to 100 microns. After cutting a lot of heavy cardboard (30+m of 1/8" ridged, sides were a full one mm thick and stiff), there were lateral dents in the edges of the knives, from 50 to 100 microns wide. Cutting a similar amount of lighter cardboard (same thickness, softer/thinner sides), the side dents were much smaller. Slicing 100+ pieces of hemp rope, the dents were smaller again, now only 5-10 microns. After using a smooth steel (just a few passes per side), the dents were gone, the edge was now straight.
2) Removing of impaction and rolling from the very edge, damage depth was just a few microns. When looking at the above dulled edges straight on, not only are the large side dents visible, but there is heavy reflection of light from the edge, showing that it is significantly impacted and rolled (with some wear as well). You can't see this effect from the side. After steeling, there is very little reflection from the edge, showing that it comes basically to a point as it should.
3) A smearing out of the edge making it more acute. I tested edges that were freshly honed (coarse as well as polished on various hones), and a few passes on a smooth steel after honing did in fact make them sharper. However there are downsides to this process. First you can sway the edge to one side if you are not careful. Second you are weakening the edge and it will blunt faster. A couple of passes on plain leather or canvas loaded with chalk paste will also improve final sharpness, by cleaning the edge of debris and doing a light alignment plus polish (getting rid of stragglers in jagged cuts), without weakening the edge.
So there are two main processes, and both of them are essentially aligning the edge back to straight - nothing new there, but it was nice to actually see it first hand. The third one is usually a small effect unless you overdue it.
As a side note, the common belief that steeling with a slick or smooth steel, removes no metal is false. I believe this point was first contested by Alvin Johnson on rec.knives some years ago. You can clearly see under magnification that the contact areas on the edge are burnished and not just moved. You can also see grind lines on "smooth" steels if you look under high enough magnification, they are not visible by eye, nor can you feel them. Wear by abrasive (grind lines induce essentially microscopic filing) and adhesion (metal on metal pseudo-welding) is taking place. Of course the metal wear is very small compared to a ceramic or diamond "steel" . You can also clean metal debris from heavily used smooth steels. I checked a few that were multiple years old. The latter point is debatable, though as you could be just seeing dirt build up. You could check it easily by doing a *lot* of steeling in a short period of time and checking the surface, or having the debris tested. John Juranitch has also had edges examined under high magnification (3000X), and it is clearly visible that steeling removed scratches left from the finishing hones.
A couple of questions/points of interest :
1) If you use a diamond "steel" on a heavily damaged edge such as described in the above (~100 micron dents). Will this "steel" just cut the dents off and leave pock marks in the edge, or does it align it at the same time?
2) Depending on the answer to the above, is there any benefit to a light steeling on a smooth steel (~1 - 2 passes), or very fine ceramic for just alignment, before you use a diamond "steel" if that is your preferred finish. I have done this on occasion as it made sense to me, but never actually checked it out, intend to do so.
3) Does steeling actually prolong the life of an edge as compared to using a ceramic or diamond "steel" (or whatever hone you prefer). Doing some testing with some utility knives on cardboard showed that this isn't always the case. Frequent light steeling to restore the edges tended to induce chipping over time as the edge was over weakened. The amount of metal lost in removing the induced chips was comparable to what would have been lost if a ceramic or diamond rod had been used instead. This of course is dependent on what the knife is cutting, on flesh and vegetables, this doesn't happen. So this point is not as trivial as it is sometimes described. Not to mention the side effect that steeled edges don't have anywhere near the edge retention of freshly honed edges.
4) Do butchers steels really "destroy" finely honed edges? This isn't trivial either. It depends on the hardness of the knife edge and how hard you are pressing it into the steel. Using a 62 RC D2 blade on butcher steel and pressing hard I broke the edge apart resulting in degraded performance and increasing the necessary amount of honing to remove the chips. Using it lightly this wasn't a problem. Using it very hard on a softer knife [Henckels paring knife] resulted in a filed edge, which has the disadvantages and advantages of a coarse edge. It can also preserve fine edges if you go very light. Some more work is needed here, basically just do the above checking under magnification again comparing it so a smooth steel.
5) Is there any point to a Butchers steel when you have ceramic / diamond rods of various grits? A point Mike Swaim brought up some time ago. Pretty much the main advantage is that the steel will preserve the edge finish where as the rods will induce their own, but a smooth steel will do this as well without the risk of damage due to too much pressure which you risk with a grooved steel. So what are the properties of a butchers steeled edge for the final finish (using it as a file), as compared to a suitable ceramic or diamond rod? Or can grooved steels align edges that are too damaged for smooth steels? Do the steeled edges differ in cutting ability or edge retention (smooth vs grooved)? Lots of questions.
[the bulk of the work mainly draws on recent experience with Olfa utility blades, but I have done similar cutting with many other knives, production and custom]
-Cliff
1) Removal of large lateral dents and deformations, damage depth up to 100 microns. After cutting a lot of heavy cardboard (30+m of 1/8" ridged, sides were a full one mm thick and stiff), there were lateral dents in the edges of the knives, from 50 to 100 microns wide. Cutting a similar amount of lighter cardboard (same thickness, softer/thinner sides), the side dents were much smaller. Slicing 100+ pieces of hemp rope, the dents were smaller again, now only 5-10 microns. After using a smooth steel (just a few passes per side), the dents were gone, the edge was now straight.
2) Removing of impaction and rolling from the very edge, damage depth was just a few microns. When looking at the above dulled edges straight on, not only are the large side dents visible, but there is heavy reflection of light from the edge, showing that it is significantly impacted and rolled (with some wear as well). You can't see this effect from the side. After steeling, there is very little reflection from the edge, showing that it comes basically to a point as it should.
3) A smearing out of the edge making it more acute. I tested edges that were freshly honed (coarse as well as polished on various hones), and a few passes on a smooth steel after honing did in fact make them sharper. However there are downsides to this process. First you can sway the edge to one side if you are not careful. Second you are weakening the edge and it will blunt faster. A couple of passes on plain leather or canvas loaded with chalk paste will also improve final sharpness, by cleaning the edge of debris and doing a light alignment plus polish (getting rid of stragglers in jagged cuts), without weakening the edge.
So there are two main processes, and both of them are essentially aligning the edge back to straight - nothing new there, but it was nice to actually see it first hand. The third one is usually a small effect unless you overdue it.
As a side note, the common belief that steeling with a slick or smooth steel, removes no metal is false. I believe this point was first contested by Alvin Johnson on rec.knives some years ago. You can clearly see under magnification that the contact areas on the edge are burnished and not just moved. You can also see grind lines on "smooth" steels if you look under high enough magnification, they are not visible by eye, nor can you feel them. Wear by abrasive (grind lines induce essentially microscopic filing) and adhesion (metal on metal pseudo-welding) is taking place. Of course the metal wear is very small compared to a ceramic or diamond "steel" . You can also clean metal debris from heavily used smooth steels. I checked a few that were multiple years old. The latter point is debatable, though as you could be just seeing dirt build up. You could check it easily by doing a *lot* of steeling in a short period of time and checking the surface, or having the debris tested. John Juranitch has also had edges examined under high magnification (3000X), and it is clearly visible that steeling removed scratches left from the finishing hones.
A couple of questions/points of interest :
1) If you use a diamond "steel" on a heavily damaged edge such as described in the above (~100 micron dents). Will this "steel" just cut the dents off and leave pock marks in the edge, or does it align it at the same time?
2) Depending on the answer to the above, is there any benefit to a light steeling on a smooth steel (~1 - 2 passes), or very fine ceramic for just alignment, before you use a diamond "steel" if that is your preferred finish. I have done this on occasion as it made sense to me, but never actually checked it out, intend to do so.
3) Does steeling actually prolong the life of an edge as compared to using a ceramic or diamond "steel" (or whatever hone you prefer). Doing some testing with some utility knives on cardboard showed that this isn't always the case. Frequent light steeling to restore the edges tended to induce chipping over time as the edge was over weakened. The amount of metal lost in removing the induced chips was comparable to what would have been lost if a ceramic or diamond rod had been used instead. This of course is dependent on what the knife is cutting, on flesh and vegetables, this doesn't happen. So this point is not as trivial as it is sometimes described. Not to mention the side effect that steeled edges don't have anywhere near the edge retention of freshly honed edges.
4) Do butchers steels really "destroy" finely honed edges? This isn't trivial either. It depends on the hardness of the knife edge and how hard you are pressing it into the steel. Using a 62 RC D2 blade on butcher steel and pressing hard I broke the edge apart resulting in degraded performance and increasing the necessary amount of honing to remove the chips. Using it lightly this wasn't a problem. Using it very hard on a softer knife [Henckels paring knife] resulted in a filed edge, which has the disadvantages and advantages of a coarse edge. It can also preserve fine edges if you go very light. Some more work is needed here, basically just do the above checking under magnification again comparing it so a smooth steel.
5) Is there any point to a Butchers steel when you have ceramic / diamond rods of various grits? A point Mike Swaim brought up some time ago. Pretty much the main advantage is that the steel will preserve the edge finish where as the rods will induce their own, but a smooth steel will do this as well without the risk of damage due to too much pressure which you risk with a grooved steel. So what are the properties of a butchers steeled edge for the final finish (using it as a file), as compared to a suitable ceramic or diamond rod? Or can grooved steels align edges that are too damaged for smooth steels? Do the steeled edges differ in cutting ability or edge retention (smooth vs grooved)? Lots of questions.
[the bulk of the work mainly draws on recent experience with Olfa utility blades, but I have done similar cutting with many other knives, production and custom]
-Cliff
