Ranking of Steels in Categories based on Edge Retention cutting 5/8" rope

chiral.grolim said:
Geez... we need to get Jim a bionic arm or something!

This thing is the closest to WC-Co you can get in steel...

I am very glad it performed well at 15-dps in the full review as well :thumbup: The 0.018" BET makes it suitable for a lot of other utility-purposes, but I can imagine that it was annoying for Jim pushing an edge that much thicker through all the cardboard :eek: I'd be afraid that this steel taken down to 0.005" would fracture massively if the edge ever bound-up in something, given how like it is to cemented carbide...

Another thing i wonder - Maxamet's likeness to WC-Co also lends it to very hot working hardness, i.e. it doesn't lose its temper easily. From the datasheet: http://cartech.ides.com/datasheet.aspx?i=103&e=84&c=techart



It is important to recognize that the carpenter test uses 1000'F/500'C specifically because a number of studies have shown this to be ABOVE the maximum temperature transferred to the cutting tool or work-piece during typical power-grinding dry (no coolant or lubrication). I have many times questioned assertions that power-sharpening (which isn't generally capable of getting anywhere even close to 500'C) necessarily generates sufficient heat to affect edge-temper - particularly since that would mean that cutting alot of cardboard would have the same affect - but here is a case where it wouldn't even matter :cool:
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I wonder about this. It would of course vary some with the metal but the lowest temperature that starts to show red (black red) is listed as 426-593c. I have observed a piece have moments of red while being power ground which does indeed suggest the temper could be affected. One would be hard pressed to generate red heat hand cutting cardboard but I suppose a motivated cutter could possibly raise a little smoke. I'm no expert but is seems that during mass production dry sharpening it would be possible for even the experienced mill worker to allow a little to much friction and bring the temperature up to black red, if only briefly. That would certainly explain why some new blades need several sharpenings to cut away the heat damaged edge.
 
captjlw said:
I wonder about this. It would of course vary some with the metal but the lowest temperature that starts to show red (black red) is listed as 426-593c. I have observed a piece have moments of red while being power ground which does indeed suggest the temper could be affected. One would be hard pressed to generate red heat hand cutting cardboard but I suppose a motivated cutter could possibly raise a little smoke. I'm no expert but is seems that during mass production dry sharpening it would be possible for even the experienced mill worker to allow a little to much friction and bring the temperature up to black red, if only briefly. That would certainly explain why some new blades need several sharpenings to cut away the heat damaged edge.
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http://manufacturingscience.asmedigitalcollection.asme.org/article.aspx?articleid=1447963
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392002000200016
http://wumrc.engin.umich.edu/wp-con...ocouple_fixation_method_for_grinding_temp.pdf

Above are a few publications regarding grind-zone temps in work-pieces, all of which test dry-grinding and show a MAXIMUM temperature to be 500'C. It is noteable that the papers also mention the following:

The cooling properties of the cutting fluids can be neglected and don't cause any improvement in the reduction of the grinding zone temperature and in prevailing compressive residual stresses.
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Grinding experiments and heat transfer analyses showed that grinding fluids provide negligible cooling within the grinding zone.
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The primary reason for using these liquids at all is their lubricity (reducing friction) and to wash away swarf that can clog the abrasive and cause irregular grinding.

When you see "red", what is it that is becoming red? The edge of the knife, or the abrasive itself, or the swarf on the abrasive? Those are 3 different things. Similarly, when there is smoke, what is smoking? I power sharpen, and not even my lawn-mower blades smoke BUT I certainly throw sparks and a clogged belt can start to burn - that is NOT the edge burning, it is the extraneous material.

Primary reason that "new blades" need to be sharpened again soon after use = initial apex was ground too thin or has a burr, or was not fully sharpened in the first place. BIG difference between a properly sharpened apex and one that is just "sharp enough" like we see from most production companies. "Burned" edges remains a theory. Not that you CANNOT burn an edge, but there is no reason to suspect it to be common. Hand-sharpening, the sharpener is usually more meticulous about getting the "perfect" edge.

When i cut cardboard, my knife edge easily gets hotter (and stays hot longer) than when i power-sharpen, and I am by no means an "experienced mill worker". Cutting cardboard is not all that different in generating frictional heat than power-sharpening on a very dull high-grit belt using lots of pressure = the BEST way to generate the maximum amount of frictional energy. Now, there is no way that my blade travels through the cardboard at 3000 fpm (HF 1x30) but I also do not take long breaks between cuts like I do when checking the apex of a blade being sharpened - sharpening, i check the apex after every pass, giving the edge a chance to cool, whereas I cut the cardboard until the job is done = less cooling time. The difference in blade temperature between the sharpening vs the cutting does not require any kind of thermometer, it is obvious. Also the heat in the cardboard cutting extends back from the apex into the primary bevel since the entire blade is bring rubbed vs just the apex when sharpening - in the latter case, the apex can better rely on the rest of the blade to act as a heat-sink. *shrug*
 
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chiral.grolim said:
http://manufacturingscience.asmedigitalcollection.asme.org/article.aspx?articleid=1447963
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392002000200016
http://wumrc.engin.umich.edu/wp-con...ocouple_fixation_method_for_grinding_temp.pdf

Above are a few publications regarding grind-zone temps in work-pieces, all of which test dry-grinding and show a MAXIMUM temperature to be 500'C. It is noteable that the papers also mention the following:




The primary reason for using these liquids at all is their lubricity (reducing friction) and to wash away swarf that can clog the abrasive and cause irregular grinding.

When you see "red", what is it that is becoming red? The edge of the knife, or the abrasive itself, or the swarf on the abrasive? Those are 3 different things. Similarly, when there is smoke, what is smoking? I power sharpen, and not even my lawn-mower blades smoke BUT I certainly throw sparks and a clogged belt can start to burn - that is NOT the edge burning, it is the extraneous material.

Primary reason that "new blades" need to be sharpened again soon after use = initial apex was ground too thin or has a burr, or was not fully sharpened in the first place. BIG difference between a properly sharpened apex and one that is just "sharp enough" like we see from most production companies. "Burned" edges remains a theory. Not that you CANNOT burn an edge, but there is no reason to suspect it to be common. Hand-sharpening, the sharpener is usually more meticulous about getting the "perfect" edge.

When i cut cardboard, my knife edge easily gets hotter (and stays hot longer) than when i power-sharpen, and I am by no means an "experienced mill worker". Cutting cardboard is not all that different in generating frictional heat than power-sharpening on a very dull high-grit belt using lots of pressure = the BEST way to generate the maximum amount of frictional energy. Now, there is no way that my blade travels through the cardboard at 3000 fpm (HF 1x30) but I also do not take long breaks between cuts like I do when checking the apex of a blade being sharpened - sharpening, i check the apex after every pass, giving the edge a chance to cool, whereas I cut the cardboard until the job is done = less cooling time. The difference in blade temperature between the sharpening vs the cutting does not require any kind of thermometer, it is obvious. Also the heat in the cardboard cutting extends back from the apex into the primary bevel since the entire blade is bring rubbed vs just the apex when sharpening - in the latter case, the apex can better rely on the rest of the blade to act as a heat-sink. *shrug*
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Then I suppose it's not as common as I thought. It was fairly common with stainless products that my family's business manufactured but it didn't matter on a stainless steel medical cabinet going on a freighter or the underside of a steam table. The guy running the belt or stone just got in a hurry and pushed it, discoloring the metal slightly. I thought that perhaps the same thing may happen with a mass produced knife blade. As you say, it's a moot point with maxamet anyway.
 
Jim, Your K294 Phil Wilson review says 1800 cuts on the rope but the MT-24 made 1940 cuts? This surprises me. I have the brother to your trailing point Bow River also in K294(I traded my k390 for this K294) and I can't imagine a production blade beating it but I guess the numbers don't lie. I thought it would be up there with the 10v seeing it has similar composition. Any comments?


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martinsanders said:
Jim, Your K294 Phil Wilson review says 1800 cuts on the rope but the MT-24 made 1940 cuts? This surprises me. I have the brother to your trailing point Bow River also in K294(I traded my k390 for this K294) and I can't imagine a production blade beating it but I guess the numbers don't lie. I thought it would be up there with the 10v seeing it has similar composition. Any comments?


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Click to expand...

Well the K294 blade didn't have the same edge geometry etc as the knives in the list when I tested it back then.

So different testing conditions, that's why it's not in the list.
 
Would you be interested in a K294 trailing point PW with the same geometry as the top contenders. It has been sharpened one time only. I can measure again but I believe it was less than .008 behind the edge. Since 10v is the top spot I just wondered if with the edge geometry of this blade and the steel where it fall and see what manufacturer of A11 steel is better. I would also like to contribute to the on going effort monetarily. Thank you again Jim for all you do.


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