17 Deg. (Per Side) M4 vs. 180 Grit Sandpaper: Sandpaper Won

[Sharperthansticks]

I usually think of knife abuse as hacking at concrete, prying things (especially with the tip, as opposed to a large part of the edge), and cutting metal. I figure that the rest is more or less fair game. So, I had a little project where i needed some 180-grit sandpaper, and instead of cutting it with scissors, I figured I'd use my Spyderco Advocate (which is in M4, since that's the only way they've been sold), with my 17-degree-per-side profile on it. Let's just say that didn't work too well. I had to stop after a few strokes of the Advocate and just go use my scissors, but man, what a mess of the blade I made in that short time. I thought M4 was supposed to be super tough, and maybe it is, but that day it more than met its match. It took me a long, long time on very abrasive belts at high speed on my Work Sharp blade grinder to restore the edge. Turns out that cutting very coarse sandpaper is abuse, after all, although it occurs to me that a 20-, 22.5-, or 25-degree angle may have faired a lot better. (Maybe 3V, 4V, Maxamet, or Rex-45 would have fared better, and I own all of them, but I won't be performing that experiment again.)

 

[Currawong]

No go on, perform the same experiment on each of them, would be good to see how they all fare

 

[trevitrace]

Or tuning your edge with a high speed belt affected its performance.

 

[Sharperthansticks]

No go on, perform the same experiment on each of them, would be good to see how they all fare

Crap, I was going to, but I can't see to find them. Send me a PM. I'll give you my address so you can send me yours, and I'll keep meticulous notes on how the experiments go, after which I'll send the knives back to you.

 

[Sharperthansticks]

Or tuning your edge with a high speed belt affected its performance.

This never-ending debate again? <Slowly shakes head> These knves are tempered at hundreds of degrees or *much* higher for HOURS. Even assuming -- like some people are so eager to -- that "the micro-edge heats up to blah blah blah, ruining the temper" we're talking seconds of overheating, and maybe even less than that. That argument never held any water with me.

 

[GWashington1732]

I usually think of knife abuse as hacking at concrete, prying things (especially with the tip, as opposed to a large part of the edge), and cutting metal. I figure that the rest is more or less fair game. So, I had a little project where i needed some 180-grit sandpaper, and instead of cutting it with scissors, I figured I'd use my Spyderco Advocate (which is in M4, since that's the only way they've been sold), with my 17-degree-per-side profile on it. Let's just say that didn't work too well. I had to stop after a few strokes of the Advocate and just go use my scissors, but man, what a mess of the blade I made in that short time. I thought M4 was supposed to be super tough, and maybe it is, but that day it more than met its match. It took me a long, long time on very abrasive belts at high speed on my Work Sharp blade grinder to restore the edge. Turns out that cutting very coarse sandpaper is abuse, after all, although it occurs to me that a 20-, 22.5-, or 25-degree angle may have faired a lot better. (Maybe 3V, 4V, Maxamet, or Rex-45 would have fared better, and I own all of them, but I won't be performing that experiment again.)

Yes?
Sandpaper will wipe your edge away in about 2 seconds. Should probably refrain from doing that again.

 

[stabman]

This never-ending debate again? <Slowly shakes head> These knves are tempered at hundreds of degrees or *much* higher for HOURS. Even assuming -- like some people are so eager to -- that "the micro-edge heats up to blah blah blah, ruining the temper" we're talking seconds of overheating, and maybe even less than that. That argument never held any water with me.

You can definitely screw up the heat treat with grinders/belts.

While doing the machining course in college, we ground our own cutting bits for the lathe from pre-hardened high speed steel blanks.
It was VERY easy to overheat while doing that...and you found out when you went to cut steel on the lathe, and the tip/cutting edge went busting off (or wearing off...either way is bad).

Heat can build up really fast in small sections.
Reality doesn't care if you believe the argument or not.

(Oh yeah, we were holding the blanks with bare hands to better tell the heat...still easy to screw up in a matter of seconds)

 

[Banter 247]

Increasing the edge angle would be counter productive, although only in a negligible way.

 

[FortyTwoBlades]

Thicker edges only last longer when resisting plastic deformation. Thinner edges actually last longer in resisting abrasive wear. Also, when cutting sandpaper, always cut from the backside. It'll still blunt your edge, but not half so quickly.

The aluminum oxide and silicon carbide used as the abrasive grit in sandpapers are MANY times harder than the steel of your edge and you're basically trying to cut through a thin layer of a sharpening stone on a flexible backing. Hence why cutting the backing reduces wear--you're not plowing the edge through abrasive grains until after you've separated the material, which allows the grains to more readily pass to either side of the blade since they're no longer held in place by the backing. Do it the other way 'round and the backing is basically armored by the abrasive.

 

[Petunia D. Feeble]

I usually think of knife abuse as hacking at concrete, prying things (especially with the tip, as opposed to a large part of the edge), and cutting metal. I figure that the rest is more or less fair game. So, I had a little project where i needed some 180-grit sandpaper, and instead of cutting it with scissors, I figured I'd use my Spyderco Advocate (which is in M4, since that's the only way they've been sold), with my 17-degree-per-side profile on it. Let's just say that didn't work too well. I had to stop after a few strokes of the Advocate and just go use my scissors, but man, what a mess of the blade I made in that short time. I thought M4 was supposed to be super tough, and maybe it is, but that day it more than met its match. It took me a long, long time on very abrasive belts at high speed on my Work Sharp blade grinder to restore the edge. Turns out that cutting very coarse sandpaper is abuse, after all, although it occurs to me that a 20-, 22.5-, or 25-degree angle may have faired a lot better. (Maybe 3V, 4V, Maxamet, or Rex-45 would have fared better, and I own all of them, but I won't be performing that experiment again.)

If you could manage to only hit the paper it would do fine. The problem is the sand.

You can use sandpaper to sharpen the knife. Literally grinding steel off of the blade. You can also use stones to sharpen the knife. Would you use the knife to cut stones?

 

[Fixall]

...I needed some 180-grit sandpaper, and instead of cutting it with scissors, I figured I'd use my Spyderco Advocate...

That just made me cringe so hard. That poor Advocate! It wasn't with such a high value knife (Opinel), but I've definitely made the same mistake.

I use a scribe for "cutting" sandpaper these days and prefer that method.

 

[miso2]

Sounds like complaining that the edge becomes dull quickly when cutting into a sharpening stone.
Of course it would.

 

[Petunia D. Feeble]

Deal spotting, I know, but this is for the good of the knife community as a whole:

Thats 360 blades (counting each individual snap off segment) for $15. Please don't use a good folding knife to cut abrasives.

 

[DeadboxHero]

I use trauma shears for cutting sandpaper.

I use a lot of sandpaper, piles of it.

If cutting sandpaper was the test of tests for hardcore knife steel performance then I guess that means the pot metal my trauma shears are made out of is the ultimate blade steel.

Or it's probably just that structure is function.

If you're testing a Lamborghini in rock crawling off road competition, it's gonna suck.

Doesn't mean Lambos suck.

Context is everything boys

 

[GWashington1732]

I use trauma shears for cutting sandpaper.

I use a lot of sandpaper, piles of it.

If cutting sandpaper was the test of tests for hardcore knife steel performance then I guess that means the pot metal my trauma shears are made out of is the ultimate blade steel.

Or it's probably just structure is function.

If your testing a Lamborghini in rock crawling off road competition, it's gonna suck.

Doesn't mean Lambos suck.

Context is everything boys

The scissors from a suture kit work for me. They can't cut anything else, but they do good on sandpaper.

 

[craytab]

I usually think of knife abuse as hacking at concrete, prying things (especially with the tip, as opposed to a large part of the edge), and cutting metal. I figure that the rest is more or less fair game. So, I had a little project where i needed some 180-grit sandpaper, and instead of cutting it with scissors, I figured I'd use my Spyderco Advocate (which is in M4, since that's the only way they've been sold), with my 17-degree-per-side profile on it. Let's just say that didn't work too well. I had to stop after a few strokes of the Advocate and just go use my scissors, but man, what a mess of the blade I made in that short time. I thought M4 was supposed to be super tough, and maybe it is, but that day it more than met its match. It took me a long, long time on very abrasive belts at high speed on my Work Sharp blade grinder to restore the edge. Turns out that cutting very coarse sandpaper is abuse, after all, although it occurs to me that a 20-, 22.5-, or 25-degree angle may have faired a lot better. (Maybe 3V, 4V, Maxamet, or Rex-45 would have fared better, and I own all of them, but I won't be performing that experiment again.)

This is just silly. You consider using a knife on concrete abuse but not on sandpaper? Glad you learned a lesson here.

And yeah, using a work sharp for a long, long time at high speed can burn the edge.

 

[dirc]

Thicker edges only last longer when resisting plastic deformation. Thinner edges actually last longer in resisting abrasive wear. Also, when cutting sandpaper, always cut from the backside. It'll still blunt your edge, but not half so quickly.

The aluminum oxide and silicon carbide used as the abrasive grit in sandpapers are MANY times harder than the steel of your edge and you're basically trying to cut through a thin layer of a sharpening stone on a flexible backing. Hence why cutting the backing reduces wear--you're not plowing the edge through abrasive grains until after you've separated the material, which allows the grains to more readily pass to either side of the blade since they're no longer held in place by the backing. Do it the other way 'round and the backing is basically armored by the abrasive.

Very good point, I think it really is the aluminum oxide (https://en.wikipedia.org/wiki/Corundum) with a mohs hardness of 9.0 that kills it.
If the m4 was hardened past 60 (which should be the case for any decent m4), and the sandpaper only had silica (mohs 6.0), it should have been fine, right?

 

[Natlek]

I usually think of knife abuse as hacking at concrete, prying things (especially with the tip, as opposed to a large part of the edge), and cutting metal. I figure that the rest is more or less fair game. So, I had a little project where i needed some 180-grit sandpaper, and instead of cutting it with scissors, I figured I'd use my Spyderco Advocate (which is in M4, since that's the only way they've been sold), with my 17-degree-per-side profile on it. Let's just say that didn't work too well. I had to stop after a few strokes of the Advocate and just go use my scissors, but man, what a mess of the blade I made in that short time. I thought M4 was supposed to be super tough, and maybe it is, but that day it more than met its match. It took me a long, long time on very abrasive belts at high speed on my Work Sharp blade grinder to restore the edge. Turns out that cutting very coarse sandpaper is abuse, after all, although it occurs to me that a 20-, 22.5-, or 25-degree angle may have faired a lot better. (Maybe 3V, 4V, Maxamet, or Rex-45 would have fared better, and I own all of them, but I won't be performing that experiment again.)

I cut 40 grit AO and Zirconia sandpaper for my 3 disk grinder almost every few days with one of my M35 HSS steel blade /I think it is 67 hrc/ .I don t remember sharpening angle but sandpaper make very very little damage on edge ... But I cut from back side of sandpaper if that matter
Small one on picture . . . .

 

[Getting older]

The back edge of a hacksaw blade,or the toothy side,lay it on the sandpaper and pull against it.Or fold the paper and tear along the fold.No knife that's your pride and joy to used for that.

 

[Natlek]

. It took me a long, long time on very abrasive belts at high speed on my Work Sharp blade grinder to restore the edge. .)

You doing something VERY wrong if you need long time on very abrasive belts at high speed Work Sharp blade grinder to restore the edge... Give that to me and I will restore your edge with 800 grit DMT diamond stone till you drink one beer
It is MYTH that Super duper steel are hard to sharpen or hard to grind with belts ...Ceramic belts don t care what is under them my friend.....they will grind BEVEL in fraction of time not half mm edge
PS . What is your definition for very abrasive belts what kind of belts you use on that sharpener ?