You got your Ceramic Mule. How you gonna sharpen it?

[CasperFatone]

The 1000 grit belt I used is a Silicon Carbide belt from Red Label Abrasives. It came as part of a sharpening belt set that they sell on Amazon. For $30 you get six belts (two of each 600, 800, and 1000). I’ve had them for years and honestly haven’t used them much because I tend to do my initial grind with a 220 then switch to my Edge Pro.

[FullScaler]

The 1000 grit belt I used is a Silicon Carbide belt from Red Label Abrasives. It came as part of a sharpening belt set that they sell on Amazon. For $30 you get six belts (two of each 600, 800, and 1000). I’ve had them for years and honestly haven’t used them much because I tend to do my initial grind with a 220 then switch to my Edge Pro.

Thanks,

Sic is about 2300+ vickers.
The best conversion chart I can find puts 80 HRC at about 1865 vickers.
Chromium carbides are about 65/70 HRC, molybdenum and tungsten carbides are about 75 HRC, and vanadium carbides are 80/85 HRC.

In another thread you mentioned your carbide cutters wouldn't scratch the HIC. What type of carbide cutter are you using?

Since HIC cannot be conventionally tested to Rockwell hardness I am trying to guesstimate it's hardness comparable to known vickers hardness materials that can either scratch, or not scratch it.

depending on the type of carbide cutter you are using, this info would give me a guess of between 70ish HRC, (1100 vickers) at the low end and 85+ hrc (80 HRC = 1865 HV) potentially. But under 2300 HV. (SiC hardness)

Edit to add ( Just for info, Martensite is 1000 HV, CBN is between 2800 and 4200 HV and Diamond is at 10,000HV)

[sal]

Hi CasperFatone,

Great info. Thanx much.

sal

[captnvegtble]

The 1000 grit belt I used is a Silicon Carbide belt from Red Label Abrasives. It came as part of a sharpening belt set that they sell on Amazon. For $30 you get six belts (two of each 600, 800, and 1000). I’ve had them for years and honestly haven’t used them much because I tend to do my initial grind with a 220 then switch to my Edge Pro.

This is really helpful. I only have aluminum oxide sanding belts that go from 800 grit to 1500 grit. I was going to hand sharpen my mule on some DMT benchstones, but given what I'm hearing I think maybe I'll try some diamond stropping paste on a 1x30 belt sander and see if that works instead of spending hours hand sharpening.

[CasperFatone]

The 1000 grit belt I used is a Silicon Carbide belt from Red Label Abrasives. It came as part of a sharpening belt set that they sell on Amazon. For $30 you get six belts (two of each 600, 800, and 1000). I’ve had them for years and honestly haven’t used them much because I tend to do my initial grind with a 220 then switch to my Edge Pro.

Thanks,

Sic is about 2300+ vickers.
The best conversion chart I can find puts 80 HRC at about 1865 vickers.
Chromium carbides are about 65/70 HRC, molybdenum and tungsten carbides are about 75 HRC, and vanadium carbides are 80/85 HRC.

In another thread you mentioned your carbide cutters wouldn't scratch the HIC. What type of carbide cutter are you using?

Since HIC cannot be conventionally tested to Rockwell hardness I am trying to guesstimate it's hardness comparable to known vickers hardness materials that can either scratch, or not scratch it.

depending on the type of carbide cutter you are using, this info would give me a guess of between 70ish HRC, (1100 vickers) at the low end and 85+ hrc (80 HRC = 1865 HV) potentially. But under 2300 HV. (SiC hardness)

Edit to add ( Just for info, Martensite is 1000 HV, CBN is between 2800 and 4200 HV and Diamond is at 10,000HV)

The bit I used to scratch test was tungsten carbide

[CasperFatone]

The 1000 grit belt I used is a Silicon Carbide belt from Red Label Abrasives. It came as part of a sharpening belt set that they sell on Amazon. For $30 you get six belts (two of each 600, 800, and 1000). I’ve had them for years and honestly haven’t used them much because I tend to do my initial grind with a 220 then switch to my Edge Pro.

This is really helpful. I only have aluminum oxide sanding belts that go from 800 grit to 1500 grit. I was going to hand sharpen my mule on some DMT benchstones, but given what I'm hearing I think maybe I'll try some diamond stropping paste on a 1x30 belt sander and see if that works instead of spending hours hand sharpening.

Later today I will check, but I think I may still have some silicon carbide sharpening belts for a 1x30. I gave my 1x30 to another maker when I got my 2x72, so if I still have those belts I’m happy to send them to you :)

[FullScaler]

This is really helpful. I only have aluminum oxide sanding belts that go from 800 grit to 1500 grit. I was going to hand sharpen my mule on some DMT benchstones, but given what I'm hearing I think maybe I'll try some diamond stropping paste on a 1x30 belt sander and see if that works instead of spending hours hand sharpening.

It will be interesting to see if the Aluminum oxide belts will work. Alox is quite a bit softer than SiC and pretty close to the same hardness as the Tungsten Carbide bit that CasperFatone tried to drill HIC with.

The bit I used to scratch test was tungsten carbide

Thanks, so potentially a comparable hardness above 75 HRC. This is all just comparable guessing without a proper way to physically test the hardness somehow to give us a rough idea of what may or may not work on it.

[Bolster]

What's the story on HEAT at the edge of a ceramic knife? If I were to put a steel edge to my belt grinder (regardless of the belt being used) I'd be worrying about heat and temper. What's the story with ceramic? Any problem if the edge gets hot?

[CasperFatone]

What's the story on HEAT at the edge of a ceramic knife? If I were to put a steel edge to my belt grinder (regardless of the belt being used) I'd be worrying about heat and temper. What's the story with ceramic? Any problem if the edge gets hot?

Hopefully someone with more intimate knowledge of the material can answer this. I was running my grinder pretty slow, around 20% when working the edge with the linen belt and would probably run my misting set up if I were planning to reprofile the edge with silicon carbide. In the past year or so I’ve started to do more post heat treat grinding when I make blades and the mister has been a game changer as far as how fast I can work steel.

I would think the main concern with overheating ceramics would be the risk of causing small fractures due to heat differences right at the apex. As I’m sure you know the thinner the material the faster heat builds up, which leads to expansion, and if the material doesn’t flex it may crack.

I did grind the spine of the knife closer to 50% speed for a bit but didn’t feel any real heat build up in the blade. It did throw some sparks which surprised me a little bit, but I guess it shouldn’t lol

Once I cut the handle off of this Mule to convert it into a folder I plan to do some torture testing on the off cut. I’ll be happy to torch the crap out of it or throw it in the forge to see if it breaks or gets softer

[Barmoley]

This is really helpful. I only have aluminum oxide sanding belts that go from 800 grit to 1500 grit. I was going to hand sharpen my mule on some DMT benchstones, but given what I'm hearing I think maybe I'll try some diamond stropping paste on a 1x30 belt sander and see if that works instead of spending hours hand sharpening.

It will be interesting to see if the Aluminum oxide belts will work. Alox is quite a bit softer than SiC and pretty close to the same hardness as the Tungsten Carbide bit that CasperFatone tried to drill HIC with.

The bit I used to scratch test was tungsten carbide

Thanks, so potentially a comparable hardness above 75 HRC. This is all just comparable guessing without a proper way to physically test the hardness somehow to give us a rough idea of what may or may not work on it.

When these first came out and the material became available for knives the claim was that it is 76.6 HRC. I don't know how hard the mule is, but if we are guessing, 76-77 would not be a bad bet.

[captnvegtble]

Success!

Below are my limited observations and experience taking a first stab at sharpening this HIC Mule...

1st: Don't try to sharpen by hand
2nd: Use a belt sander with a very fine grit and hard carbides and/or diamond stropping paste
3rd: Go slow and have patience

I started by using my 1x30 mini bench top belt sander with a 800 grit aluminum oxide sanding belt. I didn't see much effect with using the sanding belt alone, so then I applied some yellow DMT diamond stropping paste to the belt and periodically re-applied to uncovered areas as I progressed (note: make sure you get paste all the way to the edges of the belt). Using the flat steel back-plate on the sander, I alternated taking slow passes (couple times per side) using very light pressure and my thumb to stabilize the blade to prevent chattering. I found this to be very effective to even and smooth out the factory grind lines (which came irregular and a bit wavy). Full disclosure... I hand sharpen ALL my blades on bench stones, so using an electric belt sander was a bit of a new experience for me, so it took me 5-10 minutes to get my technique consistent and find the right bevel angle. I also found that moving the blade ABOVE the flat back-plate, decreasing the angle of the blade, and allowing the sanding belt to slightly curve around the bevel as I made passes (much like a strop), really helped to refine the edge.

I spent about 30-40 minutes take slow, light passes (not much pressure, and not much heat build-up), and I have a pretty good working edge that I'm pleased with... but it's still not hair shaving sharp so I plan on spending another 20-30 minutes tomorrow with some more diamond stropping paste to see if I can get it hair shaving sharp. Given how long this takes with a belt sander, I wouldn't recommend anybody try and sharpen this mule by hand... you could spend all day.

[yablanowitz]

Now you tell me. Mine won't shave, but I have put a useable edge on it using nothing more than my DMT Diafolds and patience. It took a few hours, but I spent half an hour carving hardwood with no edge degradation.

[Bolster]

A question for those using belt sanders/grinders: Casper F uses the hard rubber wheel of his belt sander/grinder as his backstop. Captain Vege uses the metal platen (back plate) as his backstop. Can we discuss the advantages/disadvantages of each? The rubber wheel would be round with a little give to it, and the metal platen flat and hard, obviously. Nobody has talked about using the slack (ie, unsupported) part of the belt, which tends to appleseed the edge a bit.

And while I've got the microphone, another question: Let's say you do manage to get the ceramic hair-shaving sharp. Does it hold that edge well (ie, at least as good as a quality steel), or does it quickly fracture back down to a long-lasting (but duller) edge that it can actually hold? I guess what I'm asking is whether pursuing a fine edge on ceramic is worth the trouble, or does it quickly revert to a working edge?

And for Yab: Any twisting cuts in hardwood?

[SpyderPhreak]

I’ll echo everyone’s sentiment that these could have come sharper. Also, my pair were clearly sharpened by different people (or at very least, someone who was still learning and then had figured it out awhile later), as the edge grinds are significantly different between the two. I immediately noticed the microbevel catching light, and could see it pretty well with a 10x loupe, and it seems to be a pretty high angle.

I’ve been using 3M diamond film belts on my 1x30 for a few years now for all the high-carbide super steels (Maxamet, Rex45, 15V, etc.) with excellent results. The first thing that came to mind when I heard of this mule was using those same belts to sharpen this HIC mule with. Based on a few of the posts on this page, I expect it will work well, and will be doing so this weekend. I plan to use the slack section for a lightly convexed edge. Will report results once I get it done.

For those unfamiliar, ceramic can get extremely sharp, but you have to slowly progress through the grits in order to get a fine, smooth apex, free of micro-chipping. When you get there, it can be as sharp as a fresh medical scalpel and is quite impressive. Holds the edge pretty well too if not abused.

[captnvegtble]

Nobody has talked about using the slack (ie, unsupported) part of the belt, which tends to appleseed the edge a bit.

Yes, I used the slack part of the belt towards the end of my sharpening with good effect. Just like on a strop, I needed to lower the bevel angle a bit when using the slack part.

I’ve been using 3M diamond film belts on my 1x30 for a few years now for all the high-carbide super steels (Maxamet, Rex45, 15V, etc.) with excellent results. The first thing that came to mind when I heard of this mule was using those same belts to sharpen this HIC mule with. Based on a few of the posts on this page, I expect it will work well, and will be doing so this weekend. I plan to use the slack section for a lightly convexed edge. Will report results once I get it done.

They make diamond film belts?!? Are those different from the 3M Trizact? Seems like I should buy some since that's essentially what I was doing with diamond strop paste.

[yablanowitz]

And while I've got the microphone, another question: Let's say you do manage to get the ceramic hair-shaving sharp. Does it hold that edge well (ie, at least as good as a quality steel), or does it quickly fracture back down to a long-lasting (but duller) edge that it can actually hold? I guess what I'm asking is whether pursuing a fine edge on ceramic is worth the trouble, or does it quickly revert to a working edge?

And for Yab: Any twisting cuts in hardwood?

I am new to ceramics, so I don't know how it will hold up if I do manage to get it shaving sharp. My goal is to find out.

As for twisting cuts, if you mean digging the edge in deep then twisting the blade to break out a piece of wood, no. I personally think that is stupid, proof positive that the person doesn't know how to use a knife and shouldn't be allowed to handle sharp objects without supervision. Just my opinion.

That said, what I have been doing is carving flutes - rounded spiral patterns like the bottom piece in this old picture.



That is done with a scooping motion that does put a little lateral stress on the edge, but not much.

Edit to add: I have a hunch that the "30° per side microbevel" that people have been observing is what remains of the manufacturer's edge after Spyderco has worked on it. For those who have spent the time and put an acceptable edge on, try to picture doing that 2000 times. If Spyderco had waited until they had achieved the level of sharpness people seemed to be expecting, this Mule would have dropped in 2040. Food for thought.

[CasperFatone]

A question for those using belt sanders/grinders: Casper F uses the hard rubber wheel of his belt sander/grinder as his backstop. Captain Vege uses the metal platen (back plate) as his backstop. Can we discuss the advantages/disadvantages of each? The rubber wheel would be round with a little give to it, and the metal platen flat and hard, obviously. Nobody has talked about using the slack (ie, unsupported) part of the belt, which tends to appleseed the edge a bit.

And while I've got the microphone, another question: Let's say you do manage to get the ceramic hair-shaving sharp. Does it hold that edge well (ie, at least as good as a quality steel), or does it quickly fracture back down to a long-lasting (but duller) edge that it can actually hold? I guess what I'm asking is whether pursuing a fine edge on ceramic is worth the trouble, or does it quickly revert to a working edge?

And for Yab: Any twisting cuts in hardwood?

On the subject of contact wheel vs platen vs slack belt, I prefer the contact wheel in part because I feel it’s a little more forgiving, meaning there is less of a chance to gouge the edge due to the softer backing. It also stays cooler than a platen, although when doing edges there shouldn’t be enough heat buildup to matter. The other reason I use it is that it’s what I’m comfortable with, mostly due to it lets me see the edge I’m working on better and it’s what I’m used to. I grind near the top of the wheel so when I grind a steel edge I can watch the burr form.

As far as keeping a shaving edge, last night I feathered about a dozen sticks of walnut and maple in my shop and broke down a bunch of cardboard and it’s still shaving, but maybe not quite as well as it was before. Mine were all pretty straight cuts, no real twisting in hardwood…yet :)

[ZrowsN1s]

Haven't had a chance to do anything but look at it yet

Wasn't sure if I'd get a read with the Laser Goniometer, but looks like 16 and 14 dps if the readings accurate. I'll have a better idea when I sharpen.

I could see what looked like a micro bevel with the 10x loupe.

My sharpening plans are thus...

Take a BESS measurement of the factory edge (didn't have time this morning to test it beyond noting it won't shave arm hair).

Then run it through a leather strop progression of 5, 3.5, 2, 1, .5, .25 diamond paste. And retest the edge with the BESS tester and some arm hair.

If I can get it razor, I'll likely leave it there and use it. Seeing how long I can maintain with the strop alone.

If it doesn't shave, I plan on using the wicked edge at high grit and trying to just match the main bevel, and eliminate the microbevel. No crazy reprofile. Then take it up to 3000 grit diamond. Test edge and see what I've got.

[burlyspyder]

Ok, here's some anecdotal info on the material. Before diving into sharpening the mule, I had a go at my Rahven kitchen knife.

First, I have traditionally done all my sharpening by hand on waterstones. So take anything posted here with that in mind. Second, this material is stupid-level hard, and the entire "feel" is different than anything I have sharpened before, so definitely a bit of a learning process. In particular, my three-finger-testing felt useless - it almost never felt like it was "biting" - too smooth.

I used DMT diamond blocks. I first tried the 1200, but felt I was basically not doing anything. I backed off to 600, and it was still slow going, but I could at least feel it cutting. I stayed there for a while, trying to re-establish a new edge, then back up to the 1200. I probably spent 10 sharpening minutes on the 600, checking edge and bevel often, then took a pic. I then did the same on the 1200, for maybe 20 minutes, checking push-cut on printer paper fairly often. Once I got it to a satisfactory paper cut test, I stopped and took some pics. Then I did a light couple strops on the 1200.

Here is the pic after 600:

Here is the result after the 1200:

Then here is after the stropping:

None of these felt really sharp on a 3-finger test. I never felt or saw any burr form. Also, the 1200 diamond plate also feels WAY too smooth now. It's far smoother than the 8k diamond plate. I am not sure how much more cutting power it has left, so this could get expensive if you had to sharpen this material often, or need to work out chips (made a little one on the corner of the plate and and did get it out). I can't really quantify the plate effect, but it definitely looks a bit different. It may look like a focus issue, but it is different through the range of focus. The very corner of the plate still looks like the before, and everywhere in the middle looks like it has less "depth" in the media.
Before:

After:

Now, before I work on the mule, I took some pics:
Side1:

Side2:

It looks like one side is rolled over. I took a bunch of pics, in different places, and it definitely looks like a convex edge on one side moreso than the other.

More to come...

-burly

[burlyspyder]

My resin bonded are Venev Orions. They aren't cheap, nearly $60 each.

(1) What concerns do we have about wearing out expensive stones while sharpening this mule?

(2) Will anybody attempt to reprofile to a different edge angle? (Guessing not.)

I did not consider this with diamond, but my 1200 feels like a 12000 now, after re-profiling my factory-edged Rahven. Pretty sure I spent $47 in about 20 minutes getting a mediocre sharp edge.