Stroping Ceramic Blades - Why?

[Chief31794]

I've been using them for about three years, they get dull and drag, I strop them and they cut smooth and clean again. Don't understand the physics of it, but I get dark residue on the strop and as I said it definitely has an affect.

Chief

[TapTapTap]

Hi Doc,

My experience with the ceramic blades is the same as the Chief. I keep a small strop on my bench and after a few cuts with the blade i give it a few strokes on both sides. I am also a wood carver and use the same technique with my chisels - cut for a while and then strop. It does make a difference.

regards, TapTapTap

[Mike Craw]

It's my understanding that the chemicals in the leather build up a microscopic crust on the edge that causes the drag. Stropping removes that crust and just exposes the sharp blade again.

Mike

[DrGull]

Every Tandy video by any of their instructors contains a line like: "the ceramic blades never need sharpening, but they should be stropped."

Why?

The ceramic making up those blades is an order of magnitude harder than white jeweler's rouge. Rubbing the ceramic blade with white rouge can have no impact on the ceramic blade.

Is it just some kind of ritualistic thing?

Edited October 23, 2012 by DrGull

[DrGull]

Mike:

If that is true, then there's a point to it. Do you have any kind of reference for the "crust" theory?

[TwinOaks]

Certainly....

As we know, leather is a product of a chemical process - it is preserved from deterioration by tanning it. That process makes the leather slightly acidic on the pH scale. There are also natural oils, waxes and fats that are preserved along with the skin cells. When we drag a blade - steel, ruby, or ceramic- through leather we're necessarily also dragging it through everything else IN the leather. That's where the 'crust' comes from...though I'd lean more towards 'film'

However, I think there is another possibility as well. Several people have written that they've noticed that more recently made ceramic blades have grind marks on them. It's possible that the small grind marks are picking up the same residue and "clogging" the blade, making it cut less smoothly. Stropping (as stated above) cleans out the micro grooves.

Member "Shtoink" had some very insightful observations on stropping direction with the ceramic blades....I'll see if he'd like to post them here.

Paul Zalesak at Leatherwrangers did some pretty extensive analysis and discovered that the chemicals in leather are actually corroding metal in steel blades. So, for steel blades, the leather actually is DULLING the edge...despite being a much softer substance. That's the reason that Paul developed his blades from a special alloy.....which, is a trade secret.

[King's X]

The ceramic blade can be resharpened and with rouge it can be cleaned up and polished. I have owned 3 ceramic blades and one fell and a chip was the result. With green rouge which has a valued of 8000 grit will most likely polish your blade tip to include a ceramic blade. As Chief mentioned, you want to strop your blade if for any reason to remove any residue off the tip to allow more ease of the blade when cutting into leather.

[DrGull]

Twin Oaks:

OK, I'll buy that and keep stropping. Thanks everyone for your time.

[shtoink]

I hope that I might be able to add some worthwhile content. My experience has been mostly with ceramic blade material. I'm not trying to say that is what I mostly use, but rather that I purchased a ceramic blade specifically to experiment with chipping, sharpening, and how it can be sharpened. I also have to agree that stropping a ceramic blade does little for sharpening, but it does clean up the surface from any kind of build up that may occur. Giving the blade a nice set of polished bevels significantly helps in this area as well as reduce drag when in a cut. That's the bulk of what I will talk about below.

I'm sure that many of you who have been able to make comparisons between old and new ceramic blades can attest to this, the manufacturing process has become a bit lacking. I don't have any first hand knowledge with the older stock, however these new blades from Tandy come out of the box in rough shape. They have the equivalent finish from that of a medium grit grinding wheel. Hell, I looked at some that didn't even have the cutting edge centered. There is very little effort, if any, put towards cleaning up those rough bevels. They will cut leather and depending the quality of polish you are used to before you use one the ceramic blades raw, they may be better or worse than what was just previously in your swivel knife. Those that polish their bevels to a mirror finish and can shave with it will say that it drags heavily and those that are still working on their sharpening skills will say it cuts better. The thing is, both camps are correct and it's based on perspective.

With this new ceramic blade in my hands, I inspected it closely. I was presented with ugly machining marks from a medium to worn-course grit diamond wheel and immediately started to device a way to remedy the problem. What I wanted to find was a cheap, readily available to anyone solution. I will say that it is certainly not the best or only way, but it works and can be done without exotic tools. If you have 2000, 3000, 5000, or better grit DMT diamond honing plates, by all means use them. They are excellent, but expensive and most of use don't have them and probably never will.

With that said, here is the list of things I was able to make my ceramic blade highly polished and shaving sharp with.

800, 1000, and 2000 grit 3M wet/dry automotive sandpaper.

A pane of tempered glass scavenged from an old scanner. (any sufficiently large, very flat, water resistant surface will work)

A sharpening jig from Tandy. (I'm sure that others have made them, too. I can't recommend one enough)

Dish soap, water and plenty of patience.

Lots of elbow grease.

My first attempt to clean up the blade was completely different and chipped up the edge. I bother to mention anything else about that blunder, but it served the purpose of finding out if it could be done. I now had chips that needed fixing, which contributed to the time it took fixing my blade.

Firstly, you and most of everything around you is at risk of getting wet. Decide upon an appropriate location to do this with that in mind.

Second, you must not succumb to the urge to apply pressure in both directions of the stroke if you are using the wet/dry paper. You must only apply pressure on the pulling stoke (the stroke in which the cutting edge is NOT leading). Here's why. When the paper is wet, it absorbs a small amount of water and becomes slightly spongy. When you apply pressure on the forward stroke, it causes the paper to curl and over the cutting edge. It's very minute, but it's there. What this does to your cutting edge is actually create a very fine radius and the actual angle to the cutting edge will be far steeper than anything you want. This means that your blade will still feel dull despite all your hard work.

You need to find the proper angle of your bevel. The jig can be finicky, but be patient with it. Depending on the angle you are going for, you might want to find that angle differently, but for the sake of my example, I use a 30-60-90 drafting triangle. I was able to fiddle with the little set screws on the jig until the shaft on the jig was parallel with the edge of the triangle at 30 degrees. The good news it that once you have your angle set for one side, the set screw for the blade is all that needs to be loosened and it can be flipped over.

Start by laying out the 800 grit paper and getting it plenty wet and add a few drops of dish soap. Use the length of the paper to your advantage, just don't run the jig off the edge of the paper as the thickness of it is enough to change the angle at which the blade is getting ground. Your focus is on removing those machining marks and, if required, centering the cutting edge, so there isn't a need to try and count strokes.

You can flip your blade at this point and repeat the above on the other side, but since my blade was already centered I just kept on working the one side. Since ceramic won't form the typical wire that rolls up along the cutting edge, it doesn't really need to be flipped back and forth. This is pretty much your choice, but keep in mind that it requires messing with the set screw more often and could lead to other problems if you aren't careful.

There isn't a huge amount of material being removed, but it's a very hard material, so the process seems much slower than working with steel. It might only be about 0.005" to 0.01". Those diamond hones would speed this up, but, once again, they aren't cheap. You may or may not need to use some sort of magnifying glass to see this, but it can help in letting you know just how far you've got left to go. Once all the grinding marks are removed from the bevel, the hard part is over. You can then start moving up to the 1000 and 2000 grits. The details are pretty much the same as for the 800 grit section, but your focus is now on getting the bevel polished instead of removing material. Dish soap and water, pressure on the pull stroke, wipe off and check regularly. It helps to hold it up and look at the reflection, since it's white and difficult to see what the surface looks like directly.

Once you have worked the one side, you can flip it over and do the same on the other. That is, if you weren't flipping it over between previous grits already.

If need be, I might be able to get some pictures of the before and after, but that means I need to get another blade and find a way to get some decent shots. I will also be able to answer any questions that may arise. Just keep in mind that this is specific to ceramic blades and absolutely not the best or only way. Just a cost effective and readily available method to make your ceramic blade perform orders of magnitude better than when you first pulled it from the little plastic baggy.

I hope that this has been easy enough for those of you interested to follow and I hope that you also find it helpful and use it in good health.

[shtoink]

Every Tandy video by any of their instructors contains a line like: "the ceramic blades never need sharpening, but they should be stropped."

Why?

I think I completely missed the mark in directly answering your question with my previous post. So here is my second, less wordy try at it.

The easy answer is marketing. It's a lot fluff and misinformation. They, very much, need to be sharpened right out of the gate. I would say they need to be sharpened far less than a steel blade and they probably don't need to be stropped anywhere near as often since it would only serve the purpose of cleaning off any buildup that may stick to the blade and create drag. Once you get a ceramic blade tuned the way you want it, it'll be pretty low maintenance, barring any accidental damage from dropping or banging it against something. Hopefully this and the previous post help clear things up a bit.

[shtoink]

In an effort for completeness, I managed to get some reasonable pictures of the bevels on my ceramic blades. This wasn't, altogether, easy since I still do not have a dedicated macro lens yet. The pictures I did get, I feel, manage to capture the condition of the blade right out of the package, and I have the blade that I used to test out polishing of the ceramic blades explained above for comparison. Hopefully this clears up a few of the details with points I covered in the posts above.

In these two shots, you can clearly see how rough the condition of that bevel is. Not very pretty and will cause a good deal of drag and crud to build up on the blade. Also, depending on the blade, some of those lines can run at different angles. It just depends on what blade and who was running the equipment, I guess. As usual, these are clickable thumbnails that will open up a full sized picture.

This is the side-by-side comparison to show what the blades can look like before and after addressing the condition right out of the packaging.

The last image, I was attempting to capture the reflection of the unpolished blade on the bevel of the polished blade. It's easier to make out when you open it up to full size.

[shtoink]

I recently got a new macro lens, so I decided to try and get some better shots of the difference between these two ceramic blades. Just click the picture to open up a full size view.

[Doc Reaper]

Way too much drag for me, used a business card, water, and green compound. Still drags like a yacht on land! Will try another method. This doll out of the box tells me not to get another one!

[Doc Reaper]

Not doll, I meant dull, sorry Y'all

[mikesmith648]

I still want a swivel knife like that shtoink!!!