Tungsten carbide sharpening ?

Edge trailing might work, but it's definitely not recommended. Tungsten carbide is a sintered mix with usually a cobalt binder. Because of this it cuts fairly easily with diamond abrasive - when sharpening at coarser grits the abrasive mainly pulls tungsten carbide out of the matrix leaving a ragged edge that will be difficult to remedy with finer grit abrasives. The problem using edge trailing is that you stand the chance of pulling an excess of TC particles out of the sintered matrix, as it holds much better with the particles in compression than tension. Once you get to finer grits you might and might not find it such a problem. I sharpen tungsten carbide all the time on a tool and cutter grinder - I never grind with the wheel rotating away from the edge or it will chip and fracture the edge, and that's almost always at a much wider included angle.
 
Edge leading strokes would cut most lapping film. I only use edge trailing strokes.

Video link to what I use to sharpen my Sandrin Torino.. (my channel)


I am going to follow up with an actual sharpening demonstration.
 
eKretz said:
Edge trailing might work, but it's definitely not recommended. Tungsten carbide is a sintered mix with usually a cobalt binder. Because of this it cuts fairly easily with diamond abrasive - when sharpening at coarser grits the abrasive mainly pulls tungsten carbide out of the matrix leaving a ragged edge that will be difficult to remedy with finer grit abrasives. The problem using edge trailing is that you stand the chance of pulling an excess of TC particles out of the sintered matrix, as it holds much better with the particles in compression than tension. Once you get to finer grits you might and might not find it such a problem. I sharpen tungsten carbide all the time on a tool and cutter grinder - I never grind with the wheel rotating away from the edge or it will chip and fracture the edge, and that's almost always at a much wider included angle.
Click to expand...
I sharpen the Sandrin Torino with a TSPROF clamp style sharpener.
(very different from using a grinder)

1. The results using 2,300 and 4,000 grit resin bonded diamond stones followed by 3 steps of lapping film were very good. (not perfect)

- Edge leading and trailing strokes with the diamond resin stones
- Edge trailing only with the lapping film
The cutting performance is not as smooth as I would like.

I am going to have a look under a microscope to figure out what is going on.

=====================
Going to try:

1. Just lapping film edge trailing only 6 steps 30 micron to .5 micron
2. Just lapping film edge leading (very light touch) might not end well for the film.
3. edge leading only using Diamond stones (Edge Pro Matrix stones)

The Sandrin Torino knife I purchased was used.
The edge needed work.

If any one has the answers I'd love to hear from you. : )
=======
UPDATE:
THIS IS WHAT THE EDGE LOOKS LIKE UNDER MAGNIFICATION
Human hair on the left edge.
Feels very sharp.. Cuts ok, not fantastic.

I am looking for "WOW"
not yet there.

If any one has the answers I'd love to hear from you. : )

Under Microscope Sandrin Torino.jpgTIP.jpg
 
Last edited:
OK.. Third time might be a charm...

Used 9Micron, 6Micron and 3Micron lapping film
- Oil for lubrication
- Edge leading and trailing strokes for the 9 and 6 micron film
- Edge trailing for the 3 micron film
- TSPROF Blitz fixed clamp sharpener
- Edge Pro blanks
- StatesLLC.com Lapping Film (same as KME films, better than Edge Pro branded film)

The outcome was surprising.

1. The film did not get cut
2. Material removal was substantial \ very fine particles floating in the oil.
3. The edge is much sharper than my first 2 attempts.
4. 28 minutes to get and edge
5. I believe the knife is "Factory" sharp or better
6. Stopping at 3micron might be the best way

Having purchased the blade used, it may have had more edge damage than was evident.

I hope the edge retention is as good as others have reported.
The knife has been frustrating and fun to play with at the same time.
 
In your second magnified photo I can literally see edge damage (jagged edge, looks like chunks missing) that looks just like what happens if grinding with the wheel rotating away from the edge. You likely did that with edge trailing work on the coarser grits. You may want to try a lot more work on the finer grit stuff and also to keep it edge leading. You shouldn't have a problem tearing diamond lapping film with edge leading strokes as long as you don't orient the blade improperly.

Also, as you are discovering, there's a reason that powered grinders are almost universally used for grinding tungsten carbide - they are a massive timesaver. The mechanics of the sharpening process are not a whole lot different with TC, whether you use a grinder or sharpen by hand. Tungsten carbide is very different from steel, for which those processes are quite a bit more different.

You should not *need* to strop, though it might make it easier for you to get that last bit out of the edge. Tungsten carbide will not form a burr. Also remember to be very gentle on the pressure, especially anywhere that contact area is low, like at the tip of the blade. Most TC will easily chip/crumble or shatter with too much pressure on too small an area - much much easier than most steel. How easily will be dependent on binder to TC ratio. I'm guessing there's a lot more cobalt in those blades than in most TCs, so they may be a little tougher, but still aren't going to be great.
 
Last edited:
Ekretz,

I was trying to error on the side of not overdoing the sharpening.
The knife is 20% cobalt and it is easy to remove material.
It could be that I am stopping short of getting it sharp.

============
Todd Simpson - (science of sharp) sent me an email on the topic:

Dan,

It will be the same as sharpening ceramic, except that only diamond or CBN will work.
It will not form a burr, so you must avoid coarse grits and also no reason to use edge leading strokes.

I do not believe it makes sense to create a keen “shaving” edge on these materials, they get their cutting ability from the broken apex. But if you want to achieve that, you will need diamond strops.

I have no experience with these blades, but I expect resin-bonded diamond will work well.

=============
According to Todd:
1. It will not form a burr
2. Avoid coarse grits
3. The cutting ability comes from the broken apex

My use of the knife bears this out the material feels like it catches on paper when cutting.
The "shaving sharp" edge has thus far been elusive. (it will shave but not at the level of other steels)

I want to use the knife as an EDC box cutter / open the mail utility blade.

A micro serrated edge might be what is needed.
I need a better microscope to see the edge clearly.

The jury is out on the topic for now.
The answers lie in trial and error

or
Having Knife steel nerds \ Todd Simpson \ Sandrin
Take a deep dive into showing how to best sharpen the steel with pictures to back it up.
None of the experts have actually sharpened the Sandrin knives.
WValtakis said:
Yup, diamonds work just fine...I use DMT for my touch-ups on my Torino.
Click to expand...
 
I never really expected the Sandrin to take and hold a razor edge like a fine-grained low alloy steel. I touch mine up on a fine DMT with light pressure to where it will shave, but just...this edge glides through cardboard and lasts a LONG time for me.
 
Same here.. What grit DMT stone?
Do you use multiple steps?
I may be taking the sharpening too far. (3micron last step)
My expectations of the absolute sharpness might be too high.

Thanks for the reply. : )
 
barkingspider2007 said:
Same here.. What grit DMT stone?
Do you use multiple steps?
I may be taking the sharpening too far. (3micron last step)
My expectations of the absolute sharpness might be too high.

Thanks for the reply. : )
Click to expand...
DMT labels the green extra fine at 9 micron, that's the lowest I ever use👍
 
barkingspider2007 said:
Ekretz,

I was trying to error on the side of not overdoing the sharpening.
The knife is 20% cobalt and it is easy to remove material.
It could be that I am stopping short of getting it sharp.

============
Todd Simpson - (science of sharp) sent me an email on the topic:

Dan,

It will be the same as sharpening ceramic, except that only diamond or CBN will work.
It will not form a burr, so you must avoid coarse grits and also no reason to use edge leading strokes.

I do not believe it makes sense to create a keen “shaving” edge on these materials, they get their cutting ability from the broken apex. But if you want to achieve that, you will need diamond strops.

I have no experience with these blades, but I expect resin-bonded diamond will work well.

=============
According to Todd:
1. It will not form a burr
2. Avoid coarse grits
3. The cutting ability comes from the broken apex

My use of the knife bears this out the material feels like it catches on paper when cutting.
The "shaving sharp" edge has thus far been elusive. (it will shave but not at the level of other steels)

I want to use the knife as an EDC box cutter / open the mail utility blade.

A micro serrated edge might be what is needed.
I need a better microscope to see the edge clearly.

The jury is out on the topic for now.
The answers lie in trial and error

or
Having Knife steel nerds \ Todd Simpson \ Sandrin
Take a deep dive into showing how to best sharpen the steel with pictures to back it up.
None of the experts have actually sharpened the Sandrin knives.
Click to expand...

I've had a few email conversations with Todd myself, he's a pretty smart guy. It's good to see that we agree on his points 1 and 2. Point 3 I will not totally agree on, but with conditions. The cutting ability is going to be dependent on the grain size of the tungsten carbide particles and the percentage of binder that is present. A coarse grade of carbide will result in a comparatively ragged edge. A submicron grade can easily get shaving sharp. It might be worth asking the knife maker what size carbide grains are in the knife. It certainly appeared to cut paper smoothly and cleanly in the video from them.
 
Ekertz,

I put a 600 grit edge on my knife last night.
Every other knife in the collection is a better slicer of paper.

The edge tends to snag a little bit.
Cuts cardboard better than a brand new utility razor blade.
Takes 3x the force of my PM2 in K390.
Still cuts very well if handed to a person who has no frame of reference.

The patent reports a preferred binder content of 20-25% cobalt, and a carbide size of

0.6-0.8 microns.

Larrin Thomas has an article on the topic:
knifesteelnerds.com

Sandrin Carbide - What is it? - Knife Steel Nerds

The cemented carbide materials used in Sandrin's knives is unique and very different from steel. What are the properties of carbide and how does it compare?
knifesteelnerds.com knifesteelnerds.com

The factory edge might be obtained by "cutting" the carbide with high speed grinding.
Using conventional sharpening by hand might be taking the edges off the carbide.

A high power microscope look at both factory edge and sharpened edge might shed some light on the topic.

Thank you for replying.

Dan
 
barkingspider2007 said:
Ekertz,

I put a 600 grit edge on my knife last night.
Every other knife in the collection is a better slicer of paper.

The edge tends to snag a little bit.
Cuts cardboard better than a brand new utility razor blade.
Takes 3x the force of my PM2 in K390.
Still cuts very well if handed to a person who has no frame of reference.

The patent reports a preferred binder content of 20-25% cobalt, and a carbide size of

0.6-0.8 microns.

Larrin Thomas has an article on the topic:
knifesteelnerds.com

Sandrin Carbide - What is it? - Knife Steel Nerds

The cemented carbide materials used in Sandrin's knives is unique and very different from steel. What are the properties of carbide and how does it compare?
knifesteelnerds.com knifesteelnerds.com

The factory edge might be obtained by "cutting" the carbide with high speed grinding.
Using conventional sharpening by hand might be taking the edges off the carbide.

A high power microscope look at both factory edge and sharpened edge might shed some light on the topic.

Thank you for replying.

Dan
Click to expand...

I think with a little more work you might surprise yourself. It is possible to get the same edge by hand but it will take a significant investment of time. Larrin's article demonstrates fairly well what I mentioned about the difference in edge quality related to carbide grain size. I will also stress again that you should be extremely cautious with both the use of edge trailing and the amount of pressure used on tungsten carbide.

Pethaps Todd could help you out with that microscope imaging. He volunteered to help me before with a project that he found interesting, although I didn't take him up on it.
 
Ok,

My plan is to:

Use lapping film only
9Micron,
6Micron
3Micron
1Micron
.5Micron

- Oil for lubrication
- Edge trailing super light touch
- Counting the strokes and doing both sides equally

When finished strop?
Any other ideas?
The Sandrin Tungsten carbide cuts fairly quickly.

I may be over doing it?

Thanks for your help
Dan
========

Sandrin recommends:
30Micron
9Micron,
6Micron

Lame Degree of detail \ "really show me"?
3Micron
 
Why not try edge leading as suggested? Maybe that's why you aren't getting the results you are hoping for.
 
It will be hard to tell when you're actually down to the apex without at least a decent level of magnification, so hopefully your microscope can do that. As mentioned, you won't get a burr when the blade is apexed so you need to be able to inspect it well enough visually. I would do that at every grit level. I think you will be okay edge trailing as long as you use finer grits and take it easy on the pressure. If you do damage at the coarse level using edge trailing, it will take a lot of work to get it out with the finer grits, and it's easy to miss if you don't pay attention/know what you're looking for.
 
You must log in or register to reply here.
Back
Top