Tungsten carbide sharpening ?

barkingspider2007 said:
Posted a video sharpening the Sandrin Torino

The video has microscope images..
The video is indexed in the description.

Let me know what you think. :cool:
:thumbsup:
Click to expand...

You do of course realize that we can't tell much from a video. We can of course see that you removed ink or metal from the bevel across its entire width, but that alone doesn't necessarily indicate that the knife was apexed. You need to examine the actual apex with a loupe or microscope as well. And I think it might behoove you to work on fine tuning your microscope lighting. Did you try another slice test?
 
barkingspider2007 said:
Posted a video sharpening the Sandrin Torino

The video has microscope images..
The video is indexed in the description.

Let me know what you think. :cool:
:thumbsup:
Click to expand...
Thanks for sharing, it's always more engaging when people share videos of stuff. It's 2022 and we should have more videos now that everybody has a smartphone with a camera. Good job.
 
eKretz said:
You do of course realize that we can't tell much from a video. We can of course see that you removed ink or metal from the bevel across its entire width, but that alone doesn't necessarily indicate that the knife was apexed. You need to examine the actual apex with a loupe or microscope as well. And I think it might behoove you to work on fine tuning your microscope lighting. Did you try another slice test?
Click to expand...
The microscope I have is a USB with limited depth of field. If a proper laboratory microscope were used the pictures would be better.
- I am beginning to believe that Sandrin tungsten carbide edges behave much like ceramic.
- Alex from YouTube channel Outdoors55 has a good video on sharpening ceramic

What worked is at
9:00 to 12: GREAT VIDEO.. WORTH WATCHING : )

========================

I think good results might be had using:
- Bench Grinder at speed at 2,000 or lower
- Paper wheel loaded with 3 micron diamond paste

So..
Harbor Freight Bench Grinder $130.00

Paper Wheel: $40 Diamond Paste $30

$200 and it may work..

Or Mabe I should go back to enjoying M4, K390, Maxamet, Rex45

Who am I kidding... Just need to buy the equipment and give it a try. : )
First world problems
 
20% binder is a lot and the carbide grains are pretty small. The carbide used for "normal" end mills for metal cutting is generally 6-10% binder and 1-3 micron carbide grains. The carbide in my favorite end mills is sub .6 micron and 12% binder, which has double the transverse rupture strength compared to "normal" carbide. As for being able to get that knife shaving sharp I would expect it to. I certainly have seen carbide tools made for aluminum and especially plastics that are shaving sharp. I found that when sharpening ceramic edge trailing passes are a must, you need to figure out where to stop with your stones as there comes a point where the finer stones will increase edge chipping, and finish with diamond loaded strops. The reason for the shift from stone to strop is how firm the "bond" is and point loading on the blade. The softer "bond" will not point load like the harder stone causing the chipping in the apex. You really need a decent microscope to figure out what is going on so you know what to do.

Funny thing is I just finished up a grinder set up yesterday to grind carbide scraper blades. I then spent about an hour grinding what I have with a 5" disk Matrix 650. As long as I kept it wet it ground quite fast, considering what it is.
 
All microscopes have a pretty limited depth of field at high magnifications. You can get a higher depth of field (and longer working distance) with a smaller aperture lens but you lose resolution. Lighting is critically important. Angle of the light and the item being observed also.

And I'm absolutely going to concur with Diemaker - you ought to be able to get a very very keen edge on submicron carbide. The strop may be helpful to you, really gotta watch that pressure. I've also successfully sharpened a ceramic blade without power tools several times. Diamond plates and a leather strop with diamond paste did the trick just fine. The use of light pressure is very important on ceramic also. Powered sharpening pretty much requires the use of light pressure, as if you push the blade into the wheel too hard you'll chew it right up.

And I do hope that you're planning on lapping the scraper blades? Unless you and I are talking about different kinds of scraper.
 
Last edited:
Diemaker said:
20% binder is a lot and the carbide grains are pretty small. The carbide used for "normal" end mills for metal cutting is generally 6-10% binder and 1-3 micron carbide grains. The carbide in my favorite end mills is sub .6 micron and 12% binder, which has double the transverse rupture strength compared to "normal" carbide. As for being able to get that knife shaving sharp I would expect it to. I certainly have seen carbide tools made for aluminum and especially plastics that are shaving sharp. I found that when sharpening ceramic edge trailing passes are a must, you need to figure out where to stop with your stones as there comes a point where the finer stones will increase edge chipping, and finish with diamond loaded strops. The reason for the shift from stone to strop is how firm the "bond" is and point loading on the blade. The softer "bond" will not point load like the harder stone causing the chipping in the apex. You really need a decent microscope to figure out what is going on so you know what to do.

Funny thing is I just finished up a grinder set up yesterday to grind carbide scraper blades. I then spent about an hour grinding what I have with a 5" disk Matrix 650. As long as I kept it wet it ground quite fast, considering what it is.
Click to expand...
Diemaker,
Excellent answer \ description of how carbide behaves.
Q) Will carbide form a detectable burr? or do you treat it like ceramic...
Q) With carbide edge use trailing strokes Y/N
Q) I never continued to the point of getting a burr (Just stopped when the edge felt right) Will carbide form a burr?
Q) When I switch to using a bench grinder is a paper wheel best or a leather one? or other?

Finally should put the knife away until the grinder is setup?

I have learned a lot from the information on the forum.
Thank you very much.
: )
 
eKretz - I will be scraping 2 cast iron adapter plates that go between the 2 rotary axes and the machine tables on a new cnc mill I got recently. The hole patterns on the rotaries and the table, no t-slots, don't line up so an adapter plate is a must. I have scraped aluminum before with files but this is the first for carbide and cast iron. The scrapers are Sandvicks as well as the blades, both 20mm and 30mm sizes with 40mm and 90mm radiuses. How polished should the edges be? The 650 at 2500ish rpm leaves a pretty smooth finish but I can go down to 1.5 micron in many steps of resin bond diamond cup wheels.

barkingspider - I doubt your carbide blade is as fragile and prone to chipping as even white Kyocera ceramic, probably closer to a SS Maxamet in a S90V flavor, if such existed. Don't get in a hurry, back and forth strokes with the coarser stones, edge trailing as you get a fairly fine apex, you will know when the microchips start getting worse instead of better. I don't know if you will need to go to a strop like you do with ceramic. I would say use your Matrix stones from the 80 to the 4000 as needed, making sure you remove the scratches from the last grit, and go from there. I like to raise my angle .2 degrees or so for the last 2 stones to make sure I am truly reaching the apex with them instead of just polishing the bevel. If you do this just use very light pressure, and do check for microchipping under the microscope as you can't do this with stones on ceramic, but strops work great. I would try finishing with bare leather just in case there is any foil burr since fine diamonds like to leave them, and 20% binder is a lot which may leave a burr.

I really don't think you will get a burr. This is where a good microscope is so nice to have as you can see what is happening when you can't quite feel it.

I think you can get a finer edge with your manual sharpener than powered so I wouldn't be thinking of using anything other than what you have. The only thing I might add is using wather carrier diamond loaded leather dry, or bass wood, as the strop to use after the stones.
 
Diemaker said:
eKretz - I will be scraping 2 cast iron adapter plates that go between the 2 rotary axes and the machine tables on a new cnc mill I got recently. The hole patterns on the rotaries and the table, no t-slots, don't line up so an adapter plate is a must. I have scraped aluminum before with files but this is the first for carbide and cast iron. The scrapers are Sandvicks as well as the blades, both 20mm and 30mm sizes with 40mm and 90mm radiuses. How polished should the edges be? The 650 at 2500ish rpm leaves a pretty smooth finish but I can go down to 1.5 micron in many steps of resin bond diamond cup wheels.

barkingspider - I doubt your carbide blade is as fragile and prone to chipping as even white Kyocera ceramic, probably closer to a SS Maxamet in a S90V flavor, if such existed. Don't get in a hurry, back and forth strokes with the coarser stones, edge trailing as you get a fairly fine apex, you will know when the microchips start getting worse instead of better. I don't know if you will need to go to a strop like you do with ceramic. I would say use your Matrix stones from the 80 to the 4000 as needed, making sure you remove the scratches from the last grit, and go from there. I like to raise my angle .2 degrees or so for the last 2 stones to make sure I am truly reaching the apex with them instead of just polishing the bevel. If you do this just use very light pressure, and do check for microchipping under the microscope as you can't do this with stones on ceramic, but strops work great. I would try finishing with bare leather just in case there is any foil burr since fine diamonds like to leave them, and 20% binder is a lot which may leave a burr.

I really don't think you will get a burr. This is where a good microscope is so nice to have as you can see what is happening when you can't quite feel it.

I think you can get a finer edge with your manual sharpener than powered so I wouldn't be thinking of using anything other than what you have. The only thing I might add is using wather carrier diamond loaded leather dry, or bass wood, as the strop to use after the stones.
Click to expand...
Hey,
Thanks Soooo Much!
I think this will work. 🥳 🙌 👍
🤞
 
Diemaker said:
eKretz - I will be scraping 2 cast iron adapter plates that go between the 2 rotary axes and the machine tables on a new cnc mill I got recently. The hole patterns on the rotaries and the table, no t-slots, don't line up so an adapter plate is a must. I have scraped aluminum before with files but this is the first for carbide and cast iron. The scrapers are Sandvicks as well as the blades, both 20mm and 30mm sizes with 40mm and 90mm radiuses. How polished should the edges be? The 650 at 2500ish rpm leaves a pretty smooth finish but I can go down to 1.5 micron in many steps of resin bond diamond cup wheels.
Click to expand...

Then yes, we are talking about the same kind of scraping. Sandvik makes good quality scraper blades, you should be happy with the performance of those. The smoother the edge you can get on the scrapers, the nicer and longer they will cut. If you run them too coarse you'll find that they dull quickly and you get a lot of scratches instead of smooth shiny scraping marks. I like to use a slow, powered aluminum lap with 9μ diamond paste rolled into the lap with a bearing race. This cuts finer than the 9μ might suggest and produces a mirror finish to the naked eye. A 1200ish grit grinding wheel might do okay also, but you need to be careful at the finer grits with grinding wheels and no coolant - the heat can cause problems with micro cracking/fracturing which will make the edge fail rapidly. Fine grit wheels at high speed get the carbide hot fast. Sharpen frequently as soon as you notice a decrease in performance. If you follow that advice, sharpening will be quick and easy also. You don't need many steps, a simple coarse grit for shaping and the finer one for finishing will do.

What angle are you sharpening at? Generally for cast iron I like a -5° angle to the straight part of the blade (so the included angle to the side would measure 95°). Sharpen one side, flip, sharpen the other - this leaves a line where they meet in the middle. You might also find this somewhat helpful if you're relatively new to scraping:

JycI18g.jpg
 
Last edited:
Thank you for the info. I have been absorbing any info on scraping I have come across over the years but rarely have needed to do it. I am set up to do 0 or 5 degrees on my grinder and have ground my blades at -5. Being resin bond wheels I always keep them wet so no worries about harming the carbide and I will play with finer grits for a better polish.
 
That level of magnification is getting closer but the main question it leaves for me is, are the white spots and unevenness of the apex showing residual damage from sharpening or is it the photo?

You can never have enough magnification or good enough focus, at least with any microscopes I have used. I will post a photo of my microscope set up when I have more time later.
 
Concur with DM. I can't make out the detail at the edge either. That could be partially down to missing focus, it could be that the microscope can't resolve the detail very well. Resolution is important. I use a metallurgical microscope, we've discussed microscopes a little in this thread:

Post your coolest microscope images

So I noticed in the threads where microscope images are posted there always seem to be a lot of appreciative comments, thought it would be nice to have a thread for those who appreciate seeing edge micrographs. I'll start things off with this image of a Feather AC Pro straight razor blade I took...
www.bladeforums.com www.bladeforums.com
 
Diemaker said:
That level of magnification is getting closer but the main question it leaves for me is, are the white spots and unevenness of the apex showing residual damage from sharpening or is it the photo?

You can never have enough magnification or good enough focus, at least with any microscopes I have used. I will post a photo of my microscope set up when I have more time later.
Click to expand...
The focus is off a little. I have moved the microscope off the work bench and now have it mounted to the wall behind my work table. (usb microscope on a camera mount arm, attachd to the wall)
The pictures should be clearer now that the vibration from the table has been eliminated)
 
Another question is: what is the resolution of the camera on your microscope? If it's too low you won't get that great of an image either. If you are looking at a blade with submicron carbide particles to see if any are chunked out of the edge, it will obviously be difficult to see those if your microscope (and camera, in combination) can't resolve them.
 
Last edited:
You must log in or register to reply here.
Back
Top