Parting Tool Razor

Yes, definitely best edges as far as cleanliness will be with diamond, that much is pretty evident. That doesn't mean that a comfortable edge won't be achievable on other stones though. The carbides are awfully small, so as long as they aren't torn out creating a very ragged edge in too high of a percentage of the edge it probably won't even be noticeable in a shave. Ugly scope shots of edges that shave pretty well are not that uncommon.

As far as substrate, I think a soft substrate may do just fine. The diamond particles are so small that I think they will still be able to reach the pressures needed to take their nibbles out of the carbides. I can try it anyways, I have plenty of diamond lapping compound laying around as well from my machining and toolmaking days.

Here are a few more scope shots from further tests.

First up, bevel finished on DMT EEF (8k, 3 micron):

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I decided to try the found natural stone I sent on a passaround last year, as it's a strong cutter on slurry - the Kuro Slate I call that one. Finished on tomo slurry then straight water. It slightly convexed the apex, as slurry honing does, and to reach the apex on straight water I had to add a layer of tape:

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Edge lit shot resulting from above work:

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Here's the Suehiro Gokumyo 20k-finished bevel with the carbides sticking out. My scope's measuring software says they are about 3- 4 microns in diameter:

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That doesn't look bad. Tried a shave yet?

Yep, but I don't have a regular shaped razor yet, just a short test edge, so I can only report that it shaves fine WTG, can't really get a feel for whether the edge is super comfy ATG yet, the shape/grip is too unwieldy to try it. I'll get the blank cut out shortly and then I need to get something set up to hollow grind it. I'm going to go for at least ¼ hollow, perhaps ½ hollow. I don't want to go too far and make it too fragile.

Did one last test before starting on the blank to try some pasted strop progression.

Ring Light shot - progression went DMT EEF to .25u CBN to .1u CBN to .05u PCD. All of these shots have edge artifacts that make the edge look weird because of the ridiculous level of polish except the actual edge shot, BTW.



Raking Light shot:



Edge Lit... Very nice:



And this one demonstrates the extreme fragility of the steel - I dropped the test piece onto pretty soft linoleum and did this:

I also rehoned another SG20k edge because I did the first one after the Ozuku honing and wondered if it might have eroded the steel matrix and left the carbides sticking out more than the SG20k would from the DMT EEF. So this is DMT EEF to SG20k. As you can see, it is able to cut the carbides somewhat better near the edge but it's still cutting more around them and pulling them out. Plenty of carbides up from the apex a bit that look like they're about to fall off the bevel or loose already.

Raking Light:



Edge Lit:

How fun , this tread is. The knowledge here is amazing

What were you using for a substrate... balsa? And what is .05u PCD? PolyCrystalline Diamond? I have been thinking about trying something finer than .1u diamond. Great photography. Looks like a pretty good edge, too. Can't wait to see the finished razor.

Amazing work you are doing here!

Thanks fellas, I'm glad everyone else is having as much fun as I am!

The shots from the compound progression were edges stropped on a thin semi-stiff microfiber cloth (sort of like a very fine felt) mounted on flattened glass tile using light pressure, just enough to keep flat contact. And yup, the PCD is polycrystalline diamond - I think the brand is Buehller MetaDi IIRC. That stuff really cuts quick. Out of the three strops, it discolored the most.

I probably could have started with some 3u diamond or at least 1u if I wanted the bevel prettier, but I was mostly concerned with getting the job done at the apex, where it counts.

Most of the time when we think of diamond pastes we speak in terms of 5 laps or maybe ten laps. How many laps are you doing on this material to produce the effects we are seeing?

This was about 30 laps on each. Since I started a bit finer than I should have (and since it's HSS) I did some extras so I would be sure I didn't have to go back to the scope. Discoloration is pretty obvious because the material was new and it's white.

eKretz said:

This was about 30 laps on each. Since I started a bit finer than I should have (and since it's HSS) I did some extras so I would be sure I didn't have to go back to the scope. Discoloration is pretty obvious because the material was new and it's white.

Click to expand...

Thank you! That is exactly what I wanted to know. That is some seriously hard stuff!

That's for sure. Very hard indeed - even stones like Chosera and Shapton will hardly touch the stuff. I pity the fool who would try to set a bevel on a HSS razor or knife without diamond abrasives or a belt sander, heh. And then there's Stellite - even another step up the 'nasty' ladder.

I made the acquaintance of a fellow online who has done some testing of low angle HSS knives and his favored method of sharpening was with lapping films and CrOx stropping afterward, so I said I'd do another test edge and post the scope shots here for him to see how his way works. Here's the result - some carbide exposure and surely subsequent tear-out will occur using this method, as I used diamond up to 3 micron then switched to 3 micron and 1 micron AlOx lapping film before running about 30 laps on a CrOx loaded leather strop and then some bare leather, and the carbide exposure is already very evident.

Ring Light Shot:



Here's the raking light shot - carbides evident:



Edge Lit Shot - not too bad:

This is a fantastically interesting thread! I know working with this stuff is difficult, but thank you so much.

You're welcome, it is a bit of work doing all the prep and honing, but it's kind of fun! I'm a bit worried that after getting the razor done it will be fragile enough that it chips out from just shaving though. Fingers crossed!

Then again it might be so hard that it holds an edge practically forever.

Yup, it's probably going to be either-or. We'll know soon enough. The fellow I mentioned earlier that uses the HSS knives uses them at around 15° with a single bevel for paring leather, so I have some amount of hope that the edge will be OK for shaving.

Well, here we go. Besides a bench grinder, this is all I used, so don't give me any lip if it doesn't look superb. Don't have a fancy belt sander so I had to make do with what I've got.



This one's after cutting out the general shape and grinding the periphery.



And here it is after hollow is ground out and the tail tapered. I'd say the razor is between near wedge and ¼ hollow. Next got to drill the hole and make a set of scales.

Ok, hole's in. Started cleaning up the grind marks a bit and prepping for polish. Started setting the bevel for a while too. (A long while! This is going to take some serious time). Included a shot of the grind as well.

Holy moly was drilling that a pain. My drill press is currently out of commission so it was hand drill time. I had to resharpen the drill at least 8 times. (Tungsten carbide drill).



Measures about .005" behind the bevel.