The dark art of diamond sharpening

[Estrada]

CVD diamond blanks are actually quite cheap. I think the most I've paid is about USD$15.00 a piece including taxes and shipping, and I have bought some much cheaper than that too.

[Dub Studio]

Great thread guys!

BTW there is a great series of Youtube tutorials on cutting diamond styluses by Jignesh Rokad on the Excel Enterprise channel... I think they are the same guys that make the dops / tangs mentioned earlier.

https://www.youtube.com/watch?v=Hjg1lNwwhOY

[substage]

You need your disc to look like this.

I'm trying to get to grips with that a prepared scaife should look like, can I ask, if this photo taken as it is spinning?

I've been experimenting with different surface preparations before charging my cast iron. Yesterday I tried cleaning it with acetone and soapy water, then applying ferric chloride as it was (slowly) spinning, with the thought that this would provide some micro-pores for the diamond grit to sit.

I've tried mashing it in with a piece of brass, which I was expecting to change the colour of the scaife somewhat, however the brass colour only appeared after I decided it had failed and I cleaned with, then reapplied ferric chloride.

Here is the wheel pre-etching;

PreEtch.jpg

Here it is after the first etch (about 5 minutes of ferric chloride on the surface)
Etch1.jpg

Here it is after the second etch
Etch2.jpg

Here it is after I added a paste of W5 grit mixed with vaseline, pressed it in with a 20mm bearing on an 8mm rod and wiped it off with a cloth
483686481_1325937148627194_4730407760227855086_n.jpg

I haven't tried shaping a diamond on it yet, as I am waiting for these to arrive;
PinVice.png

I'd love to buy a proper dop, but at the moment I'm a bit broke, I'd prefer to get a little bit more confidence and cash before I make the jump, I believe I can adapt this to a thread which should give me a reasonable amount of gripping strength while hopefully sinking some heat from the grinding process and furthermore hopefully prove some viability in my methods.

Keep in mind I'm intending to make a second machine for the final polishing stage, which will be free from contamination from coarser grits. (I'm looking at W0.2 grit for that stage)

Hello friend, where can I find this piece that is fixed and has the possibility of giving the correct angle of 45 degrees to sharpen the diamond?

[Dub Studio]

Not an expert, but is that not the dop and tang?

[Stylus Maker]

Cant remenber if scaife is spinning or stationary. They look the same.The dop and tang I use came from HDPT in India. It was about$180USD plus shipping.

[classd2008]

CVD diamond blanks are actually quite cheap. I think the most I've paid is about USD$15.00 a piece including taxes and shipping, and I have bought some much cheaper than that too.

Thanks for sharing, and I'm following along. Could you tell me how your project turned out and where you bought the CVD diamond blanks?

[classd2008]

@Estrada Could you share more photos of your polishing machine, such as the motor parts and how you disposed of the bearings?

[PhilFW]

Hi

I'd really like to try get my head around the necessary angles for the grinding. I have a Vevor lapping machine and have been experimenting with polishing sapphire and CVD diamond.
I just don't have the topological mind to visualize the process. I can set the index wheel to produce 90 a degree tip.. but the chisel profile of a stylus has the relief angle also. I guess there must be a preferred order to the cuts.

cheers
Phil

[zdenek]

Hi

I'd really like to try get my head around the necessary angles for the grinding. I have a Vevor lapping machine and have been experimenting with polishing sapphire and CVD diamond.
I just don't have the topological mind to visualize the process. I can set the index wheel to produce 90 a degree tip.. but the chisel profile of a stylus has the relief angle also. I guess there must be a preferred order to the cuts.

cheers
Phil

I've included a link to a company that doesn't hide anything about its work. Everything is visible, from the lapping of the discs, to the type of diamond discs, to the grinding machine [diamond cutter], microscopes, vises, clamps, and the process of grinding the diamond cutter itself. Nothing is hidden. It's not as simple as grinding gemstones, including natural diamonds, on a horizontal disc; it's a much more advanced art.

Let me just tell you that making a diamond cutter for cutting master slabs [lacquered or copper] is the ultimate driving school in this field.

I told you I make my own diamond cutters. Out of 10 cut CVDs, I manage to make two reasonably well and capable of cutting slabs. Out of 20 cut pieces, I manage to make one perfectly, masterfully. Watch these Soviet films, the guy doesn't hide anything [he's probably tired of doing this, I think, and is looking for successors in this field of art] :)https://www.instagram.com/p/CsTNcCAgfWG/

[zdenek]

video Soviet https://www.instagram.com/p/CsTNcCAgfWG/
Diamond Knife
[There will be a third NINGA warhead, which will sail east to Oceania and New Zealand completely free of charge and with shipping, and this is not a joke, [it will not hang in the customs office this time, like that German clone...]

[Estrada]

I think there are many ways of approaching the cutting angles, but this is how I do it.

I set up the my my faceting tool so that there is an angle of 40.89 degrees between the diamond and the scaife. This achieves a 90 degree tip with a back angle of 30 degrees. I worked backward from this to get the angle of 40.89. To set this up I made a guide on my 3D printer.

Screenshot 2024-05-01 at 6.38.23 PM.png

Screenshot 2025-02-03 at 8.21.35 PM.png

Note that the red surface is the mirror face

Next, rotate the diamond 60 degrees along its axis

Screenshot 2025-02-03 at 8.23.13 PM.png

Cut the first facet

Screenshot 2025-02-03 at 8.24.19 PM.png

Now rotate 60 degrees in the opposite direction from starting position

Screenshot 2025-02-03 at 8.28.06 PM.png

Cut second facet

Screenshot 2025-02-03 at 8.28.47 PM.png

Result

Screenshot 2025-02-03 at 8.29.36 PM.png

Obviously there will be some back and forth between these angles as you work your way from rough shaping to polishing, but these are the settings I generally use.

I hope that is helpful

[Estrada]

video Soviet https://www.instagram.com/p/CsTNcCAgfWG/
Diamond Knife
[There will be a third NINGA warhead, which will sail east to Oceania and New Zealand completely free of charge and with shipping, and this is not a joke, [it will not hang in the customs office this time, like that German clone...]

Sounds great! I look forward to it

[markrob]

Hi Everyone,

I also have a Vevor machine, but I am for now, just fabricating embossing styli using 1/16" drill blanks of HSS, tungsten, or Carbide. I was running into the same issue of trying to get my head around the geometry. I ended up using Gemini AI to derive a formula and and simple calculator program to get the machine settings given the included facet angle and back angle desired. I was able to validate the results of the AI generated formulas by constructing a replica of the Vevor machine in Fusion 360 and verifying that the angles created match the calculated values. The AI created a simple html file that will run on any modern web browser. See the attached file.

Vevor.zip

Note that the included angle of the facets is not the angle that presented normal to the flat front face. To get Estrada's geometry, enter an included angle of 98 degrees and a back angle of 30 and you will get his rotation and elevation. In my case, there is no flat front face as I am starting with a round drill blank. I am also rotated 180 degrees from the way you would orient a cutting styli. I can supply a link to the AI conversation if you want to see the derivation of the equations. Hope you find this of some help.

Mark

[markrob]

Hi Again,

I decided to see if the AI could derive the formula to create the desired front angle. In my case, since the front face is cylindrical, it calculated a projection. In the case of a square shank, I think the numbers will hold. This update Its seems to be correct, but I will do some testing. The results agree with Estrada's numbers. See the attached file.

Vevor 2.zip

Mark

[PhilFW]

I'm interested to see what others have to say on this topic - I tried using ceramic bonded discs, but found the removal rate was too slow - or maybe I'm too impatient, as it seems like Estrada is getting usable results with a bit of patience...

Hi
I have a terribly simple question....
Using a faceting post.. what angles are used?
I can understand setting the angle at 45 for each side.
To achieve the 15 degree rake is it best to cut the end of the diamond chip first and then make the 90 degree angle afterwards?

I keep trying to simulate it in 3d and I get a 90 degree edge but the rake is absen or the two 45 degree planes don't meet in a straight edge (???)

I am missing something....

cheers

Phil

[Estrada]

I'm interested to see what others have to say on this topic - I tried using ceramic bonded discs, but found the removal rate was too slow - or maybe I'm too impatient, as it seems like Estrada is getting usable results with a bit of patience...

Hi
I have a terribly simple question....
Using a faceting post.. what angles are used?
I can understand setting the angle at 45 for each side.
To achieve the 15 degree rake is it best to cut the end of the diamond chip first and then make the 90 degree angle afterwards?

I keep trying to simulate it in 3d and I get a 90 degree edge but the rake is absen or the two 45 degree planes don't meet in a straight edge (???)

I am missing something....

cheers

Phil

Hi Phil,

I think I'm using the same faceting post as your Vevor machine, in any case below is a photo of the post I'm using.

IMG_7441.JPG

You can also see in this photo a black 3d Printed Guide I have. The sloping surface of this gives me the 40.89 degree angle I need to for my geometry to work. I simply sit it on top of the lap and adjust the angle of the arm to suit this. I have a 96 click index wheel on this. I start out with the wheel on 0degrees and have the mirror face facing upwards (i.e horizontal/level if you were to lift the arm up to horizontal). I'm then rotating 60 degrees either side of 0 for each facet. This corresponds to points 16 and 80 on the index wheel (16 clicks either direction. Each click is 3.75 degrees, 3.75 x 16 = 60).

Hope that helps

[PhilFW]

Brilliant answer! Thanks Estrada

I'll give it a try!

[Estrada]

Brilliant answer! Thanks Estrada

I'll give it a try!

Good luck Phil, let us know if you have success

[Estrada]

As a little aside from making diamond styli, I also had a go at making my own sapphire cutting styli a while back. I managed to find a source of sapphire rods which are about 0.7mm diameter. Since I'm starting with a rod, the first step was to create a flat mirror surface. I'm pretty sure I did this simply by rubbing the sapphire rod back and forth on my 50,000 grit resin bond lap until I got a flat surface. I think it took a while but eventually got there. No way You'd be able to do that with a diamond but because sapphire is so much softer it seemed to work pretty well and I managed to get a face that was pretty even in width along the length of the rod. Here is the final result

Photo on 5-04-26 at 12.15 PM.jpg

Photo on 5-04-26 at 12.22 PM.jpg

Photo on 5-04-26 at 12.23 PM.jpg

I've tried to show the burnishing facets but my digital scope is cheap crap so the resolution isn't so good. They are there and are somewhere between 3 and 5 microns wide. I think one facet is a bit wider than the other, they were done by eye so not quite as accurate as it could be.
I used two different geometries for grinding - one for the main facets, one for the burnishing facets. I started by grinding the main facets, essentially the same process as grinding a diamond with sharp edges. I then reset the faceting device to the geometry for the burnishing facets. The burnishing facets are ground with the lapping machine off and gently stroking the gem across the surface, it really doesn't take long to remove the material. I formed the burnishing facets a bit larger than required, then went back to the first geometry and ground these until the burnishing facet got smaller and smaller. My hand held scope I use for working with has a reticle which measures in 5 micron increments. I basically aimed to get the facet just smaller than one division.

I tested it a while back but it seemed a bit noisy, though I don't think I was using stylus heating. I finally got my stylus heating working (well working better) today so I gave it another test and it seems to work. Reasonably quiet groove, though there is a bit of noise if you really crank the volume. The lacquers I'm testing with are also quite old and the surface isn't perfect so that probably does not help. I'm keen to see if I can replicate this on a diamond at some point, I'm sure it will be much more difficult. I've read that diamond creates more static than sapphire which could be an issue. Not quite sure how this could be solved.

[Estrada]

A quick photo showing both modulated and unmodulated grooves in the lacquer. You can see a lot of very fine scratches on the surface of the lacquer - it's an old one for experimenting. Still plays back reasonably. The grooves are probably a bit wide, around 3.8 mil. I set stylus weight to 25g so could probably be a bit lighter.

Photo on 5-04-26 at 7.20 PM.jpg