A number of comments have been made about the supposed difference in surface finish between stones that are smoothed by diamond grinding wheels and these stones that grind each other. Diamond is supposed to be better, some say, because it cuts through the grain of the stones and thus produces a smoother surface. I don't think so. If that was the case, and the grains were broken loose by the grinding instead of flattened, the resulting grinding dust would be about as coarse as the grit in the stone. Instead, it is a fine sticky powder, somewhat like flour. I have looked at the surfaces of these stones under my microscope and the grains have flat tops. As I wrote in these comments, the 400 grit stones now feel more like a 1000 of even 2000 grit. I will post some pictures of that in my post section later. Of course, a really good quality stone, especially the right binder and very hard grit produces even better results. Those stones, I have a few, you see them early in this video, will flatten not that easy. [edit] For the photos of the surface see: th-cam.com/channels/VXg03MqlsHsGyxBv4rgMqQ.htmlcommunity?lb=UgkxVd_NtN34YgykZze2zE_C8QE5AYc5RDfX For links to round sharpening stones, try: nl.aliexpress.com/item/1005006391218037.html nl.aliexpress.com/item/1005006394730279.html nl.aliexpress.com/item/1005006858961676.html
For the stones shown on the advert at 1:22 , can you say where they are from as nothing shown on Ebay or Aliexpress. Searched for double sided slip stones with no luck. Thanks
0:40 How would you gauge the pressure needed? If you were to compare it to something.These are the kind of videos we need on youtube! Absolutely incredible
Just light to very light pressure. Say 2 kg and less in this video. I suspect it all depends on the type of stone, and of course the size of the surface. As long as you don't force anything and let the stones do the grinding, it will be fine.
Nice video, very enjoyable watch ^^ I do believe the "whitworth method" was named after whitworth for patenting it, it was used by maudsley before that though. One thing that sets precision machine ground flat stones apart from these is that they will grind partway through the grains of the abrasive, improving the effect of not grinding down a flat surface. I'm sure these work great to tho, I'll give it a try.
very cool process and super easy to achieve Use ful photo's of the differences bewtween stone on stone and diamond honing thanks very much for sharing.
It depends on the grit size, the binder and the hardness. I ground a set of 800 grit stones of silicon carbide a few years ago and that took much longer.
Hi Michael. There are a few forms beyond "concave" and "convex" which can result from grinding. A few of these, particularly the "saddle" form, will match on all 3 stones; that's the reason rotation is required between passes.
thanks for the informative video! Would you mind posting a link to the stones you used, or perhaps some equivalents for those of us that have absolutely no knowledge in that field? :)
It is possible for rectangular stones to gradually go into a "saddle surface" (can Google that to see good images of what I mean) when they are ground against eachother with the longest lengths aligned. That's the reason for using circular (or a regular polygon also works) as the shape: there isn't like one specific direction along which you must align to get equal rubbing of the surface. The overhang would cause it to be very difficult to get equal abrasion across all areas of the surface, which is part of the mathematical assumption that actually makes Whitworth's method work.
@EitriBrokkr In the beginning of the video you see me working with a square flat stone. These can be made well with this method. But rectangular is really a problem. In theory it is possible, but in practice it becomes very difficult. What it is all about is using the symmetry of the surfaces so that each part of a stone is worked equally, so without any preference. That is easy to do with round, hexagonal and square stones, but not with rectangular ones.
What useful application does these small flat surfaces have? TBH constructing your own mirror for an amateur telescope would be a very interesting project, IMHO
See the beginning of the video where I explain the use. Sorry, I built my last telescope 40 or so years ago. After this the light pollution became so bad that I could forget about using a telescope meaningfully. I still have one, which I use occasionally at holydays abroad only.
I enjoyed watching your video, but don't agree that the stones flattened by your process would be the same as the diamond wheel ground ones your photos refer to as being offered at a "hefty price". The difference is that the surface of diamond wheel ground stones is a field of truncated grains, the individual grain tops flattened to be co-planar. On stones flattened by being rubbed together the resulting surface, though flat, is a field that includes sharp grain points because the rubbing action tends to level the surface by fracturing grains instead of cutting through them. Both of the sales listings whose photos you featured (eBay and Kinetic Precision) include photomicrographs showing the nature of the diamond wheel ground surface. Both techniques can produce useful products, but they're not the same and perform differently when used. Thanks for taking the time to make several interesting videos.
The photos Michel uploaded prove you're wrong. Nice flattened tops of the grains and no sign of fractured grains. As a matter a fact, the grounded stones from Norton seem more coarse.
@@Michel-Uphoffcool, I thought it felt a little off. Depending on your goals for the channel, it might be a good idea to start trying your own voice over, ai narration might make things harder.
If you can grind the stones on each other they are usually not good enough to be your flat stones (you need a quality stone with the proper binding agent between the abrasive particles). The flat stone not just only needs to be flat but the particles themselves need to have a flat on top too!! How do I know? Lots of experience ;)
That made no sense. They are abrasive. Do you know how surface plates are made? The practice and method is perfectly sound. Perhaps you should try it yourself.
@@railgap No sense for people who don't have enough understanding on how abrasive stones (or abrasives for that matter) work and function. For a "precision flat stone" to work properly as a flat stone, you need the abrasive particles themselves to be flattened (particle itself needs to be have a ground flat area) on the exposed side. If you don't understand this i'm sorry there's no further discussion I can have with you. The precision flat stone is not a precision flat stone just because its shape is flat, the medium (abrasive) has to be modified too on the exposed side. And since the stone crumbles so easily when rubbed together, I have zero reason to think the abrasive particles are being flattened too - flattened particles are why flat stones create a mirror finish.
@@chronokoks Dead right. The commercial ones are ground for good reason. I made mine in my mill with a diamond wheel. Dresses the wheel, flattens the stones, and leaves the stones so they cannot 'cut' on their flat faces, only their sides.
What a meaningless comment, criticism of something someone cannot change... I imagine you also don't like short people either... because they are short... 🙄😂
A number of comments have been made about the supposed difference in surface finish between stones that are smoothed by diamond grinding wheels and these stones that grind each other. Diamond is supposed to be better, some say, because it cuts through the grain of the stones and thus produces a smoother surface. I don't think so. If that was the case, and the grains were broken loose by the grinding instead of flattened, the resulting grinding dust would be about as coarse as the grit in the stone. Instead, it is a fine sticky powder, somewhat like flour. I have looked at the surfaces of these stones under my microscope and the grains have flat tops. As I wrote in these comments, the 400 grit stones now feel more like a 1000 of even 2000 grit. I will post some pictures of that in my post section later.
Of course, a really good quality stone, especially the right binder and very hard grit produces even better results. Those stones, I have a few, you see them early in this video, will flatten not that easy.
[edit]
For the photos of the surface see:
th-cam.com/channels/VXg03MqlsHsGyxBv4rgMqQ.htmlcommunity?lb=UgkxVd_NtN34YgykZze2zE_C8QE5AYc5RDfX
For links to round sharpening stones, try:
nl.aliexpress.com/item/1005006391218037.html
nl.aliexpress.com/item/1005006394730279.html
nl.aliexpress.com/item/1005006858961676.html
Close enough for anything I do!
For the stones shown on the advert at 1:22 , can you say where they are from as nothing shown on Ebay or Aliexpress. Searched for double sided slip stones with no luck. Thanks
try:
nl.aliexpress.com/item/1005006391218037.html
nl.aliexpress.com/item/1005006394730279.html
nl.aliexpress.com/item/1005006858961676.html
Flatness is the start of all precision
Takes me back to my dad's book on telescope making & the ex WD artillery metalwork that went with it!
Gesundheit Michel.
Very good explanation and how you can get such precision from such cheap stones.
Bravo! 👍💪✌
Geweldig weer Michel !!!!!
Dankjewel
0:40 How would you gauge the pressure needed? If you were to compare it to something.These are the kind of videos we need on youtube! Absolutely incredible
Just light to very light pressure. Say 2 kg and less in this video. I suspect it all depends on the type of stone, and of course the size of the surface. As long as you don't force anything and let the stones do the grinding, it will be fine.
Nice video, very enjoyable watch ^^
I do believe the "whitworth method" was named after whitworth for patenting it, it was used by maudsley before that though.
One thing that sets precision machine ground flat stones apart from these is that they will grind partway through the grains of the abrasive, improving the effect of not grinding down a flat surface. I'm sure these work great to tho, I'll give it a try.
The stones also grind each other's grits to a much finer one. I think the original 400 grit is now well over 1000, the stone feels very smooth.
Excellent tutorial and well explained.
Thank you, I have been thinking about this very idea...... best regards Steve
Very well done and thoroughly explained. Thank you!
very cool process and super easy to achieve
Use ful photo's of the differences bewtween stone on stone and diamond honing
thanks very much for sharing.
These stones are different than any I've seen. What do you search on to find them? Round grinding stones? Thanks for the demonstration.
See the pinned answer.
@@joebabb504 you can search "Whitworth lapping" on Google
Even accounting for your experience, that's still way less time than I expected!
It depends on the grit size, the binder and the hardness. I ground a set of 800 grit stones of silicon carbide a few years ago and that took much longer.
Hi Michael.
There are a few forms beyond "concave" and "convex" which can result from grinding. A few of these, particularly the "saddle" form, will match on all 3 stones; that's the reason rotation is required between passes.
@@wibblywobblyidiotvision Yes, I know. I wouldn't have had any use for a saddle-shaped Newton mirror.
@@Michel-Uphoff I have made several "off axis" mirrors!
@@UncleKennysPlace Off axis Newtonians? Wow! That's asks for way more sophisticated grinding and polishing.
thanks for the informative video! Would you mind posting a link to the stones you used, or perhaps some equivalents for those of us that have absolutely no knowledge in that field? :)
See: nl.aliexpress.com/item/1005006394730279.html
Excellent tutorial
That's great! What was the grit of stones used?
200-400
@Michel-Uphoff Thank you!
This was awesome and far more educational than my metals shop class. Thank you.
Do you think this would be equally succesful with rectangular stones? Or would the shape and the resulting overhang make it impossible?
It is possible for rectangular stones to gradually go into a "saddle surface" (can Google that to see good images of what I mean) when they are ground against eachother with the longest lengths aligned. That's the reason for using circular (or a regular polygon also works) as the shape: there isn't like one specific direction along which you must align to get equal rubbing of the surface.
The overhang would cause it to be very difficult to get equal abrasion across all areas of the surface, which is part of the mathematical assumption that actually makes Whitworth's method work.
@EitriBrokkr In the beginning of the video you see me working with a square flat stone. These can be made well with this method. But rectangular is really a problem. In theory it is possible, but in practice it becomes very difficult. What it is all about is using the symmetry of the surfaces so that each part of a stone is worked equally, so without any preference. That is easy to do with round, hexagonal and square stones, but not with rectangular ones.
Speed running precision manufacturing
Brilliant!
What useful application does these small flat surfaces have?
TBH constructing your own mirror for an amateur telescope would be a very interesting project, IMHO
See the beginning of the video where I explain the use. Sorry, I built my last telescope 40 or so years ago. After this the light pollution became so bad that I could forget about using a telescope meaningfully. I still have one, which I use occasionally at holydays abroad only.
If you used a fluid to make a slurry of the dust, would these have created a more polished surface? (Same as using water stones for sharpening blades)
Probably, but I liked to keep the stones dry.
Use glass plates instead and polish them to 1/20 of a wavelength green light (~26nm) accuracy, I have done it several times.
And then? The stones need to stay abrasive.
I enjoyed watching your video, but don't agree that the stones flattened by your process would be the same as the diamond wheel ground ones your photos refer to as being offered at a "hefty price". The difference is that the surface of diamond wheel ground stones is a field of truncated grains, the individual grain tops flattened to be co-planar. On stones flattened by being rubbed together the resulting surface, though flat, is a field that includes sharp grain points because the rubbing action tends to level the surface by fracturing grains instead of cutting through them. Both of the sales listings whose photos you featured (eBay and Kinetic Precision) include photomicrographs showing the nature of the diamond wheel ground surface. Both techniques can produce useful products, but they're not the same and perform differently when used. Thanks for taking the time to make several interesting videos.
Se the pinned comment. I will post my photos very soon.
The photos Michel uploaded prove you're wrong. Nice flattened tops of the grains and no sign of fractured grains. As a matter a fact, the grounded stones from Norton seem more coarse.
Did you use AI narration?
Yes. English is not my native tongue. See the about section of this channel.
@@Michel-Uphoffcool, I thought it felt a little off. Depending on your goals for the channel, it might be a good idea to start trying your own voice over, ai narration might make things harder.
@@edwardnardella6854 I will only do that if almost anybody understands Dutch.
If you can grind the stones on each other they are usually not good enough to be your flat stones (you need a quality stone with the proper binding agent between the abrasive particles). The flat stone not just only needs to be flat but the particles themselves need to have a flat on top too!! How do I know? Lots of experience ;)
That made no sense. They are abrasive. Do you know how surface plates are made? The practice and method is perfectly sound. Perhaps you should try it yourself.
@@railgap No sense for people who don't have enough understanding on how abrasive stones (or abrasives for that matter) work and function. For a "precision flat stone" to work properly as a flat stone, you need the abrasive particles themselves to be flattened (particle itself needs to be have a ground flat area) on the exposed side. If you don't understand this i'm sorry there's no further discussion I can have with you. The precision flat stone is not a precision flat stone just because its shape is flat, the medium (abrasive) has to be modified too on the exposed side. And since the stone crumbles so easily when rubbed together, I have zero reason to think the abrasive particles are being flattened too - flattened particles are why flat stones create a mirror finish.
@@chronokoks Dead right. The commercial ones are ground for good reason. I made mine in my mill with a diamond wheel. Dresses the wheel, flattens the stones, and leaves the stones so they cannot 'cut' on their flat faces, only their sides.
See the pinned comment.
"Lots of experience.." 🤭 The tops are flat. See the photo's.
Good ideas, bad voice...
Yours is better (when you have to speak Dutch) ? 😂
What a meaningless comment, criticism of something someone cannot change... I imagine you also don't like short people either... because they are short... 🙄😂