Make your own precision ground flat stones with a pencil

In this short video I grind three perfectly flat toolroom stones with the aid of a pencil and at the costs of 10 dollars and some elbow grease. Enjoy!
Sorry, no music this time. Too much to tell..

[@Michel-Uphoff]

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 instead of breaking them out 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. As far as I can tell, there is no real difference between silicon carbide or aluminium oxide and diamond when it comes to achieving a very flat smooth surface. The carbide or carborundum breaks into smaller and smaller pieces and grinds the surface of each protruding grit flatter and flatter, and it may even polish the surface of the stone eventually. Of course, diamond lasts much longer (but diamond wears out too) . I have looked at the surfaces of these stones under my microscope and the grains have nice flattened tops. As I wrote in these comments, the 400 grit stones now feels 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 one with a very even grain size and a strong binder produces even better results. Those stones, I have a few, you see them early in this video, will however flatten not that quickly. [edit] For the photos of the surface see: kzbin.info/door/VXg03MqlsHsGyxBv4rgMqQcommunity?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

[@1crazypj]

I agree with you. When using grinding wheels, the speed of truing diamond changes the surface finish of wheel. Fast traverse gives coarse wheel, slow traverse with multiple passes can make an 80 grit wheel act and finish like a 600 grit wheel.

[@thejoetandy]

ex car detailer here, there is evidence that aluminium oxides break down into smaller crystals with use; for the majority of oxides used in abrasives. It's likely the top surfaces have been clogged/filled with finer abrasives explaining the feeling somewhat

[@subterraniantool846]

Diamond wheel grinding produces a very uniform field of truncated abrasive grains - flat co-planar tops with sharp edges. Surface smoothness depends on the wheel grit, grinding equipment and technique. I don't think of whole grains being broken loose when rubbing together stones with a proper bond, but of small grain fragments instead. As thejoetandy's reply asserts, aluminum oxide grains break down into smaller crystals exposing new, sharp cutting surfaces. That's why an AlOx sharpening stone continues to cut as it wears. Hence the flour-like nature of the swarf, I'm not sure of the particle size. I filter the swarf-containing coolant from diamond wheel stone grinding with a 25 micron pre-filter and a 5 micron final filter.

[@typograf62]

A solution that I did not know to a problem I did not know. And extremely fascinating!

[@cnctroubleshooting9052]

Came up as a random suggestion on my KZbin feed. Pretty cool and useful, thanks.

[@sdrc92126]

Flatness is the start of all precision

[@rjung_ch]

Gesundheit Michel. Very good explanation and how you can get such precision from such cheap stones. Bravo! 👍💪✌

[@johnlambo135]

Geweldig weer Michel !!!!!

[@Michel-Uphoff]

Dankjewel

[@Kineth1]

Very well done and thoroughly explained. Thank you!

[@ryebis]

Excellent tutorial and well explained.

[@scottmerritt9877]

The key message of the video is to use three surfaces and be systematic. The video explains some but not all of the key factors in flatness. It does not address smoothness. I appreciate this effort to teach. And I suggest checking the result with an interferometer.

[@AndreasBauer12]

Yes, of course. An interferometer. A typical gadget for the home shop, costs as much as a car, but a hobby may cost something, right? Does he have to scan the surface of every grain to be sure none are sticking out? And why should he do that? Doesn't this three-plate method, if applied correctly, ALWAYS lead to a perfect plane?

[@Michel-Uphoff]

See the photo's I uploaded for the smoothness of these (and other) stones.

[@butsukete1806]

@Andreas-Bauer21 Optical flats work perfectly fine as an interferometer for this purpose and aren't that expensive. You just tip it and see if the lines are straight.

[@michaelhompus2475]

@Andreas-Bauer21 I even wonder if an interferometer is capable of picking up a good reflection off of a grainy stone?

[@jrkorman]

Close enough for anything I do!

[@stevenhavener7327]

Thank you, I have been thinking about this very idea...... best regards Steve

[@wibblywobblyidiotvision]

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.

[@Michel-Uphoff]

@@wibblywobblyidiotvision Yes, I know. I wouldn't have had any use for a saddle-shaped Newton mirror.

[@UncleKennysPlace]

@@Michel-Uphoff I have made several "off axis" mirrors!

[@Michel-Uphoff]

@@UncleKennysPlace Off axis Newtonians? Wow! That's asks for way more sophisticated grinding and polishing.

[@terrylembke8100]

Thanks for this video . The Whitworth method works . A MAN WITH AN EXPERIENCE IS NEVER AT THE MERCY OF A MAN WITH A THEORY .😮

[@pcka12]

Takes me back to my dad's book on telescope making & the ex WD artillery metalwork that went with it!

[@TalRohan]

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.

[@ikkiiiieee]

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

[@Michel-Uphoff]

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.

[@niemanddings9517]

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.

[@Michel-Uphoff]

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.

[@argee55]

Brilliant!

[@EverettWilson]

Even accounting for your experience, that's still way less time than I expected!

[@Michel-Uphoff]

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.

[@eddietowers5595]

This was awesome and far more educational than my metals shop class. Thank you.

[@mparkerlisberg]

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

[@Michel-Uphoff]

try: nl.aliexpress.com/item/1005006391218037.html nl.aliexpress.com/item/1005006394730279.html nl.aliexpress.com/item/1005006858961676.html

[@nedisawegoyogya]

Speed running precision manufacturing

[@michaelhompus2475]

Lijkt op 'een spelletje balletje balletje' wat ik in achteraf-straatjes in grote stend heb gezien zoals je die stenen heen en weer verplaatst. :-). Je hebt, begrijp ik, ook wel eens telescoop spiegel geslepen. Tool of mirror on top (TOT/MOT) bepaalt welke bol wordt. Dat weet ik, maar dat je in de eerste ronde A op B legt en vervolgens B op A zonder tussendoor de vlakheid te meten begrijp ik niet. Wanneer stop je met die stap(pen)? Als je netjes slijpt (W-slagen, beide stenen roteren etc.) blijven A en B goed op elkaar passen maar kunnen beslist minder vlak (hol/bol) zijn dan voordat je begon?

[@Michel-Uphoff]

De video legt een principe uit. Het is geen volledig verslag van alle ronden en iedere tussentijdse meting. Dat zou maar een saaie bedoening opleveren.

[@Trainwreck1123]

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? :)

[@Michel-Uphoff]

See: nl.aliexpress.com/item/1005006394730279.html

[@russellhayward2359]

Excellent tutorial

[@joebabb504]

These stones are different than any I've seen. What do you search on to find them? Round grinding stones? Thanks for the demonstration.

[@Michel-Uphoff]

See the pinned answer.

[@ivolol]

@@joebabb504 you can search "Whitworth lapping" on Google

[@EitriBrokkr]

Do you think this would be equally succesful with rectangular stones? Or would the shape and the resulting overhang make it impossible?

[@danielkruyt9475]

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.

[@Michel-Uphoff]

@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.

[@ivolol]

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

[@Michel-Uphoff]

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.

[@kenwheeler-do9ov]

Thanks for the video Michel. What grain size were the three stones that you used?

[@jansuchomelLBC]

That's great! What was the grit of stones used?

[@Michel-Uphoff]

200-400

[@jansuchomelLBC]

@Michel-Uphoff Thank you!

[@ErikBongers]

I still wonder if the stones flattened by this method would be similar enough to the ones ground with a wheel. Perhaps the flat areas created with this method have rounded edges while with a wheel the flats have sharper edges. If that's true, there should be a difference in abrasive action. The ones ground with a wheel should be more aggressive in removing small metal bumps. Not saying that is the case - just wondering.

[@michaelhompus2475]

Flatness achieved by a machine is limited to the flatness of the machine. The three-surfaces method is at least mathematically better, especially over a larger surface area. Can a wheel grinder produce sub-micron accuracy? In optics, wavelength/10 is a normal requirement. That comes down to 50 nm or so. Wheel grinders achieve a few microns at best?

[@subterraniantool846]

I have found differences in the cutting action which I ascribe partially to diamond wheel grinding producing truncated grain points with sharper edges as you suggest. Small swellings from scratches on a ground surface were more quickly removed. Another factor may be the number of cutting edges produced. In diamond wheel grinding the complete surface is ground somewhat below the minimum required to produce a flat stone surface. The machine removes material effortlessly, cleanly truncating every grain at the plane's surface. Comparing the Michel Uphoff's great photomicrographs, I wasn't sure the hand rubbing process produced the same fully populated field of cutting edges. More info needed to draw a conclusion. I prefer the diamond wheel ground stones' cutting effectiveness, the localized bright mirror finish left at the edges where the swelling around scratches and dings has been removed, and the complete lack of scuffing on the surrounding machined surface. But if you have the time to make them, carefully hand ground round stones can get the job done at a lower out-of-pocket cost than the $90 US for diamond wheel ground stones delivered in the US.

[@alt3241]

Thanks , I am sure I can make a robot that can do this .

[@JohnColgan.]

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)

[@Michel-Uphoff]

Probably, but I liked to keep the stones dry.

[@subterraniantool846]

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.

[@Michel-Uphoff]

Se the pinned comment. I will post my photos very soon.

[@AndreasBauer12]

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.

[@MegaDevilmaycare]

This is possibly the best reasoned and evidenced argument I've ever seen presented in a KZbin comments section.

[@guitarchitectural]

​@@MegaDevilmaycareand based on the photos posted... He's wrong. 🤷‍♂️

[@bussi7859]

Use glass plates instead and polish them to 1/20 of a wavelength green light (~26nm) accuracy, I have done it several times.

[@Michel-Uphoff]

And then? The stones need to stay abrasive.

[@edwardnardella6854]

Did you use AI narration?

[@Michel-Uphoff]

Yes. English is not my native tongue. See the about section of this channel.

[@edwardnardella6854]

​@@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.

[@Michel-Uphoff]

@@edwardnardella6854 I will only do that if almost anybody understands Dutch.

[@chronokoks]

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 ;)

[@railgap]

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.

[@chronokoks]

@@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.

[@paulbonser5892]

@@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.

[@Michel-Uphoff]

See the pinned comment.

[@AndreasBauer12]

"Lots of experience.." 🤭 The tops are flat. See the photo's.

[@michaelhansen6481]

🤘🤘👍👍🤪

[@Festivejelly]

Interesting but had to downvote for the ai voice.

[@AndreasBauer12]

Yes, every now and then there are that people. They are more interested in appearances than substance. They do not realize that their language is not spoken by everyone without problems. They do not realize that a creator therefore makes an extra effort to be completely understandable to them. They also do not understand that if you find an AI voice uncanny, they can turn on the subtitles. They do not make any effort to think about the reasons why someone else does it the way he/she does,.

[@michaelhompus2475]

@Andreas-Bauer21 Gutes Kommentar. Ja, und diese Leuten wie @Festivejelly, fahren mit Hilfe von Google Maps?... die Beraterin ist wohl echt oder? Uphoff makes an effort to be understandable, which I can not say of all native speakers on YT if I see the automatically generated English subtitles.

[@Michel-Uphoff]

@Festivejelly: I think that's a shame, and if I'm honest, it's also unnecessary. English is not the native language of everyone who watches KZbin. I suspect that your native language is English and that AI voice makes you somewhat uncanny. Imagine the following: KZbin is mainly German-speaking. You do understand it, but it takes you way more effort than a German, and that's not your fault. Now a video comes along from a Frenchman, and he starts speaking German with a thick French accent. Ten to one that you now understand a lot less of it, and if you turn on the subtitles, it doesn't help because it can't handle accents. Now a German comes along (who has little trouble understanding German with a thick French accent), and downvotes the video because of the extra effort the creator has made to be understandable *for everyone*.