Stoning the table with a 100 grit stone?
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    Quote Originally Posted by kvid View Post
    Please someone explain to me how stoning the table on a VMC with a 100 grit stone makes sense? My question relates to the attached video.

    100 grit just seems too rough.

    Well that stone does have a fine and course side, but anyways. Take a 3-4" '100 grit stone' and try and wipe a .001" hole in a flat ci surface, youre gona be a while.

    Aluminium oxide wins all day for deburring.

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    I'm all for stoning tables and the bottoms of things that go on them, but he really should have mentioned in that video to flatten the stone before using it. That 4" diameter stone WILL remove a lot of material if it's only hitting on a couple points. Using one that way is bad news, the small contact area in such a case increases the local pressure immensely.

    And I have had that exact same stone for decades. I never use the coarse side on a machine table, the fine side is plenty good enough even after it's flattened on a diamond plate or with a diamond wheel on a surface grinder and not cutting aggressively.

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    I have a set of ground flat-stones I purchased about 30 years ago. I use the course side on the table if something gets dropped that caused the burr. First, I use a burr file then finish with the course side of the flat-stone.

    I believe these are made from Norton India combination stones having 150 course and 400 fine grits. The fine side only gets used on gage blocks after stoning with the course side.

    Edit: Ok. I just watched the video and eKretz is right. They did not mention that the stones should be precision ground before using. The stone he is using appears to be silicon carbide. I've never used anything but Aluminum Oxide (India) stones. And I only use Isopropyl Alcohol when I stone the surfaces. I've heard of folks using kerosene. Perhaps oil may be appropriate for the silicon carbide stones. I'll stick with Alcohol.

    Best Regards,
    Bob

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    Quote Originally Posted by rjs44032 View Post
    I have a set of ground flat-stones I purchased about 30 years ago. I use the course side on the table if something gets dropped that caused the burr. First, I use a burr file then finish with the course side of the flat-stone.

    I believe these are made from Norton India combination stones having 150 course and 400 fine grits. The fine side only gets used on gage blocks after stoning with the course side.

    Edit: Ok. I just watched the video and eKretz is right. They did not mention that the stones should be precision ground before using. The stone he is using appears to be silicon carbide. I've never used anything but Aluminum Oxide (India) stones. And I only use Isopropyl Alcohol when I stone the surfaces. I've heard of folks using kerosene. Perhaps oil may be appropriate for the silicon carbide stones. I'll stick with Alcohol.

    Best Regards,
    Bob
    You use a 150 grit stone on gage blocks??

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    Quote Originally Posted by Mike1974 View Post
    You use a 150 grit stone on gage blocks??
    Maybe his angle grinder is broken ?

    Regarding stones, I wouldn't use anything less than 200 grit or more than 400 grit on a table. We used Paraffin ( Kerosene in the USA ? ) as a lubricant.

    Regards Tyrone.

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    Quote Originally Posted by Mike1974 View Post
    You use a 150 grit stone on gage blocks??
    Yep! The only time I need to stone a gage block is when they are dinged and burred or corroded. A burr file will not work on a hardened gage block well. The fine grit on my stone is not used to knock burrs down. Only to finish the process.

    Remember these are precision ground stones, not off the shelf combi-stones. They cost $300 for a set back in the 90s. Used properly, I could stone gage blocks all day with the coarse side of the stone and remove no material, Unless there is a burr. That is why we use them - to knock down the burrs while preserving the original flat surfaces.

    By the way, I have been able to take severely nicked or corroded gage blocks that will not wring and have them ring post stoning.

    Don't just take my word for it. See what Starret / Webber says: Stoning Gage Blocks

    Best Regards,
    Bob

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    I like mineral spirits for lubricant while stoning. Keeps the stone from loading and pinning very well. I would imagine Tyrone's kero would work just the same.

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    I spose my fav AO stone is 3x6ish, maybe 5/8 thick. I like to clean it on a diamond lap I made for granite flat lapping, it cuts it like butter. Ive not tried to measure the stone for flatness per say, but itll suck to a surface plate if left wet. When used with mineral spirits itll float over a surface unless theres a burr, then itll grab and cut very positively, I mainly used it for scraping when there was space.
    Im not sure 'grit grade' is so relevant if surfaced with diamond, could be wrong, and were talking about kissing burrs out of a table, not stoning the shit out of it.

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    I got my supply of stones from a company I worked at that did on site rubber mill and calender roll honing. They bought the stones from " Norton " back in the day. The stones were about 6" long by about 2-1/2" wide at the bottom tapering to 2" at the top. They were about 2-1/2" high. The taper was to facilitate holding them securely in the honing rig.

    They were a real nice fit in your hand. For rubbing down tables and fired up ways they were perfect. Give them a good 5 minute rub on a big machine table along with a squirt of paraffin and the bottom of the stone would wear perfectly flat.

    Most of the stones were 200 grit for roughing the rolls, then 400 grit for finishing them. Occasionally they would use 600 grit, and sometimes they used diamond powder impregnated blocks.

    Everytime I visited the company I got a couple. I gave the ones I had away when I called it a day. I've scoured various internet sites, including " Norton ", and I've never been able to see any like them for sale. Maybe they were a special order.

    Regards Tyrone.

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    If you have not used precision ground stones, then you can't know just how they operate. I didn't until I got a pair.

    Regular stones have a grit that is described by a number. So 100 grit is coarser then 400 grit. And if you rub two 100 grit stones together, they will abrade each other and fresh particles of the abrasive will be exposed. And you can feel the grit of the stones. The same is true for 400 grit or any other grit. This is the case, even if they have been flattened in a normal manner which includes everything from rubbing them on the sidewalk to using another stone that is designated for that process to using a diamond plate to flatten them. Any and all of these flattening processes will remove particles of abrasive in order to flatten them. But all of these flattening processes will be exposing fresh grains of abrasive WITH SHARP EDGES.

    Precision ground stones are not just flattened. They are also ground SMOOTH. The abrasive grains are not broken off to expose new ones. They are ground flat. Let me say that again, THE GRAINS OF ABRASIVE ARE GROUND FLAT. They do not have any exposed sharp edges. All the ground faces of the abrasive are flat and parallel and co-plainer (in the same plane).

    So when you rub two precision ground flat stones together you do not remove any abrasive grains. They GLIDE across each other much like two surfaces of a journal bearing will glide over each other. You do rub them together before each use and that is why they are sold in pairs. But this is not to expose fresh abrasive. It is to remove any bits of metal or dust or other foreign substance that sit above the plane of the ground faces of the abrasive. You are really just reestablishing that same flat surface that was originally ground into them when they were made.

    And when you rub them across a metal table, the same thing happens. They only remove things that stick above the flat surface of that table. Once that has been done, no matter how hard you rub, they do not remove anything more. They only restore the original flat surface of the table.

    And in use, there is little difference between a 100 grit and a 400 grit precision ground flat stone. My pair have coarse and fine sides and there is no clear difference in how they act on a flat surface or when they are rubbed together. Even when I rub the coarse side of one with the fine side of the other there is little difference between that and rubbing the same sides together. They aren't just sidewalk flat. They are ground flat.

    I have come to realize that you should NOT stone a flat table or any other surface that is supposed to be flat with an ordinary stone, even one that has been flattened with ordinary means. You should only stone a flat table with precision ground flat stones. The other side of this is that precision ground flat stones are not to be used to flatten a surface. They are only a final, finishing touch to a surface that is already flat. That is the way it is in my shop and I am sticking to it.

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    As for the stones used on gauge blocks, I suspect they are a high quality version of the precision ground flat stones. But I do not know this as a fact.

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    Quote Originally Posted by EPAIII View Post
    As for the stones used on gauge blocks, I suspect they are a high quality version of the precision ground flat stones. But I do not know this as a fact.
    Mitutoyo offers a precision abrasive block they call "Cerastone", and at a very tidy price too:

    Mitutoyo Cerastone, 150 x 50 x 20mm - 601644 - Penn Tool Co., Inc

    They claim it's for both steel and ceramic gauge block repair, among other "precision" uses.

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    EPAIII,

    Thanks for clarifying for the un-initiated rabble who sought to ridicule. My stones came from Professional Instruments Co. back in the 90s. They are ground-flat and come in pairs. They are much more common today than they were back then. So I was a bit surprised by the push back.

    Best Regards,
    Bob

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    Quote Originally Posted by EPAIII View Post

    Regular stones have a grit that is described by a number. So 100 grit is coarser then 400 grit. And if you rub two 100 grit stones together, they will abrade each other and fresh particles of the abrasive will be exposed. And you can feel the grit of the stones. The same is true for 400 grit or any other grit. This is the case, even if they have been flattened in a normal manner which includes everything from rubbing them on the sidewalk to using another stone that is designated for that process to using a diamond plate to flatten them. Any and all of these flattening processes will remove particles of abrasive in order to flatten them. But all of these flattening processes will be exposing fresh grains of abrasive WITH SHARP EDGES.

    Precision ground stones are not just flattened. They are also ground SMOOTH. The abrasive grains are not broken off to expose new ones. They are ground flat. Let me say that again, THE GRAINS OF ABRASIVE ARE GROUND FLAT. They do not have any exposed sharp edges. All the ground faces of the abrasive are flat and parallel and co-plainer (in the same plane).
    You have part of this wrong. Flattening a hone on a diamond plate does the EXACT SAME THING as the diamond grinding wheel. In your mind diamond cuts the abrasive particles of the hone when it's bound in a grinding wheel but not when it's on a diamond plate? Not sure how you arrived at that conclusion... But having personally used both methods to flatten hones, they work out the same. The diamond plate knocks the abrasive particles flat just the same as the diamond grinding wheel. This is effectively glazing the hone. And yes it does make it act as though it were a finer hone.

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    Quote Originally Posted by EPAIII View Post
    If you have not used precision ground stones, then you can't know just how they operate. I didn't until I got a pair.

    Regular stones have a grit that is described by a number. So 100 grit is coarser then 400 grit. And if you rub two 100 grit stones together, they will abrade each other and fresh particles of the abrasive will be exposed. And you can feel the grit of the stones. The same is true for 400 grit or any other grit. This is the case, even if they have been flattened in a normal manner which includes everything from rubbing them on the sidewalk to using another stone that is designated for that process to using a diamond plate to flatten them. Any and all of these flattening processes will remove particles of abrasive in order to flatten them. But all of these flattening processes will be exposing fresh grains of abrasive WITH SHARP EDGES.

    Precision ground stones are not just flattened. They are also ground SMOOTH. The abrasive grains are not broken off to expose new ones. They are ground flat. Let me say that again, THE GRAINS OF ABRASIVE ARE GROUND FLAT. They do not have any exposed sharp edges. All the ground faces of the abrasive are flat and parallel and co-plainer (in the same plane).

    So when you rub two precision ground flat stones together you do not remove any abrasive grains. They GLIDE across each other much like two surfaces of a journal bearing will glide over each other. You do rub them together before each use and that is why they are sold in pairs. But this is not to expose fresh abrasive. It is to remove any bits of metal or dust or other foreign substance that sit above the plane of the ground faces of the abrasive. You are really just reestablishing that same flat surface that was originally ground into them when they were made.

    And when you rub them across a metal table, the same thing happens. They only remove things that stick above the flat surface of that table. Once that has been done, no matter how hard you rub, they do not remove anything more. They only restore the original flat surface of the table.

    And in use, there is little difference between a 100 grit and a 400 grit precision ground flat stone. My pair have coarse and fine sides and there is no clear difference in how they act on a flat surface or when they are rubbed together. Even when I rub the coarse side of one with the fine side of the other there is little difference between that and rubbing the same sides together. They aren't just sidewalk flat. They are ground flat.

    I have come to realize that you should NOT stone a flat table or any other surface that is supposed to be flat with an ordinary stone, even one that has been flattened with ordinary means. You should only stone a flat table with precision ground flat stones. The other side of this is that precision ground flat stones are not to be used to flatten a surface. They are only a final, finishing touch to a surface that is already flat. That is the way it is in my shop and I am sticking to it.
    I wish you'd have told me not to stone tables with anything other than the dogs bollock precision ground flat stones 50 years ago. It would have saved me and my workmates a lot of effort over the years. I didn't notice the tables complaining at the time but maybe I wasn't paying attention.

    Regards Tyrone.

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    Quote Originally Posted by eKretz View Post
    You have part of this wrong. Flattening a hone on a diamond plate does the EXACT SAME THING as the diamond grinding wheel. In your mind diamond cuts the abrasive particles of the hone when it's bound in a grinding wheel but not when it's on a diamond plate? Not sure how you arrived at that conclusion... But having personally used both methods to flatten hones, they work out the same. The diamond plate knocks the abrasive particles flat just the same as the diamond grinding wheel. This is effectively glazing the hone. And yes it does make it act as though it were a finer hone.
    Thats pretty much my take on it, although watching Robins video (the mans at the bleeding edge of precision imo) id like to investigate if the motivation ever strikes.

    Its so subjective though, I mean the OP was talking a mill table, whats the global spec off the line on that? A few thou perhaps!? Ive got .020" plus on my 1970ish Abene for sure so what tool do you need for what job?
    I bet 99.9% o folk arnt truly concerned with a few millionths over a couple inch unless youre fussing over a gauge something or other, the law of diminishing returns applies.

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    The key when using a diamond plate is to use one fine enough that the diamond grit particles are a good bit smaller than the abrasive particles in the hone. If you use a very coarse diamond plate relative to the grit of the hone then it's very possible that you can end up with dislodged abrasives from the hone rather than cut ones. Then it will cut fast and freely rather than act as though glazed.

    There's another drawback to this also: even if the large diamond grit cuts the abrasive bound in the hone rather than dislodges it, it will likely leave (relatively) deep furrows plowed through the hone surface, which leaves a lot of projecting (easy to knock loose) particles that once broken loose act just like loose grit lapping compound on your part or machine table. So don't use too coarse a diamond plate if you want good results.

    Signed, a honing/sharpening/abrasives nerd. (With way too many hours of experimentation. Seriously, you don't even want to know...)

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    OK, thanks for that. I continue to learn. If I did arrive at that conclusion, I guess it was probably because I have never heard of manually making precision flat stones by hand. Perhaps that is because of the overall flatness that is obtained with a surface grinder but would be hard to get with manual methods.

    I will have to experiment with a stone and a diamond plate. I do not have a surface grinder; Yet.



    Quote Originally Posted by eKretz View Post
    You have part of this wrong. Flattening a hone on a diamond plate does the EXACT SAME THING as the diamond grinding wheel. In your mind diamond cuts the abrasive particles of the hone when it's bound in a grinding wheel but not when it's on a diamond plate? Not sure how you arrived at that conclusion... But having personally used both methods to flatten hones, they work out the same. The diamond plate knocks the abrasive particles flat just the same as the diamond grinding wheel. This is effectively glazing the hone. And yes it does make it act as though it were a finer hone.

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    OK, so I do not have a surface grinder and have not had the privilege and joy of ever having used one. But I have observed that many of the times that they are used, a fairly coarse wheel is used; like 100 or 150 grit. And apparently a fairly good surface finish is obtained with these wheels.

    On the other hand, I have tried and can not produce a finish that nice with manual methods, using 100 or 150 grit stones or sandpaper.

    I have also noticed that I can get a much finer finish on a part or tool when I use a 100 grit belt on a belt sander. And an even better finish if I use some oil or cutting fluid with that belt sander. I always attributed this to the speed with which the abrasive belt was moving. When abrasive is used by hand, the relative speed is low and only a few grains will act on a given point on the metal. But the powered belt sander moves the belt much faster and many more grains of abrasive will come in contact with that same small area. So the faster relative motion produces a better surface.

    And if oil or cutting fluid is used, then the loose abrasive will tend to stick between the grains of abrasive that are still bond to the belt, filling in the gaps. That lessens the cutting action of those bound grains as well as bringing the smaller grains of loose abrasive into action.

    At least that is how I have seen it. The speed of the belt is a factor and the finer grains caught between the larger ones are also a factor. A dry 100 grit abrasive used by hand dry and at low speeds produces a somewhat coarse finish. But that same 100 grit when running faster and with finer grains between it's larger ones can produce an almost mirror finish.

    I have observed this. Am I wrong? If so, where? Is there some other mechanism at work here?


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