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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.
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??
You use a 150 grit stone on gage blocks??
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.
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).
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.
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.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.
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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