Gallery, Projects and General > How do I??

Is it possible to make a poor man's flat stones with a glass plate?

<< < (2/4) > >>

JHovel:
My understanding is that this approach would not work.
If I have it right, the idea is to grind off all the sharp points of the abrasive grains on the face of the stones. That way they will no longer remove metal by 'stoning' or abrasion.
However, the edges of the now ground flat grains are now sharp. The gaps between the grains are now crucial to the flat stones' function: anything sticking up from an otherwise flat surface will 'fall' or protrude into the gaps and will get sheared off by the edges of the grains.
To make use of this property, the stones need to ALSO be dead flat.
To achieve both at the same time, a surface grinder is used with a fairly fine diamond grinding wheel. It needs to be fine so as not to rip out any grains, but grind them down.
I've done that as an experiment with a few low-cost bench stones. I found the bonding resin or medium of the stones needs to pretty tough. Many stones have their grains bound by fairly soft and weak bonding. I guess that's a good idea if you want to expose new and sharp grains for stoning things. For this purpose, that's the exact opposite of the properties we want for flat stones.
A couple of very cheap stones I found in local hardware stores had very hard bonding and sure enough, they were crap at sharpening tools. Even using their coarse sides, they would quickly stop removing metal and just polish or burnish metal.
Once I ground them on the surface grinder, they behaved perfectly as flat stones.
I've made a few pairs of them for friends and myself now. They do exactly what Robin described and demonstrated in his YouTube videos.
Cheers,
Joe

nrml:
If I my understanding of what you are saying is correct; if I went ahead with my plan, I might end up with 'flat stones' but the grain size would still be too big for it to work as a precision flat stone as the lapping process would only remove the binding matrix  and not shear the abrasive particles on the surface to a finer grain size.

That does make a lot of sense. Thank you for the information. I am glad I asked the question before jumping in feet first and wasting time and money like I usually do.

sparky961:
It's been a while since I watched Mr. Renzetti's video on this, but I recall that he used the stone on something that was previously surface ground, and it highlighted how poorly that item was ground.  I've done the same using the method I detailed above to the stone, then taking the stone to a 1-2-3 block that didn't cost me much.  Sure enough, the previously unseen wavy surface texture was highlighted across the entire surface.  This may not prove definitively that my stone is flat, but I'm sure it's a lot flatter than when I bought it.

I suppose one could set up a test so that the surface of the stone is parallel with a known-flat surface plate.  Next you'd run an indicator of appropriate resolution over the surface to check flatness.  Now, I don't know about you, but I'd rather not grind down the ball on my nice Mitutoyo 10th's indicator.... but to each their own.

nrml:
I don't think getting it flat will be an issue. Just the aggressive abrasive action of a hand lapped stone versus a much milder polishing action from a diamond ground stone would render it far less useful for finished surfaces.

vtsteam:
This seems to be one of those long technically jargonized weigh-ins involving multiple statements of personal imagination that could more easily resolve itself in real life by just trying the experiment.

It will work or it won't. The answer will be evident in an hour.  :dremel:

Navigation

[0] Message Index

[#] Next page

[*] Previous page