Gallery, Projects and General > How do I??

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

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nrml:
After watching Mr Renzetti's video I am convinced that a pair of flat stones would be a handy thing to have around the home shop. Unfortunately I don't have a surface grinder or the money to buy a pair of ready made stones.

This got me thinking. If I get a float glass plate like this https://woodworkersworkshop.co.uk/products/scary-sharpening-glass-plate?variant=9040138371 and fix a sheet of abrasive paper onto it with spray glue and lap two Norton stones with it using the three plate method, what are my chances of getting a half decent pair of flat stones? I am thinking that lapping the two stones against the float glass first would save a lot of time and effort compared to attempting it directly with just 3 stones. I can lay the glass on top of my little Chinese granite surface plate to reduce flex. I don't really want to apply abrasives directly on my little surface plate as it is the only one I've got.

I'd be very grateful if someone would point out why this would be a waste of time before I find out the hard way.

sparky961:
I've done this "by hand" using an inexpensive diamond file (the kind with the plastic backing and oval holes), a surface plate, and a pencil.  You use the surface plate with some fine paper as the reference.  The pencil serves as your "bluing".

Start off by marking a crosshatch pattern in pencil on the entire face of the stone.  Rub it on the fine paper on top of the surface plate (doesn't take much) to determine the high spots.  You can take the pencil and draw circles and such around the high spots to make them stand out more.  Then take your diamond file and work down ONLY the high spots.  Don't get carried away.  After the diamond file, go and rinse the entire stone with water and maybe some soap.  Keep repeating the process like you would for scraping until the high spots are dispersed and small.

When you get really close, just rub the stone directly on the surface plate.  This should make the graphite (pencil) shiny where the high spots are).  If you have the patience, you'll figure out a system that works for you.

vtsteam:
Well first of all I never think an experiment like this is a "waste of time" even if it doesn't work out as I hoped. You always learn something interesting in the process.

Second, seems to me, and maybe only me, logical that the three plate method assumes three plates with similar wear characteristics.

Having two of them different to the third seems to me likely to defeat the entire reason it works. But what do I know?

People, like myself, who have never tried what they propose as "true"  (at least in this case) are just as likely to be wrong as right! :coffee: 

:beer:

nrml:
I have been ruminating over this for a few days and my initial thoughts were that  the difference in wear characteristics between the glass/sandpaper and the stone  would completely mess things up when swapping around three-ways. However, my research seems to suggest that float glass is usually exceptionally flat - often exceeding the flatness of budget surface plates. Where it loses out is in flex due to limited thickness and lack of calibration. It wouldn't be guaranteed to be reliable for measuring but for sanding / lapping it should be flat enough.

If I flatten out both stones as much as I can with reference to the the plate as suggested by sparky961 I should be almost there. As a final step if I lap the two pre-flattened stones against each other, flip and repeat, I should in theory get them to match quite closely.

The potential unevenness of the paper and glue layer is what is casting doubts in my mind about the practicality of this approach. Also, I am not an engineer or machinist, so I might be overlooking something elementary.

I'll give it a go over the next few weeks and report back.

vtsteam:
You never know until you try......  :beer:

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