[Vwdiesel] Homebrew Surface Plate

[jwkeith]

"Home Shop Machinist Magazine" recommends the following as a "homebrew surface plate"

Get a piece of plate glass.  This is the kind of glass frequently seen on the tops of fine furniture.  Your local glass place probably sells this kind of glass but you want it as thick as you can buy/steal/borrow it.  The glass doesn't necessarily have to be square or even rectangular.  A corner busted out of a rectangle or square only limits your use by a few square inches. 

Make a box out of wood perhaps two inches deep and a little larger than the piece of glass.  Then fill this box with plaster of paris.  As the plaster of paris starts to set, it heats and assume a slightly "resilient" texture.  You'll know when you've reached this point.  

At this point "float" the glass on top of the plaster of paris and give it a couple of "taps" to bring water to the surface of the plaster of paris and make the glass sink into the plaster a little.  .  

Then leave it all to set.  

When you're done you'll have a surface that is probably flat within 0.0001 over the entire surface.  Of course there is no proof of this unless you decide to make three surface plates by this method and then grind them all in against each other. 

Best,
Joe