[Vwdiesel] Homebrew Surface Plate

[Jim Arnott]

Best surface plate I ever came across was when I was buying  a large 
custom machine base for an aerospace company I was working for.  Out in 
Pyramid's (http://www.pyramidgranite.com/) yard they had a broken 10x6 
lab grade black granite plate (AA)* that had been dropped.  Got them to 
saw me a piece of it for $20. Ended up with a 18x24x8 inch Imperial 
granite surface plate that is for all intents and purposes dead flat. 
(well... it's flat within seventy millionths.)

If you *really* want a surface plate, you might see your local monument 
maker.

If you're going to be lapping things, glass is good.  A surface plate 
should NEVER have an abrasive applied to it.  NEVER!  It'll wear holes 
in it and it won't be flat anymore. No matter what the material.

Here's a good article on surface plates: 
<http://www.qualitydigest.com/aug03/articles/03_article.shtml>


*   Laboratory grade AA: (40 + diagonal [in inches] of surface plate 
squared/25) x 0.000001 in.

Jim

On Tuesday, May 11, 2004, at 12:50 US/Pacific, jwkeith wrote:

> "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.