[mcphill]

What method do you plan to use to grind it flat, keepin the two surfaces planar? Please keep posting, we are all watching with great interest!

[petruscad]

What method do you plan to use to grind it flat, keepin the two surfaces planar? Please keep posting, we are all watching with great interest!

There are several techniques:

1. Standard surface plate method. Use a flat surface large enough to cover one side of the base. Cover the surface plate with Prussian blue, rub in on the base and then grind off the spots where it touches.
2. Fixed surface plate method. Support the surface plate on 3 points in the middle of the base. Move a surface gage on it with a dial indicator touching the base and progressively grind the high spots until the required precision is obtained.

Its important to realize that not the whole surface needs to ground to the same level of precision. Only the area where the rails will mount to needs to be ground to extreme straightness and planarity.

I will probably use both methods. I have a large surface edge, not as large as needed but large enough, which I can use. I also have a variety of smaller straight edges, machinist blocks, parallels, gage blocks, etc. I have the needed surface gages with thousands and ten-thousands indicators.

For grinding I will use a 6" coarse diamond coated lapidary disk as well as smaller diamond plates, disks etc, to do rough, global grinding as well as local, fine grinding.

[castinite]

The epoxy is not the big problem. The aggregate dust, if it has quartz in it can cause silicosis. Always wear a mask approved for the dust that might occur.