Hobby project

[albertq]

Not sure how you plan to bolt the vertical tube frame to the horizontal tube frame, but I would add two plates at the bottom of vertical frame as "T" to allow for the torque applied when shaping a tall piece of metal. Also leave sufficient grinding wheel clearance below vertical axis granite to dress the wheel substantially smaller.
I have no doubt you have thought of all this already.

[tonyfoale]

Not sure how you plan to bolt the vertical tube frame to the horizontal tube frame, but I would add two plates at the bottom of vertical frame as "T" to allow for the torque applied when shaping a tall piece of metal. Also leave sufficient grinding wheel clearance below vertical axis granite to dress the wheel substantially smaller.
I have no doubt you have thought of all this already.

Better than the plates is the planned bracing on the metal version. I rotated the pic. to avoid confusion as to which are the horizontal beams.

Click for full size.

[tonyfoale]

I have had messages suggesting that the bottom rails were too close together. They are not, they are spaced optimally. Consider the sketch.

End view.

Granite is a brittle material and in common with some other materials such as concrete etc. is best not used in tension or bending. My designed spacing uses the granite plate to provide damping and is stressed basically in compression as a spacer. It is not really structural. I do nothing by accident.

The Z and Y axes (in mill config) will have the rails spaced much farther apart, as will become apparent in a future post the other two plates will be also used mainly as spacers providing mass and damping.

[tonyfoale]

I have made a new post for part 2 of this project, you can find it here My Surface Grinder. Hobby project Part 2

The X axis is up and running, it lives.