Love the idea of E/G homebuild but I can only see one method I'm going to get flat surfaces for my THK rails. The self-leveling Epoxy method does not yield a flat surface by any means. At least not the Epoxy I have tried here in Oz.
The way I'm considering casting the rail surfaces is against a Granite surface plate (protected by thin Mylar) using inserts. See pic for general arrangement
I can only think of using some wax/hot glue to temp seal the thread from Epoxy.
This will be rather laborious and maybe risky.
Only other way is to have similar arrangement with long steel rails but I cannot machine 840mm rails. I may need to do a RFQ to see if it's worth doing.
Anyone tried a similar approach, ideas/comments?