Granite surface plate.

[Aust12]

Hi, I’m still in the design phase of building a small cnc mill.
I was thinking oh getting two 600X400X100 granite surface plates
And bolting them 90deg to each other as the bad of the mill.
Has anyone tried this method,
My worry about the plates is that the Z axis plate might break
Or shatter with the force of the spindle and also the overhang
Of the spindle. The plates will be the cheap version and are about
300euro each.

[Robin Hewitt]

Why not buy a mill and bolt some motors on it?

[JohnHaine]

A few years back there were some articles about adding rigidity and mass to the small X1 mill by filling the hollow square column and also the base casting with epoxy concrete. Using an existing structure gives you a good starting point. You could also use standard aluminium or steel sections and fill those with epoxy-concrete, I believe this approach is used in industrial machines.

I think using lumps of granite will be fraught with problems - they are only finished flat on one face I guess so you couldn't rely on the edges being square or parallel. They are heavy to handle, hard to drill, and not strong in tension.

[mekanik]

There was a post on the forum showing a build of an epoxy granite mill, the full article is over @ model engineer https://www.model-engineer.co.uk/search/default.asp?sch=epoxy%20granit%20mill&Refine=1
It is well worth the effort to try and find this as the construction method is spot on.
Regards Mike
PS try a search for laser levelling as well the gentleman (believe it's John from down under) also contributed to that thread
PS found it try searching John McNamara on the ME site

https://www.mycncuk.com/threads/12353-DIY-Epoxy-composite-gantry-frame-milling-machine