All depends on WHERE ..... "Location: FL,USA"
How close to a sink hole are you??
and just for your info, 4 inches is barely a driveway, for a little car....
use a proper slab min 6 inches reinforced...8 is better..
"....for our info" Gary? That's absurd, for all the reasons above and more. You must have missed John's 14,700 pound jig bore above!
As for
"use a proper slab min 6 inches reinforced...8 is better." with that "logic", why not 18" with 24" being better?
Useful advise is being sought here.
MBG, unless the slab is already showing signs of failure, I wouldn't hesitate to bring that machine in. Let's suppose that you are unlucky and the 4" slab doesn't easily hold it, what better test?
Won't go to China.... push the machine out of the way and cut a hole in the floor, excavate, compact a 12" layer 3/4" CRB (crusher-run-base), pour a 6"* reinforced slab and let it cure for a month. But fer crimminy sakes, don't go to all that
silliness unless the need is proven, which is
highly unlikely!
*6" because that will still be below the minimum ready mix delivery charge and you'll be adding useful anti-vibration mass. With that kind of prep, 4", 4,000 PSI, reinforced mud would be overkill for strength on that moderate load.
Don't dink around with "expansion joint"* between the old and new, too many people don't understand that. The new slab WILL SHRINK! Guarenteed. It can
never apply pressure to the hole in the long-ago-cured slab around it. You'll just make a hard to keep clean recess around your lathe. Do dowel them together, help the old slab to remain stable, that's "flush" to the new.
*Do use expansion joint around an existing slab, before you pour
around it.
Oh yeah MBG, how do you get around
all those "sink holes" on the way to.. wherever?
Bob