How flat is a granite worktop?

[Tenson]

Update!

I got 30mm thick quartz, 1m x 0.6m and 2m x 0.6m

I created a steel support frame with screws around the top that I can adjust to support the quartz nicely.



I got myself a nice straight edge and I'm glad I did!

So far I only mounted the 1m piece, but the results are that it is pretty flat on the longer axis but cupped on the shorter axis. Damn, it's almost 1mm!

I expect it was flat when created as it comes in a far larger sheet, but I'm not sure if this cupping is due to storage or internal stress released when cut. Being cast, I expect the former.





Now I'm wondering how much I can help the situation by supporting it only at the middle points and clamping down on the outside edges. It has helped flatten it while the clamps are there.

I know quartz can sag if not well supported, but I don't know how long this might take?? Days, months? Any ideas?

[JAZZCNC]

If that slab is only supported at the outer edges I would be very careful what you put on the top as it won't take much of a knock for it to crack.!

[Tenson]

If that slab is only supported at the outer edges I would be very careful what you put on the top as it won't take much of a knock for it to crack.!

Its supported around the perimeter, but inset about 10cm.

[phill05]

Its supported around the perimeter, but inset about 10cm.

No where near mate,you need to fully support it no matter what you will use on it.

Phill

[JAZZCNC]

Its supported around the perimeter, but inset about 10cm.

I asked my mate who makes counters from Granite and quartz about using quartz unsupported and said wouldn't recommend it, just one tap in right place and it could shatter like glass. Apparently, it can crack under its own weight if wide enough and not supported well enough.