screw size for vintage saarinen elliptical table?  

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Take it to a hardware store they will tell you.

as you might expect, it's...
as you might expect, it's kind of hard to take a giant table top that weights several hundred lbs to a hardware store...

are they screws or bolts?
are they screws or bolts?

Knoll is still in business
Call them!
Cheers.

eehhh, but hardware is...
eehhh, but hardware is tricky business...especially since its a vintage piece...they may have changed size/thread pitch/type all together...then one piece of misinformation and you got a very heavy very wobbly table because you stripped it out......
No Pressure ;}

Rule #1:
Don't ever force a piece of hardware; determine instead why it isn't working.

honestly....
it may not be the most efficient way, but i would procure{buy/garage dig} a wide variety or bolts/screws {metric&standard}and test to see which fit....gentle hand tightening only...no tools necessary....whichever feels like the snuggest fit without any force is the winner....sounds "shade tree", but unless you have a set of thread pitch gauges...