Could somebody help me how to calculate torque applied for parallel stack of Belleville washers at working load.

I am trying to use following Belleville Washers.

.380" ID, .750" OD, .056" Thick
Deflection @ working load = .007/Working Load = 430 lbs/Flat load = 845 lbs.

I would like to set 3 of these as parallel stack so that deflection remains same but load multiplies.

How to calculate toque applied for a working load of 1290 lbs (3 X 340 = 1290)??

thank you so much,