The exact value may depend in the size of the waveguide, and the hardware used. Typical values might be on the order of 10 inch-pounds (note INCH-pounds, not foot-pounds). Some might be a bit lower, sime might be significantly higher.
If you're dealing with high power and/or pressurized waveguide, or sizes much smaller or larger than 'middle of the pack' X-band WR90, then you *really* need to track down the applicable spec for your system.
