Since you already have rigid body constraints there, you can just try adding beam element nodes to rigid body constraint node sets. Then you won’t need *EQUATION:
test_bolt 2.pmx (779.3 KB)
I also changed the beam profile to rectangular so that two-node beam element (B31) can be used.
If you want to use a different approach, the recommended way is to use *EQUATION with distributing coupling constraints: Modeling bolt connection with preloaded beam element - #5 by FEAnalyst