messin with my horn...what is this nut for?

[05crewcab]

I am having problems with the contact disk for my horn touching my turn signal lever...seems like the disk slides on to the column shaft too far. on the shaft below the disk is this nut in the picture. what does this nut do?? if I unscrew it up a ways the contact disk stays off the turn signal lever, but I think the nut is to hold the bearing down, so it should be tight right?

'72 tilt column and a grant steering wheel

any help with pics and parts needed to get the horn working would be helpful...I feel like i might be missing a washer or something to that effect. Thanks.