I noticed that my rotor seems to have a bit of play in it and can move back and forth. The spindle screw is all the way in. Is it possible that the bearing plate is not completely in it's place?

Could just be worn, too.

How old is the horn? What brand/type of valve? Is the bearing plate(s) fully seated?

The spindle screw just holds the linkage to the rotor stem. if it's moving back and forth, it's either worn, or the backing plate could be not installed correctly.

[quote="hornbuilder"]How old is the horn? What brand/type of valve? Is the bearing plate(s) fully seated?[/quote]

It's an ancient yamaha

Some years ago I had a Holton TR181 with worn rotors giving some lengthwise movement. My solution was to get my tech friend to drill a very small hole (about 2mm diameter) in the centre of the removeable valve cap and tap the hole to take a "needle screw". This is a hardened steel screw with a fine needle point on one end and a screw head slot or hex head at the other. The needle point then went into a countersunk depression in the end of the rotor spindle where it sits in the bearing back plate.

The valve is re-assembled and the needle screw tightened until it comes into contact with the countersunk depression. Then unscrew the needle screw by no more than half a turn and check the play on the valve. It can be adjusted either way until the valve spins freely but has no longitudinal play.

I still play that trombone and it has never needed any adjustment in 10+ years, just lubrication.

I am not sure how this would work on tapered rotor valves-I think mine on the Holton are cylindrical.

Cheers

Stewbones43

Yamaha have a movable bearing on the spindle side bearing plate. Have a tech adjust the position to remove the end play.