I have now started pushing the back plates through the thickness sander. Had a major accident with the sander today. I forgot to fix tight the drill that turns the sanding drum. The drum stopped and the drill started spinning, it bent the drum axle about 70 degrees before the torque control triggered and shut the drill down. I don’t have a spare 8mm steel rod to replace the axle but I managed to take the axle out and refit it from the opposite direction. The shaft must have been slightly bent anyway because it always had a slight vibration on it before and now it runs really well with no vibration at all.
I am currently using a 40 grit sand paper to reduce the backs down to about 2mm. Here are the two backs after having the first run through the sander.
They are currently 5.6mm thick so I have a lot of wood to sand away.