Action stuck in piano

 Normally, the grand piano action slides out after removal of the board in front of the keys (the keyslip), the fall board (key cover), and the cheek blocks.  One has to check to be sure no pressure is being placed on the keys at the left and right edge of the row of keys, to avoid breaking off a hammer during removal of the action.  Although this happened to me on another antique grand, I repaired the broken hammer shank and subsequently sold that piano several years ago.  Nothing was visibly obstructing the sides, top or bottom of the action to prevent it sliding out, which leaves the bottom of the action.  You can picture trying to look underneath a drawer that is stuck to find out what is blocking it.  It was very difficult, but using a yardstick and a stiff piece of thin steel for probes (the latter about 18 inches by 8 inches in size), I did find 2 tight spots one of which was visible using a fiberoptic camera to view under the keyframe.  This was the shift lever, a piece of forged iron that pushes the keyboard to the right when the una corda pedal is depressed.  However, the true sticking point was not immediately visible, and consisted of mis-aligned boards (both on the bottom of the keyframe and the top of the keybed--see photographs).  By wedging the keyframe up about 1/4", I slid the piece of sheet metal near the center of the action, underneath, then was able to pull the action out.  I literally tried  100 times to remove the action, over a period of many months (intermittently), and it was a great relief to get the action out.  There is also a small plate under the keyframe which engages the shift lever which I had initially thought was crooked and the corner had dropped below the plane of the keyframe bottom.  However, on closer inspection, this was not the case, or the reason for the stuck piano action.  The plate has a loose screw which I will tighten after I remove the hammers and the keys from the keyframe so that I can turn it over.  As you can imagine, I am using the utmost care with this piano due to its age and fragile state. 

This is the shift lever.  I had to manipulate it slightly to get the keyboard out, but it was not the cause of the action being stuck as noted above.

This is the keybed cross board which has raised slightly from a flush position.  That corresponds to the following misaligned board on the keyframe, pictured below.

Malalignment of the underside board of the keyframe which forms a virtual dovetail with the misaligned board of the keybed, causing the action to stick at about 1/2" forward from the playing position of the action.