I have a vintage Kity 636 planer/thicknesser and one of the lead screw nuts has become hopelessly jammed so that the thicknesses table is immovable. I have dismantled the table and had a go at picking the nut but I seemed to be doing more harm than good. The thread is single start and seems to be ACME, stub ACME or trapezoidal and has a lead of about 2.5 mm. The OD seems to be about 12.13 mm and the TPI aboiut 10. I can't get very accurate readings with my digital vernier so the measurements are not guaranteed. There are no spares available since the Kity outfit no longer exists and I can't find anybody who has Kity spares except for new belts, etc. I have sent the lead screw and nut to thread specialists in the hope that they can provide a tap which would clear the blockage. After a couple of weeks or longer, no results. It is just possible that spares ay be available in France sine Kity was a French company but haven't tried this avenue. Any suggestions would be welcome