I recently inherited a pair of Type 19 Stanley smoothers. The no. 4 works like an absolute dream after total overhaul and with Hock blade/breaker. The No. 3 is a different story. The frog was dressed/moderately lapped just as as I had done with the No. 4  – but no matter how loose the lever cap was set – as soon as lever was pushed down the adjustment nut became really tight needing two fingers and quite a bit of pressure to rotate. The nut on the No. 4 by contrast operates easily with one finger and moderate pressure from lever cap? I checked the trough in the adjustment nut that the yoke tips ride in  – and noticed there was some grinding away of the brass nut. So I then lightly filed/dressed burrs that were on the yoke tips and very lightly sanding away grind marks from the trough. Added teflon lube to all surfaces including frog surface and result still the same. Note that the nut freely and easily on threaded rod with lever cap unengaged. Any thoughts about what the “culprit” might be here? Thanks in advance for any help.