Just thought of another irritant regarding the TE 20 Ferguson tractors. The one on the farm at home bought new by my Dad did an awful lot of rowcrop work - potatoes, cabbage/cauliflowers, lettuce and the like. So we often had to change the track settings. The front was easy but the rear involved undoing the 6 bolts that held the wheel rim to the wheel centre. These were about 6 inches long and had a fine thread. The bolts had a dome head with a small lug on the inner side to grip into a notch in the wheel rim.
The fine threads could get horrendously tight due to exposure to water, mud and manure. Whilst it was often possible to get them undone about 3 threads, once that little lug could come out of the notch it was exceedingly difficult to get a grip of the dome head, particularly with certain wheel settings where it became very recessed between the rim and the wheel centre. Eventually we threw the lot away and fitted coarse thread bolts with a standard head and a strong spring washer. And despite our initial doubts they rarely ever came loose as had been our fear - the fine thread bolts were to overcome this potential problem.