I followed a procedure I got from the 7x12 forum, briefly put a round bar in a chuck (3 jaw is ok) clock it near the chuck rotating the lathe by hand, average the difference between the high and low readings, move well down the bar and do it again adjust the packing until the results are the same. The bar has to be straight and the same diameter for this particular version of their procedure to work.
Initial I was about 0.15mm out at the chuck and 8 inches down the bar about 0.27 out, I spent about 11/2 hours adjusting the packing and retesting each time and I came out almost exactly as I went in almost no change!!
I know the lathe is past it's best
I'm confident that a skilled and experienced engineer could sort it out, there is some wear in bed it's looser near the chuck, the tail stock can move from side to side slightly + so does not always clamp centrally , there is some damage to the tool slide and the bearing clamp behind the chuck has been welded, it must have snapped at some time, but it adjusts now.
If somebody could explain (simply casuse I'm new) what went wrong and how I should proceed I would be greatfull.
Many Thanks Alan