HORN sounding when turning the wheel

[PARKIE007]

I have recently had a new feature on my 1968 Jaguar 340 in that the horn started sounding when I turned the steering wheel hard whilst manoeuvring. After much research and fiddling about I found that the bottom of the inner steering column was moving within the outer column and earthing against it. I have resolved this by wrapping insulation around the bottom few inches of the inner column. However, can someone please tell me how far the splines on the upper column must go into those on the lower column, and how tight must I do up the pinch bolt? Currently the lower part of the splines are fully engaged and the upper section is about 50% engaged. The pinch bolt is very tight but there is still a gap of about 3mm between the metal arms it is 'pinching'.