The pin I cut from Joan's old Spark (842) did indeed fit exactly in the mast ball on Kevin Dutch's 1938 so it looks like they stayed the same.
The pin is 14mm high in the centre and 13mm high around the circumference (i.e a 1mm dome on the top)
The bottom 7mm of the pin is 12.5mm in diameter and the next 6mm is 12.6mm in diameter.
This gives a small shoulder around the circumference 7mm up from the bottom.
The hole in the alloy ball is drilled not reamed - no flat bottom in the hole. The hole is 12.5mm in diameter.
There was no glue in either ball and thus it appears that the larger diameter top 6mm of the pin is to make it an interference fit in the ball.
If your pin goes missing and you do not notice for a while the effect of the mast foot plate fixing rivits is to gouge away the top of the ball AND effectively peen the edges of the hole over - I had to cut this lip away.
In the very few weeks that Kevin's pin could have been missing his few sails in F6/F7 conditions had led to about 3mm of the top of the ball wearing away.
Hope the measurements may be of use in the future.
Steve
