Thank you for information will keep look thanks againWell, that's got me stumped. I wonder if it's had its headstock spindle changed in its previous life by earlier owner.
Maybe you could look to replace the spindle shaft with a more common size, 1" 8tpi or 3/4 16tpi?
Sorry, but can't think of or find any other solution, short of buying a plain bore to 1" 8tpi or what yo prefer and get a machinist to tap the bore to suit your existing spindle thread.
Like this possibly: