G'day Rowa45 & Norm,
If what I circled in the below pic is a washer you may need to drill the washer so you can get a bolt into the crank,
sometimes the washer gets distorted and gets a thread on the inside of the washer because it's tight on the
crank bolt. As Norm said the common crank thread is 3/8 UNF.
You shouldn't need 6 ton to remove a crank hub as I just use a little tension on the puller then shock the hub off.
Click on this link that tells you how to remove the blade
https://www.outdoorking-forum.com.au/forum/ubbthreads.php/topics/120280.htmlCheers
Max