The plate is mostly called a blade holder or cutting disc.
We have discussed this in another post of yours.

You need to advise us of what you have done.
Have you procured a new washer and nut?
Have you tried to use them?

Previously, we said this holder was showing signs of wear.
We do not recommend anything but a professional-standard repair.

No welding, no incorrect parts.
If you are unsure, see the Victa Dealer in your area.

https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=62257#Post62257
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=62324#Post62324
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=62379#Post62379
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=62413#Post62413

Hope this helps.
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JACK.