would you

make a filet knife out of a wood saw that is about 50 yrs old the wooden handle broke and it was my grandfathers.would that be good enough steel to hold a good edge

I would think that modern steel properly tempered would be better. Just because it is old doesn't mean it's better. I had an old saw blade knife of my uncles and it didn't hold an edge.

Hard to tell. I have a couple of ancient saws that do very well as saws; hard to tell about a knife. But, no reason not to try.

I'd give it a try.