How to shake a 100mm hole in a piece of steel.

This is me drilling the 100mm hole for the ISO flange for the top of the diff pump. Its a bit of a late post but I didn't have the pictures at the time.
The external measurement of my stainless pump barrel is 102mm. The hole saw was cutting a little too large. I think it wasn't exactly a circle. I've noticed this on other hole saws too.

I decided I'd bend the teeth in a little to give me a tighter fit. Well, you can't do that. I is a very brittle alloy. And I happily snapped off two teeth without too much pressure.

So plan B was to sand the outside of the saw to remove the outer edge of the teeth. Now that did work. Always remembering not to let the teeth get too hot or they will loose there edge very easily.
Here it is whizzing around. I set the pillar drill too its lowest speed. I predrilled the pilot hole too. I wanted to get as little wandering as possible. The whole drill press shook like hell for the first few minutes, until the groove developed.
Again, I stopped quite of the to oil the groove and make sure it was cutting freely. I went all the way through from one side this time. The clamping of the disk was a pain and I didn't think I could line it up again from the other side.
It worked out just fine. In fact, it was bang on. A friction fit onto the tube without any sanding.
That doesn't happen very often...