According to x@y:

If you *must* do it this way, consider renting a hole saw the right
size.

When I hear "hole saw", I think of an accessory that attaches to a
hand drill and that's most often used to drill new wood doors to
accept locksets. Is the hole saw you refer to similar to this or do
you refer to a specialized tool that's dedicated to hole cutting?

That's basically the right tool, however, the ones they're referring
to are much beefier than the cheapies sold with lockset kits. Usually
carbide tips etc.

You will need a _big_ 1/2" drill to do this. And very strong arms.

For a friend, I drilled a 2 1/2" hole in some well casing to install a pitless
adapter.

It was an industrial rated hole saw attachment on a heavy duty 1/2" drill
(one of those really old 600RPM monstrosities with "jack hammer"-like handles).

Little risk of shattering the pipe (it's steel, not cast iron), but, I
broke about four 1/4" pilot bits [+] and knocked off a couple of carbide
teeth. I came close to losing a few teeth of my own.

Install a proper Tee like everyone else suggests is the right approach.
You won't be happy with the saddle connection. Even if it were legal.

Saddle connectors suck. They ALWAYS leak.

[+] Today's helpful hint: in thick metal (especially pipe), predrill the
pilot hole for a hole saw. Then, substitute in a suitably sized hex screwdriver
bit into the hole saw, and use _that_ to guide the hole saw. Standard hex
screwdriver bits are _vastly_ better able to stand up to chatter than a 1/4"
drill bit. How did I learn this? By running out of 1/4" drill bits and
being a bit desperate...
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.