If you are talking about enlarging an existing hole, it will work fine.
You may have to make multiple passes, re-setting the bit after each
pass. You will have to measure very carefully on the last few passes
if you need any real accuracy. All of which will take time.

The boring head, of course, will be a lot faster as you will just crank
out the slide after each pass.

If you don't have the central hole to start with, it's a lot more
difficult. You could grind up a trepanning cutter for a fly cutter
head, but it would be a lot of work to get the edges right for both
inside and outside cutting and it would only work for very thin stuff.
In the boring head you can hold the bit end on to the work, and can
therefore grind it a lot more effectively.

All of which is to say that you can often make do with what you have,
but that it won't necessarily be easy.

John Martin