Rivets are easy to remove if you need to, here's how:
Take a centre punch of hardened steel
(you wont have one I think, I have a few of different sizes)
(A big nail works OK too, just that nail bends after a few goes.)
(Nail prefereably considerably bigger than diameter of hole)
Place point of nail in hole on flat side of rivet (not the far side
where the rivet aluminium is distorted)
Whack nail with hammer, start gently, the centre steel bit flies
out the back, or gets lost in whatever container the frame is. No
problem if a static window frame, but if rivet is in a mobile box,
think if rattle will annoy after.
Drill out rivet: Use a drill only a fraction bigger than hole,
sufficient that drill bit should only abrade most of the rivet's
aluminium liner in the frame. not the frame itself, You dont even
need absolutely all of the width of a new rivet, because invitably
you will drill slightly off centre &/or skew, so you will take off
all aluminium one side of the cylinder, & it will fall out.
So dont wobble the drill bit, be very delicate if the frame is also
aluminium as well as the rivet, 'cos you can't feel boundary between
rivet & frame when drilling, & dead easy to drill too big & make a
wobbly a hole, so that next new rivet will not hold in.
The top of rivet gets stuck on drill shaft,, sometimes one stack
up several drilling out.
unplug drill, take wide jawed pair of pliers use the pliers'round
depression tp hold the aluminium rivet head, manually gently rotate
the rivet head off the drill bit, without snaping or blunting drill
I have 3 rivet guns,
1 magnifcent cantilever tool I used to repair window frames a few times
+ 2 smaller tools, easier to get the rivet head into tight corners,
but can hurt a bit when squeezing (yes it takes a hard grip to snap
a steel nail in a rivet, even with the long leverage.
1 of those 2 has a rotatable head.