Reduce 8mm square tube to 7mm square tube without pro metal tools?

Old swedish windows have 7mm square tubes for handles. All handles of the design I want are 8mm so I want to make them smaller.

I have access to a carpentry with very good tools for woodworking, (including mill press) and some basic stuff for metal, like an angle grinder.

It’s 11 handles, and the result doesn’t have to look nice as long as it works since the square tube is inside the handle.

Is there any good way to get rid of .5mm of the square rod at the end (only like last 10mm or so) on the handle.