Ran into an issue with TCSS parts and searching the forums didn't help. I purchased a 1" Thick walled Polycarbonate tube and an MHSV1 Blade Holder Style 1 blade holder. They aren't fitting together even though they measure 1" with the tape measure so some sanding is in order. I should sand down the Tube instead of the blade holder, correct?

All I have for sanding is an old wood file so do I need to get some sandpaper for this? If so what kind?

Thanks.