When to replace my xacto?

[Shiromisa]

I figured customs is the right place for this since I used my xacto knife mainly for customs, and thought others might too. How can I tell when it's too dull to keep using and must be replaced? I know dull knives are more dangerous since you need to use more force to cut.

[CarnationTwirl]

If you can still cut precisely through paper it's still sharp, but if it drags and pulls when you're trying to get a clean cut it's time for a new blade.  Mmm. Nothing feels as nice as a fresh blade.
So get some printer paper and do two horizontal and two vertical cuts that overlap so you have a square, if you lift the paper up and it basically falls right out, your blade is still sharp.  If you have to like tear/force it out, then the blade was too dull and it's time for a new one.
Or just err on the side of caution and use a fresh blade anyways, they're not terribly expensive.

[sd_dreamcrystal]

What CarnationTwirl suggested. Personally if my cuts are not that easy when I'm going through the plastic then I know it's time to replace the blade.. I go through more blades than most non-customizers do and I think almost any customizer does as well plastic wears the blades faster as far as I know

[archidraca]

I have a pet piece of foam core. If it chews up the inside, it's too dull.