JourneySorry those aren't working out for you. We've heard mixed reports on this, and I suspect it's because X-acto blades are mass-produced and often knocked-off, so the real deal doesn't fit but some copycats do. The stock blades that are installed when they ship and we recommend for replacement are the most commonly available on Amazon, here's a link: https://www.amazon.com/Techni-Edge-TE01-111-Hobby-Blades/dp/B0006GBSXG