A4 Alignment Fixer for ACCO Mutual 450 3-Hole Punch

This is a simple 3D-printed add-on designed to lock the metal paper alignment guide on the ACCO Mutual 450 3-hole punch in the perfect position for A4 paper. On vintage models, the guide is adjustable for sizes like letter and legal, but A4 often falls awkwardly between those presets. This adapter holds the guide securely in place, making it easy to get consistent and accurate hole placement that lines up perfectly with 3-ring binders. While this adapter isn’t 100% perfect, it gets the job done, with accuracy likely within 0.5 mm—which is more than enough for most uses. It’s easy to install, requires no tools, and doesn’t permanently modify your punch. It may also fit Swingline 74440/74450 models, although those likely already include an A4 paper position.

Update:
I’ve noticed that ACCO Mutual 450 punches can vary slightly in dimensions, which might affect how well this model fits. To help address this, I’ve also created a narrower version of the adapter that should fit most punches, though it may not provide a perfect fit. Additionally, here’s the Tinkercad link for this model so you can easily adjust it to match your specific punch.