Safety Box Opener (Utility Knife)

afety Box Opener (Uses Utility Knife Blade)

This uses the standard blades that are suitable for most Utility knives…. so the chances are you already have the hardware required for this print.

This is a second variant of this model. The first used Bambu Scrapper blades and mounting screws which can be found here. 

That model was born out of frustration with other already available options & I really wanted a truly ‘fit for purpose’ tool to open parcels & boxes with. Too often I would just grab a pair of scissors and use with the blades opened (and grasped in hand!)… so safety was also a key consideration here.

I am grateful for the extremely positive reception that model received & to all the people who requested that I make a version that would accept standard utility knife blades….well….this is that model & aims to solve the same problem; opening those pesky taped up boxes!!!….. but this time (to keep things fun), I have implemented a new spring trigger return technique……

Key Features:

• Blade always returns inside the handle courtesy of a printed ‘flexure’ trigger return spring. This time its based on a torsion spring principle and works extremely well! So still no need for a metal one (tested many versions to get one that won't deform… even when using PLA).
• That said, I have still included an optional location for a metal spring from a pen (aprx. 4mm Diam. x 22-25mm Long) should you wish to use instead.
• Handle cover plates simply snap fit into place, and can be removed (if needed) using the flat screwdriver slots provided around the perimeter.
• A hole at the tail end to enable you to hook onto whatever you like :)
• All items print with zero support, and no additional hardware is needed other than the knife blade.

Makes for very satisfying assembly and use!!! Will also fit on any BambuLab printer including the A1 Mini… enjoy :)

Assembly:

1. Add the Torsion spring onto right hand cover plate by aligning the small ‘dot’ on the front face with the same on the hexagonal pillar on the cover plate.  ***Please note: orientation of the spring….. if you have aligned the dots correctly the leg of the spring will sit against the bottom edge of the cover plate where the trigger will be installed later. You now need to pretension the spring by gently lifting its protruding leg up and over the edge of the cover so that it sits against the top edge (pressing downwards)***

2. Insert the Blade into the knife retainer - trigger with its tapered edge dropping into the groove first and then you can let it fall back into place. It should sit over the locating peg (which must go in the rightmost blade slot).
3. Attach the knife retainer - cap by installing it onto the top of the blade and pushing its peg into the left slot of the blade & the corresponding hole in the trigger. This may be a press fit so make sure its pushed all the way home, and don't worry if its a loose fit either as it will be held in place by the cover plate later on.
4. Insert the above Knife trigger assembly into the right hand cover plate by locating against the corresponding ridge within the cover plate (the one that matches the its upper edge profile). Be careful to also place the rightmost (pointed end) of the trigger handle up against the back edge of the torsion spring leg.

5. Attach the left hand cover plate, which should index together (sandwiching the knife blade assembly) and then snap fit into place around the permitter.

   ***See also the animated GIF (above) & exploded assembly BOM below***