This is a "remix" of sorts two models from Thingiverse

Unfortunately, thing:2917912 was removed from Thingiverse for some unknown reason. I printed one of the originals when it was available and it recently broke. Finding the original model no longer available, but having this version to base my work from, i recreated the original

As with the other designs, this folding utility knife uses standard utility knife blades (commonly known as "Stanley Blades", at least here in the UK).

As i recreated the original design, all the holes take machine screws in M3 size. The attachment between the blade holder and the handle needs a M3 x 12 and to secure the blade itself, you want an M3 x 6. I personally use the "button head" style.

The only difference from the original design is the removal of a small internal flap which was designed to lock the blade from opening. In FFF 3d printers, this simply doesn't work as the plastic has no memory. To put it simply, with the blade closed for 24 hrs or-so, the plastic locking flap no longer springs to the required position when the knife is opened so the blade doesn't lock in the open position. It was a cool idea, just never worked in reality.

The knife uses a standard 3" carabiner.

I always have one in my desk drawer for a quick and easy to reach for knife, they're handy in the workshop and on your keys since the carabiner acts as a blade lock to keep the knife closed for safety so it cant just open up on your keys.

They can take quite a bit of pressure before breaking, but of course this is PLA, so they're not indestructible!

Post-Printing

The tolerances on this are reasonably tight, things like the hex-shaped slots for the nuts especially, you may need to work on these areas to get things to fit post-print.

The blade holder section can be a little stringy too, again, quickly run a blade through the channels and it clears up and the blade should fit in.