I did the same thing for my harbor freight tire changer, but mine is outdoors on the slab under a car port, which is exposed to rain and snow, and salt from my car. I used 1/2-13 bolts that I machined the hex down a bit to reduce the trip hazard, and innertube rubber washer gasket as a seal to keep water out under a steel washer. I also stuck lots of grease to displace any water that does leak in. So far this has worked to prevent the bolts from corroding in place.
I don't have a 3D printer, but I like this solution, that has a much lower profile, and grease should not dissolve the plastic.