This is not tested, but it is derived from a working 120 adapter (just updated) (https://www.youmagine.com/designs/35mm-film-on-120-spool).  If you use this 620 adapter, please let me know of your results. This adapts 35mm film for use in 620 medium format cameras.  By using this, you get full exposure of the film strip, sprocket holes and all.  While this is designed to be a perfect copy of a 620 spool when the top and bottom parts are inserted onto a 35mm film canister, the spool and 35mm canister are physically larger than a 620 spool.  YOU MUST FIRST CHECK AND SEE IF A 35MM FILM CANISTER WILL FIT INTO YOUR 620 CAMERA.  Use an empty 620 spool for the takeup - it's easy to modify it by taping it to accept the 35mm film tail in the right place and make the slot thinner to grip the tail.The bottom part is printed as is.  The top part must first be rotated 180 about X or Y to sit flat on the bed for printing.  Now recommending 40% infill (even 50% is ok) due to the small cross-section of the splines.  Do not force adapters on.  Make sure the splines are aligned and if tight, trim/sand or wiggle on carefully.  The splines may need to be trimmed to fit Kalt bulk loading canisters and some others.The hole for viewing the film number (usually a red window) on the camera must be taped over with black gaffer's tape or some suitable opaque tape to avoid back side exposure of the film.  You will need to wind blindly about 1-1/2 turns at the beginning and taper down to 1 turn at the end.  Most medium format cameras have no rewind, so you will need to unload the film in a darkroom or changing bag and manually rewind the 35mm film back into its canister.  When processing, specify "process only" and "do not cut" and cut the film yourself.If you successfully use this in a 620 format camera, please add a comment with the make and model of your 620 camera so others can benefit.