This is a simple fly fishing reel I designed for myself a few years ago but am posting it by request.
I've used a few versions of it for everything from bass to panfish and I actually used one to catch my first trout (on a fly) with it. (see picture)
The reel does use a few bits of non printed hardware.
(1) 10-32 x 1" Socket Head Screw and Nut
(1) 4-40 x 1/2" Flat Head Screw
(3) 1/4" X 1" Fender Washers (Lowes - Item # 136616 Model # 880342)
(1) Spring & Ball (optional)
See exploded diagrams for assembly.... I don't have time to do a full write up right now but here's some misc. info I remember.
The spool halves get super glued together.
The fender washers act like a bearing and make it the reel spin more freely. (I tried a thrust bearing but it really wasn't worth it.)
This is a Click and Pawl design reel - The spring and ball for the clicker can be a Pen Spring and a BB but they will rust over time. I used a .186" chrome ball (Honda Motorcycle Part# 96211-06000) I also used a cut down stainless steel spring I found locally. Use a small Allen wrench to press the spring and ball into the hole while pressing the spool down. It's a little tricky but not impossible. :)
You can use the printed clicker (not show in the pictures) it clips right in the bottom cut out of the spool post on the reel frame. I don't remember which stl version I went with or what the printer settings I used were so I included a bunch of different versions with different sized nubs I was testing so you can play around with them if you want.
The hole for the spool bolt was left small and tapped with a 10-32 tap but you can probably just force the screw in.
The nut for the spool is embedded into the actual thumb knob during printing and requires a thin nut. (I used a 18-8 Stainless Steel Thin Nylon-Insert Locknut from Mcmaster Item# 90101A225) You could probably just use a nut and washer but seeing it's used to set the drag of the reel (so to speak as it is just a Click and Pawl design) it might be hard to adjust in the field without a tool if you went that route.
Fly_Reel_Thumb_Knob_Final.STL uses a Thin Nylon-Insert Locknut with with these specs
Fly Reel Thumb Knob Full Size Nut.STL uses a full sized Nylon-Insert Locknut with with these specs
For drag after hook up it was designed so you can also just use your hand on the out spool edge to control the drag if need be.) I've never caught anything big enough yet to worry about it though.
See http://imgur.com/a/da9rE for a few more pictures I took during the design process.
Anyway that's it for now if you try to print this and have any questions.. ask and I'll try to answer them.