The updated V2 version is out now, check it out! 

I made this model because I couldn't find one that met all my criteria:

Fully 3D printable (No screws, glue, etc.), 

Center mounting,

Horizontal orientation,

Access to all ports and buttons,

Strong grip on both the phone and the handlebar,

Support-free printing.

Designed to fit standard 31.8mm (1.25") diameter MTB handlebars, 25.4mm (1") spacer included. For 22mm, check out the remix by moWerk, and Shaun577's remix for 35mm handlebars.

Can hold 65-80mm wide phones. (Pretty much all phone models are in this range).

Easy to print/assemble/use, no supports/rafts/brims are required, no bridges or extreme overhangs.

There are two types of knob screws: the normal one and the stronger one. The normal one is a single piece part and it rotates more freely. The stronger one is… well, stronger.

Pay attention to your handlebar stem sizes. In my case there's plenty of room, but it might be too thick to fit on some bikes.

Print settings:

Layer height of .12mm is optimal for the threads, everything else can be printed in .2mm using adaptive layers

3 Wall loops work the best

If you choose the normal knob, use  100% infill. (Or just don't tighten it too much)

The “All in One” model fits on a 15x15cm bed and has the stronger knob by default

 
 This is my first somewhat decent model. Please, leave your feedback if you liked it.