Decided to build a LED swing arm work flood lamp and needed some knobs that I could loosen and adjust the light to another position with out the use of a wrench. The normal round knobs just didn't feel right plus I wanted something with a little more torque to really hold the flood light steady, so I designed this. The hardware I used was 5/16" so I designed it to use a 5/16" nut. Printed it inverted so the only supports needed were the inside area where the nuts goes, I also printed this with 100% infill to make it strong (I print only in ABS so it's really strong anyways). The nut simply drops into the hex hole and is held in place by the bolt so I didn't glue it into the handle, if this is something you going to unscrew completely then you may consider a dab or two of epoxy to hold it in place. Right now this is only for a 5/16" nut to go into so you can re-scale it to fit any size you need, I many upload a 1/4", and 3/8" size at another time.
UPDATE: I just added a 1/4" version
Raft or no raft? Up to you! I like rafts because even it the print bed is a little unlevel the raft will make up for it, and with this having the internal supports for the nut area it allows better adhesion for them.
Clear out supports. if the nut is really tight going into the hole you can always use a bolt to pull it into the bottom of it. I left a little wiggle room in the design due to printing in ABS and allowing shrinkage.
Designed with 123D Design and printed with Simplify3D