I found this T-handle and liked the basic idea. However, looking at the files I recognized that the tip of the thread of the screw was screwed up in design (pun intended). Pretty simple, I corrected it in tinkercad. Then it dawned on me that a screw with a 4mm hole would be beneficial and followed a request and also made two even larger versions. The file names indicate the hole size, not the max size of the hex key! The 11-5mm is suited for up to 10mm.
After using them for a while I found that some keys really aren't perpendicular in the handle which is caused by then bend in the key. Simply chamfered the hole as much as possible and voilĂ , now it works better.
If you want it even larger, i.e. for a 1/2" key just take the 11-5 files (handle and screw!) and enlarge them in the slicer in X and Y to 127.5%.
The 7-3 screw fits into the 9-2 handle and the 4 and 6-3 in the small one (flipped).
Printed with 0.2mm adaptive layers and 20% cubic infill with double lines. No support.
The author hasn't provided the model origin yet.