T-Handle Hand Drill (REV 2, Parametric)

I got tired of grabbing my cordless drill to clean up holes for M3 screws in my prints, so I made this handle.  It is intended to enlarge or cleanup existing holes.  If you need to make a new hole I recommend using a power drill since the result will be much cleaner and straighter.  

Revision 2

I updated the design to use socket head cap screws and square nuts.  Button head screws will still work of course.  With more experience, I also improved the CAD file.  It is much harder to break any of the operations.  Screw length now determines the handle thickness, and I double check that the handle length is sufficient.

Supplies

You will need:

• 3.1 mm drill bit (https://www.amazon.com/uxcell-Straight-Ground-Titanium-Diameter/dp/B099JJ85HC/)
  • 1/8 in drill bit (3.175 mm) could also work - go up one step in clearance 
  • 3 mm drill bit could also work - go one step down in clearance 
• (5) M3 square nuts (DIN 562)
  • or (5) M3x5x4 heat set inserts
• (5) M3x12 SHCS

Clamping & Tolerances

In order to prevent the drill bit from slipping, the screws that clamp the drill bit in place need to be very tight.  The cutout diameter cannot be too large.  Even after adjusting tolerances for dimensional accuracy, I downsized the hole to get enough clamping pressure to lock the bit in place.  (In the parametric design file, the user parameter “drill_actual” has a -0.2 mm adjustment.)

Notes

I recommend using a 0.1 mm layer height and 0.4 mm nozzle diameter for the best success.  I used 0.24 mm for the first layer, but this should not have a large effect.  

If you want to use a custom drill bit, I have included a step file suitable for drill bit diameters up to 5mm.  Use your favorite CAD to extrude the hole.  If you want an entirely custom handle or other modification, I include the f3d file with design history.  The primary design elements have user parameters.  

Minor update: I reorganized the downloads so that individual parts are separated into their own file, and compatible parts are bundled together into a zip file.  I still include stl and step files.  

Thanks for visiting, and enjoy!