Allen Key to Hex Bit Adaptor - REMIX for 4mm Driver

I bought a boxful of M3 hex head bolts in a whole load of sizes with nuts and washers for building 3D printed projects. 

Then I bought a Hychika mini-electric screwdriver on Amazon which has about 50 screwdriver bits of all sorts, including some hex drivers. 

Then I realised that despite including H0.9, H1, H2, and H3 bits, the Allen key for my M3 bolts is H2.5. Aaaaaaaaaaaargh!!!!! 

I've ordered an H2.5 from Aliexpress now but it's months away from being here, so I wanted a quick fix now.

I tried resketching over the original model and narrowing the driver end to 4mm, but that ends up so thin due to the cutout to admit the Allen key that the torque test failed at 0.1Nm which was hopeless.

So I redesigned it from scratch making the Allen key end much thicker and fixing the key in from that end, locking it in with an insert like the original design only at the other end.

This turned out MUCH stronger, and I aborted the torque test at 0.4Nm because the little electric screwdriver maxes out at 0.25Nm and at that stage you're better off detaching the screwdriver and finishing off the tightening by hand using either end of the Allen key (still in the adaptor) according to access.

It's a bit fiddly to make. Being tall and narrow, I used a 3-line brim to ensure adhesion and had no problems. You want it as strong as possible so set it at 5 walls (for a 0.4mm nozzle) and 6 tops/bottoms, then there's no need to specify infill as it's all walls. I used 0.2mm layers. No support needed on either part.

I used PLA+ but if you have anything stronger then use that.

I sketched the driver end to be flat-to-flat 4.1mm because after it has been in and out of the 4mm driver a few times the rounded edges of the printed lines wear off a bit and it ends up a bit loose. At first it will fit quite tight so be careful until you've worn it in (or carefully file/sand the hex faces).

Then put a dab of superglue in where the Allen key fits, and hold the key in until it's gripped. Then glue in the retaining insert, concave face towards the key, flat end at the end of the adapter (angled end is to accomodate the curve at the bend in the key. Doesn't really matter if the end of the insert doesn't quite line up with the end of the adaptor but you can fiddle around with a file and tweak it before glueing if you like! I clamped my insert in place until the glue was fully cured.

The original designer wondered if the insert could be given some metal to attract it to a magnetc driver chuck, so I had a go with a 1" nail (a 2d or tuppeny nail for those who know those sizes!) and it actually works. Not only that, the presence of a glued nail down the middle of the narrow parts of the 4mm adaptor substantially increases the strength, so it's a double-win. Unfortunately not all screwdrivers will have exactly the same chuck so you might have to experiment with nail length, maybe even having it stick out a bit so it reaches the magnet at the back of the chuck. Mine was just right flush with the end of the adaptor. I had to file a little off the diameter of the nail head so it would slide into my driver chuck.

Sketching the correct size hole for the nail (2mm) had unexpected results in the slicer, empty space in the print around the hole, so I sketched it at 1mm and the print is far better and completely filled, you just need to follow the hole with a 2mm drill to get it the right size to admit the nail. I cut my nail to length - the hole is 16mm deep, dabbed superglue on the hole and along the nail and pressed it in. Job done! The whitish appearance of the driver end of the adaptor in my photo is just a haze of superglue residue which has been whitened by my accelerator spray, not very pretty but completely functional.

Thanks to the original designer for the design concept, even if I have departed substantially from it here, it inspired me to adapt it for my needs.

Please Like this model if you find it useful.

If you REALLY like it, https://www.buymeacoffee.com/gigabeast :o)

Re-imagined from scratch for 4mm chuck screwdriver (mini-electric screwdrivers), this model is currently just for 2.5mm Allen key for use with M3 hex head bolts.