DIY horizontal encoder explorations

EVQWGD001 horizontal encoders are quite expensive, no longer manufactured and have the worst mounting system one can imagine in my opinion. So I want to design an alternative roller with similar dimensions based on a mouse wheel encoder and I need your help!

The idea is quite simple. The system consists of only 5 parts: mouse wheel encoder, wheel itself, axle this wheel is mounted on, some kind of support for the side opposite to encoder (may include a bearing for smoothness) and the base this whole contraption sits on. There are some ways to add a push button too but that's for another time.

In search of an axle

The hardest part for me in all this is making an axle. The encoder hole is a hexagonal shape with very tight dimensions: exactly 1.73mm side to side. The axle needs to be made of a rigid material such as metal or non-flexible plastic.

Ideas

DIY solution comes in two parts. Firstly, choosing the base material or product that can be turned into a solid hex rod. Secondly, processing the blank to turn it into said rod. However I'd like to avoid a lot of manual processing (time = money).

Here are some available materials and techniques that I thought of:

1. You can't use a hex key as an axle (very unfortunately) as those come in 1.5mm and 2.0mm variants only. I tried just in case — they don't fit.
2. I found some hexagonal RC car axles on Aliexpress that are 1.8mm and may fit but those are quite expensive which defeats the purpose of the project.
3. Toothpicks have fitting parameters but are quite flimsy and probably aren't great for a long-lasting component... unless they are stabilized? 😆
4. 2mm brass wire can be filed to shape manually
5. 2mm steel axle can be ground with power tools
6. 2mm ABS plastic rod (square or round) can be cut with a knife or sanded
7. 2mm transparent acrylic rod can be filed or ground
8. Metal blanks can be CNC milled (probably not the most optimal method but I don't know better except cold-drawing which seems way out of reach)
9. Resin/epoxy can be cast in a mold
10. Metal casting is also an option
11. 3D printing SLA — not sure if the tolerance of 0.1mm would be good enough

If you have better ideas, let me know!

My experiment

The best solution I got for now is to use 2mm brass wire and file it down to hex shape manually. Brass is a malleable metal that is easy to solder and bend but it was extremely hard to do accurately. The first one turned out a complete mess so for the second attempt I somehow screwed on an M2 nut to keep track of the edges better.

As for the roller wheel, I bough an assortment of different components that can be used as one. The original wheel has the length of 12mm and the outer diameter of 12mm as well. So I bought some brass inserts and knurled thumb nuts that were close to this size.

The best one turned out to be the 10mm long M10 brass insert with outer diameter of 12mm. 10mm ones are all too small: I feel like even the small encoder has too much turning resistance for such radius. Gears would be necessary to increase the torque.

I used a brass insert, a small circle cut out of a thin brass sheet and two pieces of brass wire to solder this “beauty” of wheel:

On the other end I used a simple PVC stand with a hole, a cut out plastic tube that just so happens to perfectly fit a tiny bearing. I wish I recorded how that rotates — it's so satisfying!

Due to the friction in the encoder itself, I think the bearing is actually not doing much. Also of course this whole thing is very imprecise and wobbles a lot. Pretty good for a test still!

I spent almost a whole day on this. And I definitely don't want to make more until I find a better way to get axles. After the axle is found, it shouldn't be too hard to mount pretty much anything you want on it. Of course the wheel will need an appropriate size hole too, but that can be friction-fitted or glued in place and doesn't require such tight tolerances.

Update September 2022

I found this steel axle on AliExpress: https://aliexpress.com/item/1005004520980241.html. It is a veeeery tight fit because it's 1.8mm in size instead of 1.7mm. I have to force it in with pliers because the thin axle is hard to grab with hands so firmly, but it works quite well and the quality is great. Also it's very hard to take it out even with pliers. It's quite hard to sand it as it's made of steel however I tried filing it and it takes about one minute to make it easy to put in and take out. Next gonna work on some encoder wheels to go around this axle! So far it's a great success! ⭐

I also bought 1/16" Allen/hex key and although it's very close to fitting, it wobbles a lot and sometimes turns inside of the hole. It also has a huge amount of pre-travel before it actually catches on to the encoder walls and starts turning it. Not a great option!