Problem with coupling thin motor shaft!

I have a thin shaft motor with shaft being barely 1.2mm thick in dia. I need to couple it with a thicker shaft which is about 3 mm thick. Please help me find a coupling solution!

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AndyGadget7 years ago
Cut a length of heatshrink sleeving to length. Put a tiny dollop of superglue on each shaft, then butt them up into the sleeving.  Shrink the tube (ideally with a hot-air gun, but gentle rubbing with a soldering iron will do at a pinch) and you'll have the two shafts coupled with just a tiny bit of flexibility - Perfect!
In the absence of a lathe to knock out a quick shaft coupler, that's how I'd do it too.
rsatheesan1 year ago

use a simple screw connector

shumroger85 years ago
I have such coupler for 1.2mm to 3.0/3.17mm
or 1.2mm to 1/8"

If you need such coupler, email to and ask John for this.
I did this once using a spring from a clicky-type ballpoint pen.  The attached picture shows this little spring connecting the shaft of a DC electric motor to the shaft of an optical encoder removed from an old computer mouse (a mouse dating back to the old days when mice had balls, if you'll excuse the innuendo)

I soldered it into place on either end of the spring, and I can't remember the exact details of this, but it might have taken a little extra finesse to get the solder to stick to the motor shaft.  I mean I think I had to use a lot of heat to get it to stick, but at the same time I had to accomplish this somehow without melting/ruining the motor. So that part might have been tricky.

Another caveat:  I don't know how much torque this little springy linkage can withstand.  For my application I just needed it to spin freely. The encoder doesn't add much in the way of torque.
Burf7 years ago
Those are awfully small to try to couple together by any means short of welding or using some high strength epoxy. You might have better results by using gears of the same size and pitch, with hole diameters matching the individual motor shafts.
Re-design7 years ago
How about a tube on the larger one and a tube on the smaller one.  THe smaller one fits inside the larger one and a pin is drilled thru both of them.  You can crimp, clamp or glue the tubes on the shafts.