i'm trying to connect a D-cut shaft to a plate for transmission of torque

enter image description here

This is the motor that i am using with a 'diameter' of 4.5+/-.1mm

My first question is whether I can use 5mm circular universal mounting hub like this to do so? enter image description here

Secondly, i have access to a a laser printer. Would you recommend making a mounting hub similar to the one shown above but with a D-Cut hole? It has a precision of .2mm, so along with the uncertainty in the shaft of 0.1mm, I guess I would have to make the 'hole' 4.8mm. Would this potential difference in size mean that the torque may not be transmitted efficiently?


1 Answer 1


In answer to your questions:

  1. Yes, you can (and should) use a standard 5mm hub, such as the one shown in your question. The flat on the motor shaft is only there to provide somewhere for a grub screw to bite in (better than having a perfectly rounded shaft).

  2. No, I would stick with a standard hub with a circular hole, for the reasons stated above. I don't know what the tolerance is on your hub, but it should be a tight fit around the shaft (5mm +0 -0.012). Ignore the 4.5mm dimension, that's just the flat for the grub screw, it's irrelevant.

  • $\begingroup$ Ah, Thanks for clearing that up. The 4.5mm dimension doesn't really matter. .. The uncertainty on the 5mm hub is 0.2mm. Would the hub still fit if the hole is 4.8mm while the shaft is 5mm? Thanks $\endgroup$
    – Yogi12
    Feb 23, 2018 at 16:19
  • $\begingroup$ What do you think? Trying to a 5mm diameter shaft into a 4.8mm hole? No, it wouldn't. You would need to ream out the hole in the hub to 5mm (typically these are made of aluminium). If your shaft diameter is between 5.000 and 4.988mm, you probably want a hub with a hole diameter something like between 5 and 5.1mm. $\endgroup$
    – am304
    Feb 23, 2018 at 17:01
  • $\begingroup$ You could make it fit with a 100 ton press but it would not be very useful after... $\endgroup$
    – Solar Mike
    Feb 24, 2018 at 9:52

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