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I want to attach a 12 toothed spur gear with a bore diameter of 6mm onto the shaft of this motor (6mm diameter). How would I go about doing this? From what I see, the shaft is smooth so is my only option to find a gear with a set screw? Or is it sufficient to attach a gear with no set screw and simply rely on the friction of the bore? The torques will be low.

Are there any websites that one would recommend for finding gears like this? I'm finding it impossible to find gears with a module of 1.0, bore diam. of 6mm, and a thickness of less than 20mm to fit onto the shaft.

Any help would be greatly appreciated.

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Here you go: https://uk.rs-online.com/web/p/spur-gears/8787907/

1 Mod 12 Tooth Gear

The trouble is that a 1MOD 12 Tooth gear has a pitch diameter of 12mm, i.e.the bottom of the teeth is less than 12mm, so once you drill a 6mm hole through the middle there's really not much material left at all to make a hub from.

What is the specific requirement or constraint that means you need this specific gear on that specific motor? You may find there is a more robust and elegant solution if you can be more flexible in your approach, but without the information, I can't help any further.

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  • $\begingroup$ I was hoping to get a 10:1 - 12:1 gear train with only two gears, but I suppose if I dropped the two gears requirement I could achieve this more elegantly with two coupled intermediate gears. en.wikipedia.org/wiki/Gear_train#/media/File:AnimatedGears.gif Also, I was under the assumption that the overall length had to be less than or equal to the motor shaft length (20mm) but I realise that may not be the case? $\endgroup$ – Inf_E Dec 16 '19 at 10:16
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What are the respective tolerances on the “6mm”?

Either it will be a press fit which will be sufficient to handle the torque and shock loading or it will not.

If not, then you have to fit set screws and even machine a flat on the shaft.

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Boston Gear or McMaster-Carr might have suitable off the shelf gears. You could also press the gear onto a hub that has a set screw. I would avoid pressing anything directly onto a motor shaft, you could bend the rotor and/or damage the internal bearings.

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  • $\begingroup$ Many motors have both ends of the rotor available just to allow things to be pressed on - even have easily removable dust covers, this avoids any bearing damage etc $\endgroup$ – Solar Mike Dec 13 '19 at 15:46
  • $\begingroup$ Indeed, the datasheet for the motor linked by OP suggests a max force for press fitting of up to 3kN if you support the shaft! $\endgroup$ – Jonathan R Swift Dec 13 '19 at 15:54

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