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I need to attach a 3/4" shaft to a 1/4" motor shaft. Looking for a place to buy it or how to make it? Answered

I basically need to attach a motor with a 1/4" shaft to a 3/4" threaded rod. I know they make shaft couplers with set screws, but I have not seen one with that big a difference in bore DIA. I attached an image to show you what they look like.



Best Answer 9 years ago


Look at the bottom of the catalog page (1154). As Steveastrouk said, bore side B is meant to be machined to size. In your case, catalog #3084K33 (3/4" to 0.235") is what you need.

The fact that you've got a 3/4" threaded rod might make things more complicated. You really need a coupling nut (put that into McMaster-Carr's search box), but they don't come 3/4"-to-1/4".

That's ok. I will just drill a hole straight through the threaded rod, then use long set screws. Thanks for the link!

On a more practical note, are you sure this is what you want to do? Does your motor with the 1/4" shaft have enough torque to actually drive whatever you have mounted on the 3/4" screw?

It is a 4.3 V 3A motor with 72 lb-inch torque. I am pretty sure it can handle it.

You'd usually buy a "piloted" bush, and bore out the bit you want bigger. You could probably ask a local machine shop to make one - there's half an hours work in it. Steve