I'm tearing down a dead electric scooter, with the intention of salvaging any parts that might be useful as spares for the scooter of the same model that replaced it. However, I've run into a problem trying to remove the front wheel/motor assembly from the bearing that allows it to be steered - it's being held in from the top by a kind of fastener I've never seen before, that I can only describe as an inside-out nut. It has a hex drive in the middle (17mm across flats), a flange on top (32mm diameter), and presumably is threaded on the outside (diameter probably in the 25-30mm range). It's sort of like a set screw, but vastly bigger than any I've ever seen. A 17mm hex key would get it out, except for the fact that the wires going to the motor run through the middle of the fastener; there's no way to get the wires out of the way without having already removed the fastener, and the scooter was obviously assembled with those wires in place, so there must be some sort of hollow hex tool that they used. The flange is fully recessed into the part that it attaches to, so there's no room for me to get vise-grips or anything like that around it.

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What is this sort of fastener called? More importantly, what is the tool called that is used with them? I can envision exactly what the tool must look like (something like a hex key with a slot down the side), but haven't been able to guess any search terms that would allow me to locate one.

  • Did you check both ends of the wire connections? If you can't pull them through, can you push them through? I think the key to your success is to get rid of the wires. Commented Sep 4, 2022 at 2:22

2 Answers 2


I built a tool like that once. It was for something I needed on a motorcycle. I started with a regular coupling nut.

coupling nut

The nut was just a bit too big. I ended up hand filing each flat until the fit was perfect. I placed half of the coupling nut in the thing I wanted to turn, and used a wrench on the other half.

In your case, I'm hoping the inner diameter of the nut would enable you to route the wires inside there. If the wire connector ends are too large, you could use a cut off disc in a grinder to create a slot. Kinda, sorta like a oxygen sensor slotted socket.

slotted oxygen sensor socket


The closest tools I can think of that would match this are tubular socket wrenches, aka box wrenches or tube spanners, or faucet wrenches. You should be able to run the wires through the center of the wrench. The trick is going to be finding the right size.

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