Can someone tell me how to remove this nut that is holding the chainwheel in place on this one piece crank? In the picture below, the red arrows are pointing to three slots in the nut that a tool would fit into to remove the nut.

Is there a name for a too like that? I looked on the park tools web site but I didn't see anything.

Is there a way to loosen it without having to buy a specialized tool?

Thanks in advance,

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  • I'm looking for a translation for the tool based on these German wikipedia pages: de.wikipedia.org/wiki/Hakenschl%C3%BCssel de.wikipedia.org/wiki/Nutmutter
    – gschenk
    Commented Jan 5, 2019 at 13:26
  • Maybe Parktool HCW-5 will fit? Commented Jan 5, 2019 at 13:27
  • A Hakenschlüssel is a hook spanner or sometimes C spanner (so spanner rather than key but a similar word)
    – Chris H
    Commented Jan 5, 2019 at 13:36
  • Yeah, in the US it's usually some variation of "spanner" (which is distinguished from "wrench"). Commented Jan 5, 2019 at 18:28
  • Some locknuts for bottom brackets used that kind of wrench. They were also in use for locknuts on old-style motorcycle headsets. So you might be lucky inquiring at a motorbike dealer/workshop.
    – Carel
    Commented Jan 7, 2019 at 12:15

3 Answers 3


Such a tool may be called hook spanner.

The nut is holding the inner race of the bottom bracket bearing.

A web search with "bottom bracket" and "hook spanner" produces a couple of hits. (For instance, the tool mentioned by Klaster in the comments.) You may use a vernier caliper to determine the dimensions of your nut and find the right tool for you.


Another option is to clamp the lower crank in a vice and use a hammer and brass drift into the three notches.

Downside, heavy blows are likely to distort the metal, so use more but gentler taps. A smaller hammer helps with control.

This is a one-piece crank, so they're not exactly known for having fine tolerances.

  • 1
    I'ev done this successfully recently (with a BB lockring on a beater bike). The thing I'd be wary of with this approach is doing it back up again - the hook spanner is much more controlled
    – Chris H
    Commented Jan 11, 2019 at 14:44

They come in various sizes. I think you need something like this: hook spanner

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