Nut, Crown lock


Old 06-27-08, 01:31 PM
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Join Date: Jun 2008
Posts: 1
Nut, Crown lock

Am working on an old Craftsman lawn tractor mower bed. The mandrel housing was broken and needs to be replaced. No problem - ordered the part [new part with a different method of screwing it onto the bed itself but that's ok]. My problem is removing the old pulley. It is secured with a crown lock nut and I have no understanding of that. I've researched on the web to have a better understanding and have figured out that the bolt is, most likely, intended to prevent removal of the entire shaft and bearing when in use. Initially, not understanding the purpose of a lock nut I blasted it with Liquid Wrench. What I need is someone to tell me how to remove a lock nut. Do I need a special tool? Sure, I can replace the entire pulley system but would still need to remove the old stuff, probably with a saw. Would prefer to use that which is still usable instead of spending money. Any insight from anyone would be a blessing to me. Thank you
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Old 06-27-08, 06:46 PM
Join Date: Jun 2008
Location: GA
Posts: 150
A crown lock nut looks like this:

The top of the nut is deformed so that it grips the bolt with considerable pressure without damaging the threads. They're often used to set the preload on bearings or to set the brake clearance on an electric clutch assembly.

You should be able to get it off with a regular wrench, but it'll take quite a bit of torque. Putting oil on it will help. Keeping the bolt from turning can be a problem on something that's broken.

Can you post a picture or diagram of the assembly?

Old 06-27-08, 11:19 PM
bontai Joe's Avatar
Join Date: Apr 2004
Location: Pennsylvania
Posts: 592
No special tools needed, just a regular wrench or socket. As stated above, that kind of nut will grip the threads all the way off, so there will be no breaking it free with a wrench and then quickly spinning it with your fingers to get it off, you need to wrench it all the way off. Only "supposed" to use them once as they are not designed to be reused, they don't grip as tight the second, third or 9th time. But I have reused them myself when I had to with no problems.

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