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Where a turned thread meets the full diameter shaft

DanielG

Stainless
Joined
Oct 22, 2014
Location
Maine
If you turn a thread onto one end of a shaft, you can either put a thread relief in, or you can have a section where the threads get shallower, i.e. tool moves out in X as it still moves in Z. What is the actual name of the latter feature? I can't find it in Machinery's Handbook.
 
If you turn a thread onto one end of a shaft, you can either put a thread relief in, or you can have a section where the threads get shallower, i.e. tool moves out in X as it still moves in Z. What is the actual name of the latter feature? I can't find it in Machinery's Handbook.


The official term is STUPID!

Another name is "Point of Failure"
 
Wait!

Isn't it a "Laterally displaced inverse Higby cut"?

I'm sure there is a reference somewhere on the interweb
 
The official term is STUPID!

Another name is "Point of Failure"

Completely agree Cal, ....back in the day, one customer insisted on it, .........and while I could do it quite easily on an engine lathe (you get the knack once you've busted a few threading tools :D ) I never liked doing it or the finished look of the job.
 
The official term is STUPID!

Another name is "Point of Failure"

Nearly every commercial made fastener runs out vs having a relief cut, because they're almost all rolled vice cut. So you're saying almost all fasteners are stupid?

Critical fasteners will have reduced shanks that are smaller OD than the thread ID to have more predictably controlled failure, whether cut or rolled. A precise relief cut would usually equal the thread ID and would function basically in the same manner but is not as predictable. But both are designed points of failure much more so than a thread that runs out.

A failure in a standard bolt is very likely to occur somewhere in there threads, but not likely in the runout because there is more material there. Either way it's not predictable so you don't design anywhere near it and it's certainly not a designed failure point.
 
Nearly every commercial made fastener runs out vs having a relief cut, because they're almost all rolled vice cut. So you're saying almost all fasteners are stupid?

Critical fasteners will have reduced shanks that are smaller OD than the thread ID to have more predictably controlled failure, whether cut or rolled. A precise relief cut would usually equal the thread ID and would function basically in the same manner but is not as predictable. But both are designed points of failure much more so than a thread that runs out.

A failure in a standard bolt is very likely to occur somewhere in there threads, but not likely in the runout because there is more material there. Either way it's not predictable so you don't design anywhere near it and it's certainly not a designed failure point.

World of difference in grain structure for rolled vs cut threads.
 
World of difference in grain structure for rolled vs cut threads.

Yes, but everything I said applies to either rolled or cut. Thread runout is neither stupid nor a failure point as demonstrated by the overwhelming majority of commercially available fasteners.
 








 
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