How do you go about checking threads to make sure that the threads are cut to a UNJ spec insted of a standard UN?
How do you go about checking threads to make sure that the threads are cut to a UNJ spec insted of a standard UN?
My understanding is the "J" threads have a more generous root radius (bottom of the thread on outside threads) to lessen stress concentrators thus making the thread less inclined to fail at a given tensile pull.
Depending on the size of the thread, use a radius gage, whip up some plaster and make a cast, then use a gage or optical comparator.
http://www.eng-tips.com/viewthread.cfm?qid=103251
In reply to 914Driver:
We have a UNJ thread on one of our parts and I am not sure that the manufacturer is cutting it. I will try the plaster cast.
914Driver wrote: My understanding is the "J" threads have a more generous root radius (bottom of the thread on outside threads) to lessen stress concentrators thus making the thread less inclined to fail at a given tensile pull.
You are correct sir.
Good luck checking them.
What is the radius used on a 2.125-12 UNJ thread? I am having trouble finding it. All that the Machinery's Handbook says is that it has a .15011P to .18042P radius at the root of the external thread.
Edit: Found it.
.15 - .18 P = .0125 - .0149
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