NAF-PH4 strain relief
NAF-PH4 strain relief
(OP)
Does anyone have information or a copy of NAF-PH4? Many older drawings (1950's era) refer to this specification for strain relief of springs for aircraft use. As far as I can tell this is from the Naval Aircraft Factory (NAF).
thanks
thanks





RE: NAF-PH4 strain relief
and see if they can get you a copy. That is the website that we get all our DOD specs from.
RE: NAF-PH4 strain relief
RE: NAF-PH4 strain relief
RE: NAF-PH4 strain relief
RE: NAF-PH4 strain relief
RE: NAF-PH4 strain relief
coiling --> LTHT --> grinding --> shot peening --> LTHT --> coating --> pre-setting
The first LTHT is mostly for relieving the tensile residual stresses that are introduced during the coiling process. The second LTHT is not really a stress-relief treatment, but instead increases the yield point due to strain aging. People can become confused if the term stress relieving is used to describe both treatments, because they really are two different steps with two different goals.
RE: NAF-PH4 strain relief
Also, MIL-S-6715 para 3.12 provides strain relief temperatures of 350 deg F (1 hr) to 600 deg F (10 min). Is this typical for strain relief?
RE: NAF-PH4 strain relief
Here is a typical manufacturing routing at my facility.
Coil
Stress Relieve
Grind (if ends need it)
Shot Peen (if calculated stresses are high enough to warrant it)
Stress relieve again (only if peened)
press (to remove initial set, but only if calculations warrant it)
Rust preventative coating
Inspect
Ship
I will tell you this, never, and I mean never try to tell the manufacturer how to make their parts. They are the experts, just tell them what you want, and let them decide. Nothign irritates me more than a customer that trys to tell me how to run the parts, especially when half the time they have un-needed steps that are costly and do nothing. If I come across that, I usually quote the job much higher than I normaly would because of the time wasted...
RE: NAF-PH4 strain relief
RE: NAF-PH4 strain relief
RE: NAF-PH4 strain relief
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RE: NAF-PH4 strain relief
Springs taking set the first time they are cycled are unknowledgeable designer fault. Most mechanical engineers do not even know what it means, what it gives, when to use it, how to calculate it, etc. Knowing the formulas for spring deflection and spring stresses due to deflection or load is definitly not enough.
http://israelkk.googlepages.com/home
RE: NAF-PH4 strain relief
I just wish they would listen to those of us that deal with it every day and believe what we tell them... oh well, more $ out of their pocket when they have to have us re-process the parts for them.