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Do the HGR studs meet or exceed the mechanical properties of MIL-F-5591?

Do the HGR studs meet or exceed the mechanical properties of MIL-F-5591?

MIL-F-5591 is an older spec replaced by NASM5591 and I can see no difference in either spec.  It is a somewhat questionable spec that does not perfectly apply to  parts except for the tensile-shear performance numbers.  The cycles for the HGR series is a pipe dream in my experience in testing every manufacturer's part I can test.  I have never seen parts go beyond about 15,000 cycles.  The pins are worn in half and/or the receptacle ramp is worn out.  The spec allows a drop of oil and that makes a ton of difference in cycles.  But I have never seen anything close to 40,000 honest cycles in anything.  Thus, I feel this spec has much to be desired.  We try to advertise that we cannot meet the cycle performance.

Neither spec calls out stainless yet it calls out aluminum but then suggests heat treat.  Even expectations of MIL-F-5591 but they infer they can meet 40,000 revs on a HGR part while I have never seen a number close to that.

So, I would use the spec as a guide for tensile-shear, torsion, vibration, etc. and nothing more.

When they began making 300 series HGR studs, in some drawings, they reduced the tensile-shear ultimate to 730-750 lbs-f.  When we began making our own studs, our goal was to bump the number back to 1,050 lbs-f.  We did this by increasing the pin diameter and the stud shank diameter.  What I was really addressing was torsion resistance where the average user would overtorque the stud and wonder why the pins became loose. When we were selling the parts, I typically saw returns daily with studs with missing pins.  We fixed a known problem without interfering with forn, fit, and feel.


Our machined studs are 303 stainless and headed studs are 302 stainless.  Pins are 17-4.  Cups are 303 and 303.  Springs are 302.