HST315-5-_ Hi-Lite with HST1071TAWT5 Collars

[bryancobb]

I need to touch-base with a very knowledgeable person who has a significant amount of hands-on experience with these fasteners.
I am experiencing some anomalies that I do not understand and I am hoping someone has experienced the same thing I am seeing.

I won't waste anyone's time explaining unless some who has installed and used a lot of these pins replies.

Regards,
Bryan Cobb
Manufacturing Engineer, Aerospace

 

[WKTaylor]

BC...

RE Photo... This is OBVIOUSLY NOT an HST315 pin =>Hi-Lite Pin - 130-Flush Crown Shear-Head - Titanium (nominal Dia)

OK, What is it REALLY...?

Looks like a protruding head blind rivet or bolt with a damaged/banged-up 'pull-pin'... but otherwise this photo is inscrutable.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[bryancobb]

Wil,

This is occurring during new assembly on the manufacturing floor.

It IS most certainly an HST315YV5-5-__ Pin with an HST1071TAWT5 collar that did not ever reach the proper
torque of 20-30InLb. Before it reached that prescribed torque, the head failed around the full perimeter
of the pin shank creating a donut of Titanium FO about 0.3125" O.D. Not enough size to crash an aircraft
but plenty enough mass to damage turbine blades.

I have tested a handful of the collars. They always perform as designed at between 23InOz and 26InOz.
Two different manufacturing lots of pins have had their heads fail in similar fashion. The holes are in
a cured carbon prepreg item and are hand countersunk with a piloted, 1/2" OD, 130 Degree carbide c-sink
with a Microstop. Microstop depth is set to result in the crown of the properly installed fastener head
being 0.006" above the surface.

Pin is being wet-installed with PR1775 Sealant or something like that.

Head Failures are happening on approximately 5% of fasteners whether installed by hand ratchet with hex
wrench through, and/or a properly setup Hi-Lite Installation pneumatic tool.

A small group of we engineers are having trouble finding the cause of the head breaking away.

 

[bryancobb]

Any Ideas?

 

[rb1957]

are we back to "bogus bolts" again ?

that looks like the head, with "HST …" stamped on it. How is it getting damaged like that ? Looks like it was done with vise grips ??

another day in paradise, or is paradise one day closer ?

 

[bryancobb]

rb

Please read. The head failed during installation being done by a well-trained operator
who was using the correct tools, and going into a properly countersunk hole in carbon fiber.
The head pulled off BEFORE the shear collar reached torque.

 

[WKTaylor]

BC...

https://www.lisi-aerospace.com/en/product/hi-lok-and-hi-lite-fasteners/

Scroll down to "HST™ pins configurator"... open it up... then scroll down to 'Custom [Pins] Drawings' window...

HST315 [Nom] * HST415 [1/64 OS] * HST515 [2/64 OS]

Click-on/open-up HST315...

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[bryancobb]

I already had the product datasheet. I've read every word of it several times in the past few days.
I still can't think of any reason the heads would be failing BEFORE the collar reaches 25InLb.

 

[rb1957]

this is sounding odder and odder !

Brian, I didn't mean to imply that you had installed the bolts incorrectly, I "only" said it "looks" like …
I'm guessing they used vise grips (or something like) to grab hold of the head and pull it out.

But if those were CSK head Hi-Lites, man those heads are really damaged by extracting them !

that then suggests "why were they so difficult to remove?" If the nuts failed at such a low torque, how did the fasteners seat so well ?

and I return to my first line … maybe we're dealing with bogus bolts ? as the bolts fail at the nut.
Have you tried torquing the MS nuts on to a bolt on a sample piece ?

You've said, and I take you at your word, that you've done everything by the book ... therefore the nuts should not be failing.

another day in paradise, or is paradise one day closer ?

 

[bryancobb]

Thanks RB,

The pin was still in the hole after the head failed and I used the collar to pull the pin out of the
back side since the head was totally gone. I actually was able to use my fingers to grab the collar and
pull. No Vise-Grips or pliers. Nothing was clamped on the head. It failed like that. Approximately
20 have failed out of 200 installed.

The NUTS never failed or never sheared off. The heads fail first.

 

[WKTaylor]

OK, OK, OK... HST315... REF specification drawing cited in previous post...

-5 = 5/32 Dia... smallest dia... extremely thin 130-deg shear head... this makes the installed collars much more important to avoid head fracture...

Embedded within HST315... upper RH corner of the spec drawing => "TYPICAL COLLARS: HST71, HST97, HST1094, HST1097"

HST71-5, HST97-5, HST1094-5 & HST1097... collar torque-break-off => 15-to-25in#

WHY... HST1071TAWT5...?
HST1071-5 collar torque-shear/break-off => 20-to-30in#

CAUTION.
An 'integral-washer-collar' will likely induce a significantly higher torque-tension for 'same torque' relative-to a 'plain' collar [due to lower torque-turning friction]. A #5 just doesn't seem to warrant the NST1071TAWT5 collar... which could easily over-stress the head...

NOTE.
I have had a LOT of #5 100-deg flush shear-head titanium HL-pins fail... heads dish/crack symmetrically/circumferentially or off-to-one-side… because of off-angle [NOT 100-Deg+/-1-Deg] countersinks… and/or the CSK is canted-off-angle or shifted-off-centerline relative to the shank of the pin... these Csks defects and higher torque-break collars are a set-up for failure.


Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[rb1957]

The CSK head failed ??!!

It sounds like the collar break-out torque is too high for your bolt. Have you talked to Lisi (or Peerless or whatever they call themselves today) ?

If you were to use an MS nut, what torque would you specify ? the 2 in.lbs that seems to be working ?

another day in paradise, or is paradise one day closer ?