HiLites in Clearance fit holes 1

[MRBDUDE]

I am looking for any information on hilite installation in clearance fit holes. The stackup is aluminum/aluminum/CRES Specifically if anyone has experienced movement or "working" on this type fastener in a highly loaded or pressurized joint. The condition is noted by swirl marks in the paint on the fastener heads. Flush head fasteners. Thanks for any input.

 

[rb1957]

don't install fasteners into out of spec holes. there's no such thing (IMHO) as installing a HiLite into a clearance hole, as the spec requires a small interference. If the hole is too large then use an oversize HiLite.

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

 

[WKTaylor]

MrBdude...

Hi-Lok [HL] pins/collars were originally designed for installation same as swaged-collar lock bolts and nuts/bolts: clearance fit in good-quality drilled tolerance holes. For this reason don't spend Your fastener budget for Hi-Lite pins when HL pins are 'good-enough'/better-than Hi-Lites in the application You describe.

HL pins do NOT tolerate installation in true interference-fit applications: The shank-to-thread transitions are rather sharp-edged so don't install HL pins in anything more than 'net-fit' [Boeing: transition fit] applications. In true interference fits, HL pin shoulders tend to damage undersized holes when shoved down the holes. NOTE: every bolt design has this same quirk... sharp transition shoulder between shank and threads. Then only practical way to install HL pins and flush/protruding head bolts of all kinds [with precision Dia shanks] into interference fit is by using 'shrink-fit'/freeze-fit methods [preferably dangerous liquid nitrogen]... and even this method requires the mechanics to become 'paper-hanging acrobats'.

The next evolution pin/collars were Hi-Tigue [HT]... which are like Hi-Loks in every respect... EXCEPT the shank-to-thread transition shoulder has a rounded bulge... and are intended for installation in true interference fit application. 'In-Theory' the rounded bulge facilitates installation in high interference fits... by 'stretching/smoothing/rounding' the hole surface [improving the hole quality and lightly cold-working the hole (?)] when the pin is pushed/pressed into position. HT Collars are also designed to facilitate tight-seating of the fasteners [heads] in-position even with the forces of interference in-play.

Hi-Lite [HLT] pins, on the other-hand are an evolution/merging of HL Pin and HT pin designs... and redesigned aspects for the collars. HLT pins are essentially HL pins with a rounded [not bulged-rounded] shank-to-thread transition edge... so it smoothly and 'non-abusively' installs in interference fits. Further, HLT pin/collar internal/external threads and internal depressions/cut-outs are designed to reduce mass in –combinations with higher strength alloys. HLT pins/collars are match-re-sized in various aspects to allow for significant mass reductions in the installed combinations...with very good installed strength and durability.

NOTE: these are the 'Reader's Digest' version' of HL, HT and HLT pin/collar evolution/technology.


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]