Reaming recess in Hi Lok pins?

[Screwman]

Has anyone run into reaming out the hex recess in the tip of Hi Lok pins during installation? We have not installed these before and my boss is worried that he is going to see that as a failure mode.

 

[der8110]

Not an issue. The collar twists of at a torque far lower than the hex recess in the pin would "ream" as you call it. That is - if you are using standard combinations of pins and collars. Theoretically, there could be a 'soft' pin and 'hard' collar combination but those would be outside the recommendations.

 

[kontiki99]

It's been a while since I did any aircraft sheet metal work, but what I recall is that the hex recess should be something you’d rarely use anyway.

Hi-locks are generally an interference fit.

It shouldn’t tend to spin in the hole while the collar is snapped.

When it does spin, you should probably consider re-drilling to the next oversize and try again.

I understood that the act of driving the pin into the slightly undersize hole was to intentionally work harden the inner surface.

 

[der8110]

Hi-Tigue pins are meant to impart residual compressive stresses ("work harden"), the hole tolerances of regular Hi-Loks don't have any (appreciable) effect. Other than, say, more efficient load transfer.

Installers come up with new shortcuts every day, but not using a hex recess is a new one. Shouldn't spin and can't spin are two different things.

 

[OldME]

Interferance fit to hole (bottom limit of spec) will usually eliminate fastener spinning and eliminate requirement to use hex key. If it is a transitional or clearance fit, make sure you use good quality allen keys. (

http://www.fastenertooling.com)

sells keys made from tool steel specifically made for Hi-Lok installation. Aluminum collars are easier to install than steel, make sure you chamfer the head side of the hole to accommodate radius on fastener. Make sure holes are round and true, perpendicular through attachment face. Wet install with primer or sealant if disimilar material protection is a requirement re galvanitic corrosion. Use grip length gauge or spec dimensions to make sure that you don't bottom out collar or have threads in bearing.