Taper-Lok Fasteners

[Garmin]

Hello everyone,

I have just joined the forum and have to say this is a real gold mine of information and help/advice.

I would like to ask a question on Taper-Lok fasteners and hope this is the correct forum to ask it in (as it is aircraft related).

Are Taper-Lok fasteners re-usable fasteners??

That is to ask, after the removal of a Taper-Lok fastener (of which could be of any particular diameter and possibly 1st or 2nd oversize)it is cleaned and visually inspected and found to be "visually serviceable", can this fastener be re-used?
Is there any documentation on this saying they are allowed to be re-used or is it that because they are an interference fit fasteners upon removal they are scrapped.

I hope someone can be able to spread some light onto this point and a definitive answer can be sourced.

Thanks and Regards in Advance

Garmin

 

[Stache]

In short taper locks are not re-useable. It has been my experience removing taper locks will damage them. In most cases the taper lock is drilled down the center to relieve the stress. When a punch is placed in the drilled hole and hit with a hammer the taper lock will collapse on itself not damaging the hole. This is one way to remove taper locks the other way is to use a brass drift and try driving the taper lock out.

In all cases the taper lock hole will have to be reamed to clean it up and the next over size installed. I don’t have all my books with me to reference right now, but will look some up when I can.

Stache

 

[FastMouse]

I fully agree with Stache.

I used to be involved in aircraft repair design & analysis, and we NEVER reused TaperLoks. No exceptions.

The hole was always reamed out to some oversize to remove the damage in the bore of the hole caused by removal of the TaperLok.

FastMouse

 

[Garmin]

Thank you Stache and FastMouse for your replies,
Very much appreachiated.

This topic is very interesting as I here both yse and no answers.

I fully understand and agree that in many cases the actual removal of the tapre-Lok may render the fastener unserviceable.
We have an inspection that requires the removal of Taper-lok fasteners and after to reinstall the if the hole condition is to specified conditions and the fastener is serviceable. The original fastner was stated as being used again.

Having researched around I have also found that the Boeing SRM for the B747-100/-200/-300 in Chapter 51-30-02 Para 11 that Taper-Lok fasteners can be used again if they are relubricated. The full process of relubricating is laid out as well as the lubricant and solvents.

Looking over at the A330 SRM Chapter 51-42-11 Para 9F it states after you examine the bolt, if condition is satisfactory, it can be used again but to be relubricated. Para 4B gives the relubrication process and Chapter 51-35-00 Para D gives the Lubricant and Cleaning Solvents.

So it seems it is really is a topic that can be argued for both sides.
I got an email from SPS Technologies (Taper-Lok distributer) and the gentleman states similar reasons as yourselves as well as stating that some coldwork stress from the installation will be lost.

I would really be interested in hearing /seeing any other information to support or reject the point of re-use.

Thanks again.

Garmin

 

[FastMouse]

That's interesting. Most of my experience is on Airbus, although predominantly on ATA 57. I was unaware of reusing TaperLoks in ATA 51. The history of Airbus means that it is sometimes possible to find different approaches taken for different ATAs. On 57, we were more than aware of the difficulty and cost of procuring 1st and 2nd oversize TaperLoks, but this was one issue that we stood firm on and reinstalling the TaperLoks didn't happen in the jobs I was involved in for all the previously mentioned reasons. However, since my involvement, there has been activity in areas with a lot of TaperLoks and perhaps some work has been done to reassess the approach. Without doing some digging I can only repeat my experience: we never reinstalled TaperLoks in the jobs I was involved with. On the other hand, if it does not contravene the SRM for your structural area, then there does seem to be scope to reuse the fastener... but if it is beyond what the SRM allows, you're on your own!

As an aside, Stache was discussing TaperLok removal. In my experience, the people doing the actual work on the aircraft would sometimes drill into the TaperLok shank from the head and thread the hole. They would make up a collar that stood over the head of the TaperLok, but rested on the skin. A threaded bolt would be inserted into the threaded hole, with the head of the bolt supported on the collar. The bolt would the torqued and, with some effort, the TaperLok would be pulled out of the hole. Neat! I can't recall if that was just for larger diameters, but it was documented in the SRM.

Good luck and may the numbers work in your favor.

FastMouse

 

[Garmin]

FastMouse,

Thanks for your reply.
I have a background of both military and civil and the airline I was with just before had the same process of not re-using the taper-lok fasteners.
It has also been my experience and practice that we never re-used the taper-lok fasteners after use.
After going thru a copy of the CD SRM of the 747 Classic and the A330 and found that it actually allowed re-use (as I briefly put in the post before). This even surprised me.

I have been tasked with a project to find out what is available datawise on the re-use of the Taper-Lok fasteners as the aircraft we are supporting has issues with the availabity of some of the normal (and especially oversize) part numbers and this needs to be addressed to be able to give support till life of type.

Thanks again and Cheers
Garmin

 

[leeconner]

Are these taperloks hard to find? Assuming availability to be an issue, here are the Rules for their re-use, as I understand them. Part 43 performance rules say I must use aeronautical parts and acceptable practices in preventive and routine maintenance, as well as alterations and repairs not defined by Part 1.1 or Part 43 App A as Major. The parts I can use without further FAA Approval are defined in AC 20-62D and Part 21.3xx. IF you can qualify the removed taperloks to Part 21 criteria, you know the source of the parts you are installing, so you are good to go!
Now, second, if you have Approved data (is the SRM FAA Approved?)for removal, inspection of the fastener and the hole and then reinstallation, I see no reason to question the Approved design, or the Approved SRM that says it can be reinstalled. After all, a properly installed taperlok is not failing in the hole. The replacement of any interference-fit fastener by us old-timers was a good habit not encumbered with availability issues or need to document the data supporting every step of a routine process.

 

[rb1957]

i guess you learm something new everyday.

i would never have thought to reuse an interference-fit fastener, and consider it a dangerous exercise and a false economy.

maybe there's someone at Boeing who can defend their practice ?