Rule of Thumb for Remaining Wall Thickness on Threaded Insert Repair

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Jetmxmanager Member Join Date: Jan 2008 Posts: 8	Rule of Thumb for Remaining Wall Thickness on Threaded Insert Repair 01/14/2008 10:04 AM
	In the aviation industry, we're heavily regulated by OEM & Federal "Acceptable Methods, Techniques and Practices". As such, I'd be interested in your input on the following hypothetical repair: Problem: Pulled Threads in Aluminum Housing (2024-T4) Proposed Repair: Threaded Insert (Heli-Coil) Repair Dimensions: Remaining wall thickness after tapping for Heli-Coil = 0.070". Per the OEM standard practice governing maintenance on this unit, the proposed repair would be considered unacceptable since the remaining wall thickness would fall below the 0.090" min requirement. Based on experience in your respective industries, would you be able to proceed with this repair? Thanks in advance for your input.
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Kwetz Guru Join Date: Oct 2007 Location: Madrid, Spain Posts: 716 Good Answers: 25	#1 Re: Rule of Thumb for Remaining Wall Thickness on Threaded Insert Repair 01/15/2008 2:38 AM
	Hi, In all industries we all have some types of regulations, standards, etc. to follow. It is supposed that people who issued the requirements took into account all the design considerations (including "safety factors"). So, if you try to change any limitation, you must know all considerations the designers had in mind and evaluate the decission at your own risk. In other words, I only would change a requirement if I know perfectly all design conditions (ambient, load cases, etc) and after the corresponding evaluation. My recommendation: Don't accept that repair. __________________ It's stupid to discuss about AI: We´ve reached by the "B" way. We' ve producing men as clever as machines.
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Abdel Halim Galala Guru Join Date: Feb 2007 Location: Cairo, Egypt Posts: 1733 Good Answers: 246	#2 Re: Rule of Thumb for Remaining Wall Thickness on Threaded Insert Repair 01/15/2008 5:09 AM
	Per code OEM & Federal "Acceptance Methods, Techniques and Practices", this repair is not accepted. Otherwise, you can proceed a stress analysis to find the stresses through that part of reduced wall thickness, and compared with the accepted stress figures. __________________ It is better to be defeated on principles, than to win on lies!
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Jetmxmanager Member Join Date: Jan 2008 Posts: 8	#3 Re: Rule of Thumb for Remaining Wall Thickness on Threaded Insert Repair 01/15/2008 9:14 AM
	To ask another way, what "rule of thumb" exists in other industries use for remaining wall thickness? The standard we generally work to falls between 0.070"-0.090". I was just curious as to what "standards" others may be using. (More of a general question) Thanks for the input.
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Keith E Bowers Power-User Join Date: Jan 2007 Location: Houston,Texas Posts: 378 Good Answers: 24	#4 Re: Rule of Thumb for Remaining Wall Thickness on Threaded Insert Repair 01/15/2008 12:05 PM
	You would have to have the OEM/PMA manufacturer review the proposed repair, do whatever analysis THEY require in order to accept the proposed repair. YOU can legally ONLY conform to the presently acceptable repair tolerances. Any deviation MUST be sanctioned in writing by the OEM/PMA manufacturer. __________________ Keith E Bowers, PMP
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BlueAussieBoy Power-User Join Date: Sep 2006 Posts: 451 Good Answers: 16	#5 Re: Rule of Thumb for Remaining Wall Thickness on Threaded Insert Repair 01/16/2008 7:11 PM
	I have dealt with cases where the wall thickness for a thread was inadequate by adding additional weld metal to outside of a flange to a metallurgist's requirements. This was followed by a full heat treatment. Is this the sort of information you are interested in? __________________ Make it so.
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Pineapple Power-User Join Date: Jan 2008 Location: Toronto, Canada Posts: 302 Good Answers: 4	#6 Re: Rule of Thumb for Remaining Wall Thickness on Threaded Insert Repair 01/17/2008 5:19 PM
	There are many way to repair thread. Helicoil is only one. There are other kind of inserts. You can drill it out and weld a solid piece in then tap it again. You can epoxy the hole then tap it. You can drill the whole thing out and replace with thread rivet or PEM insert. Rule of thumb: If you got a bad feeling about it, don't do it. __________________ Pineapple
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 31078 Good Answers: 826	#7 Re: Rule of Thumb for Remaining Wall Thickness on Threaded Insert Repair 06/16/2023 10:00 AM
	<...unacceptable...> to whom? That is the direction of travel for these sorts of questions, for that is where the liability lays. __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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