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Posted: 1/9/2021 11:24:44 AM EST
I was following the instructions to install a Coda Evolution Lightning Carbon Fiber Handguard - Super Lightweight 15" rail and the barrel nut broke.

The barrel is a Proof Research 16" Carbon Fiber and the Upper is a VLTOR MUR-1A. I greased the threads with aeroshell, hand tightened the barrel nut and then set the torque wrench to 36 ft.-pounds. The barrel nut came apart before reaching 36 ft. pounds.

Coda Evolution is mailing me a new barrel nut but I'd like to know why the first barrel nut failed. I'm a pretty 'handy' guy not really used to parts just breaking during installation.

Ideas?

I used a 1 1/4" crows foot wrench, a 3/8" to 1/2" adapter, and a standard 3/8" torque wrench.



Link Posted: 1/9/2021 12:16:35 PM EST
I'm not being a smartass - did you ask the folks at Coda what could have happened?
Link Posted: 1/9/2021 12:26:26 PM EST
Looks like it cracked along the threads, I'd bet it was machined too thin and when threaded, there was almost no material left. That is a very unusual break, over torquing usually results in a longitudinal crack, not one that goes around the circumference.
Link Posted: 1/9/2021 4:53:11 PM EST
LTTG, I know you're not trying to be a smart-ass.

I emailed Coda Support multiple times and called them multiple times and left a voicemail.

They have not responded to any of my messages BUT they did mail me the new nut indicating things must just be crazy there right now.

Weird, huh?
Link Posted: 1/10/2021 9:44:02 AM EST
Didn't have an issue with the one I installed, but I found that when installing the trunnion it was a really tight fit which is good.  Do yourself a favor and paint the heads of the tiny handguard screws prior to install as they rust easily.  I stuffed the threads into some cardboard, stuck an allen wrench into the socket and sprayed them then immediately removed the wrench while the paint was wet.
Link Posted: 1/10/2021 11:00:08 PM EST
dumb question but why would they rust easily?
Link Posted: 1/12/2021 7:23:21 AM EST
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Originally Posted By atek3:
dumb question but why would they rust easily?
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Thin oxide finished I would guess and my high ph sweat, regardless mine started to rust pretty damn quick so to put an end to it I shot them with some Aluma-hyde I had in the cabinet.
Link Posted: 1/12/2021 11:32:15 AM EST
I'm sure they are VERY busy these days as most any firearm related companies are. Phones ringing off the hook, emails flooding in and they are just trying to keep up.

I imagine it's just a manufacturer's defect in the part itself. I wouldn't worry and carry on with the new part. I wouldn't fault them from not replying and a BIG + for just sending the new part without a single question. * * * * * 5 stars for service & warranty.
Link Posted: 1/12/2021 5:32:25 PM EST
The torque wrench might have lost calibration, so that more torque was applied than desired.

Link Posted: 1/13/2021 10:29:05 AM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By check-raiser:
The torque wrench might have lost calibration, so that more torque was applied than desired.

View Quote


Out of calibration enough torque to crack a steel barrel nut?  If it was that far out of cal it would have busted the aluminum receiver long before the nut.  It was cracked some where in the manufacturing process.  Either during tooling or heat treating.  I'm sure they are not X-raying every nut.  Micro fracture that made it through the screening process.  

On a side note.  I'm glad the company made it right by sending you a new nut.  When your trying to keep prices down thing like this slip through the cracks.  No pun intended.  Let me tell you nothing is free in the manufacturing process.  Inconvenient yes, but they made it right all is good!
Link Posted: 1/13/2021 8:50:43 PM EST
is there any way to test the calibration on a torque wrench?

I tightened it to 25 ft-lbs, then loosened it, then re-tightened it to 25 ft-lbs, then loosened it, then re-tightened it to 35 ft-lbs. 25 ft-lbs felt like... 25 ft-lbs and 35 ft-lbs felt like about 10 ft-lbs more :)

I don't think I cranked it that hard.
Link Posted: 1/13/2021 9:57:11 PM EST
I wonder how many gucci gun parts are operating right on the very edge of durability.
Link Posted: 1/14/2021 2:45:39 PM EST
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By atek3:
is there any way to test the calibration on a torque wrench?

I tightened it to 25 ft-lbs, then loosened it, then re-tightened it to 25 ft-lbs, then loosened it, then re-tightened it to 35 ft-lbs. 25 ft-lbs felt like... 25 ft-lbs and 35 ft-lbs felt like about 10 ft-lbs more :)

I don't think I cranked it that hard.
View Quote

There are 2 easy approaches to checking torque wrench calibration.  Best bet is to send it for calibration, but these will get you in the ballpark.  Serious torque calibration gear costs serious money.

Home calibration check - easy to do at lower torque ratings, can be a pain at higher torques.  This can be relatively accurate at the range tested.
https://www.wikihow.com/Calibrate-a-Torque-Wrench
https://thewrenchfinder.com/how-to-calibrate-a-torque-wrench/

Digital torque adapter - this lets you use a regular wrench as a torque wrench.  They can be a bit pricey for checking a single wrench, and results can be hit or miss.  Read the Amazon reviews on digital torque adapters to get a feel for them if you want to go this way.  I don't know anything about the site below, but they overview some of the available gizmos.
https://torquewrenchcenter.com/best-digital-torque-adapter/
Link Posted: 1/15/2021 7:16:48 PM EST
[Last Edit: 1/15/2021 7:17:24 PM EST by LastRites]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By LarMoeCur:


Out of calibration enough torque to crack a steel barrel nut?  If it was that far out of cal it would have busted the aluminum receiver long before the nut.  It was cracked some where in the manufacturing process.  Either during tooling or heat treating.  I'm sure they are not X-raying every nut.  Micro fracture that made it through the screening process.  

On a side note.  I'm glad the company made it right by sending you a new nut.  When your trying to keep prices down thing like this slip through the cracks.  No pun intended.  Let me tell you nothing is free in the manufacturing process.  Inconvenient yes, but they made it right all is good!
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Discussion ForumsJump to Quoted PostQuote History
Originally Posted By LarMoeCur:
Originally Posted By check-raiser:
The torque wrench might have lost calibration, so that more torque was applied than desired.



Out of calibration enough torque to crack a steel barrel nut?  If it was that far out of cal it would have busted the aluminum receiver long before the nut.  It was cracked some where in the manufacturing process.  Either during tooling or heat treating.  I'm sure they are not X-raying every nut.  Micro fracture that made it through the screening process.  

On a side note.  I'm glad the company made it right by sending you a new nut.  When your trying to keep prices down thing like this slip through the cracks.  No pun intended.  Let me tell you nothing is free in the manufacturing process.  Inconvenient yes, but they made it right all is good!
The coda nut is aluminum not steel.
Link Posted: 1/16/2021 7:23:07 PM EST
Link Posted: 1/23/2021 5:16:26 AM EST
When using any type of extension on a torque wrench it changes the torque
Link to calculate https://www.tekton.com/how-to-accurately-use-a-torque-wrench-with-a-crowfoot-wrench
It is easiest to keep the pivot points in line with each other and measure from those for your calculation. Hope this helps
Link Posted: 1/23/2021 11:45:35 AM EST
[Last Edit: 1/23/2021 11:48:27 AM EST by ahrion]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By bfoosh06:



This... "Mounting System components are made from Aircraft Grade, 7075 -T6 Aluminum, with MIL-A-8625 Type III Hard Coat Anodization."

I have broken a Aluminum barrel nut before... it is very disheartening to hear that "Ting" noise from the aluminum breaking... I now have spares on hand for my aluminum barrel nuts.
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Only aluminum that I would use for a barrel nut would be 7068 tennalum that V7 sells. It's almost as strong as Titanium G5. 7075 and 6061 should not be used as barrel nuts.

Also, to get a proper torque for an extension with a torque wrench that you showed, the wrench needs to be 90° from the extension/adapter. This is, obviously, if the adapter isn't just a straight 1/2 socket, which will yield correct torque. 90° converts perfectly using a barrel nut wrench and ft lbs torque wrench at 90°. No math is needed.
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