What Torque Wrench Are You Using?

[MistWolf]

The .mil manual specifies a particular tool, yes the math is included.

HOWEVER, this can’t be used as a general statement. Proper use of an adapter is 90* to the torque wrench or do the math.
37 years in aviation

TA x L L + A = TW

It looks like we've both been in aviation for about the same length of time!

So, you know that AC 43.13-1B Para 7-40 and Fig 7.2 covers torque and how to calculate the correct setting when using torque adaptors. However, I could find nothing in Chapter 7 authorizing the use of a torque adaptor set to 90 degrees. If you know where it is, I'd be obliged if you passed along the information.

The beginning of AC 43.13-1B under PURPOSE also says-

The repair data may also be used as approved data, and the AC chapter, page, and paragraph listed in block 8 of FAA form 337 when:
a. the user has determined that it is appropriate to the product being repaired;
b. it is directly applicable to the repair being made; and
c. it is not contrary to manufacturer’s data.

The important part is c. "not contrary to manufacture's data". In the matter of torquing the barrel nut using the barrel nut wrench, the AR manual says to use the barrel nut wrench inline with the torque wrench and set to 30 ft/lbs to start. Do not compensate for the added arm of the barrel nut wrench. This is assuming the use of the correct barrel nut wrench.

(I do realize that setting the torque adaptor to 90 degrees is an acceptable practice IAW with c. as noted above.)

[Hammer_Man]

Does anybody know the measurements of the tool listed in the TM? I’d like to know the distance of the 1/2 drive cut out to the part the interfaces with the barrel nut.

[lysander]

I am more familiar with the military manuals, NAVAIR 01-1-8, and TM 1-1500-204-23-9, both of which, in addition to showing the calculation noted above, gives the formula for the extension at some angle, so that if you find yourself using a 90 degree offset, TW = TA . . . .

Attachment 66518

[lysander]

A = 2 inches

With a standard 18" torque wrench the difference is 10%.

[GH41]

"The important part is c. "not contrary to manufacture's data". In the matter of torquing the barrel nut using the barrel nut wrench, the AR manual says to use the barrel nut wrench inline with the torque wrench and set to 30 ft/lbs to start. Do not compensate for the added arm of the barrel nut wrench. This is assuming the use of the correct barrel nut wrench"

If this is true the manual doesn't say torque to "X" ft/lbs. It says set the wrench to "X" ft/lbs and use the "Y" wrench oriented to inline. It doesn't specify what the barrel nut is actually tightened to but it isn't 30 ft/lbs.

[MistWolf]

"The important part is c. "not contrary to manufacture's data". In the matter of torquing the barrel nut using the barrel nut wrench, the AR manual says to use the barrel nut wrench inline with the torque wrench and set to 30 ft/lbs to start. Do not compensate for the added arm of the barrel nut wrench. This is assuming the use of the correct barrel nut wrench"

If this is true the manual doesn't say torque to "X" ft/lbs. It says set the wrench to "X" ft/lbs and use the "Y" wrench oriented to inline. It doesn't specify what the barrel nut is actually tightened to but it isn't 30 ft/lbs.

That's correct.

[lysander]

"The important part is c. "not contrary to manufacture's data". In the matter of torquing the barrel nut using the barrel nut wrench, the AR manual says to use the barrel nut wrench inline with the torque wrench and set to 30 ft/lbs to start. Do not compensate for the added arm of the barrel nut wrench. This is assuming the use of the correct barrel nut wrench"

If this is true the manual doesn't say torque to "X" ft/lbs. It says set the wrench to "X" ft/lbs and use the "Y" wrench oriented to inline. It doesn't specify what the barrel nut is actually tightened to but it isn't 30 ft/lbs.

But then, just to be contrary about the situation Drawing numbers 8448522 - Upper Receiver and Barrel Assembly (M16A1), 9349050 - Upper Receiver and Barrel Assembly (M16A2), 12972680 - Upper Receiver and Barrel Assembly, and 12997148 - Upper Receiver and Barrel Assembly (Heavy Variant), all have the same note on barrel installation (see below). This note does not specify a tool and states simply that the nut is to be torqued to 30 to 80 ft-lbs.



So, the manufacturer's drawings and the manuals (this goes back all the way to the TM 9-1005-249-23 & P) have disagreed on the actual torque for the barrel nut (and flash suppressor, and receiver extension btw) for at least the last 45 years. The fact they have never bothered to consolidate the two tells me: It ain't that big a deal.

Also, you will note the "correct" lubricant for the threads is Dow Corning Molykote G, which actually is an anti-seize compound, not a GP grease, like MIL-G-21164 (aka Aeroshell 33MS), so the " . . . or equivalent . . . " covers a lot of ground.

Track #2, of Weird Al Yankovic's "Bad Hair Day" Album.

[MistWolf]

But then, just to be contrary about the situation Drawing numbers 8448522 - Upper Receiver and Barrel Assembly (M16A1), 9349050 - Upper Receiver and Barrel Assembly (M16A2), 12972680 - Upper Receiver and Barrel Assembly, and 12997148 - Upper Receiver and Barrel Assembly (Heavy Variant), all have the same note on barrel installation (see below). This note does not specify a tool and states simply that the nut is to be torqued to 30 to 80 ft-lbs.



So, the manufacturer's drawings and the manuals (this goes back all the way to the TM 9-1005-249-23 & P) have disagreed on the actual torque for the barrel nut (and flash suppressor, and receiver extension btw) for at least the last 45 years. The fact they have never bothered to consolidate the two tells me: It ain't that big a deal.

Also, you will note the "correct" lubricant for the threads is Dow Corning Molykote G, which actually is an anti-seize compound, not a GP grease, like MIL-G-21164 (aka Aeroshell 33MS), so the " . . . or equivalent . . . " covers a lot of ground.

Track #2, of Weird Al Yankovic's "Bad Hair Day" Album.

LOL! If there wasn't conflicting data, the guy on floor would wonder if he got the right blueprint.

However, that's not the complete print. Assembly prints normally include notes for how certain processing are performed including torque.

[lysander]

However, that's not the complete print. Assembly prints normally include notes for how certain processing are performed including torque.

Yes, that is not the complete drawing, there are the other two pages of that drawing, the parts list, the assembly equipment list, the inspection equipment list, and the quality assurance provisions, but what you see above is how the torque specified.

Now, here's the problem:

As you and hk_shootr have gone to establish the torque correction equation given an extension, you will have noted that the correction calculation involves both the extension length [A] and the torque wrench length [LL].

The torque wrench specified in the manual (TM 9-1005-319-23 & P) comes in two flavors, one the torque wrench in "Shop Set, Small Arms: Field Maintenance, Basic, Less Power", P/N SC4933-95-A11 (NSN 4933-00-754-0664), and Torque Wrench, ft-lbs, P/N A-A-411 (NSN 5120-00-640-6365). Neither of these torque wrenches part numbers are a specific brand or model torque wrench but are a description of a commonly found commercial item, and mainly deals with the accuracy and repeatability requirements. The one thing that is specifically not stated is the overall dimensions of the wrench, so the length of the wrench is anywhere from 17-1/2" to 24".

The different lengths of the acceptable types of torque wrench in the manual gives a +/-5% variation on applied torque.

This is why when you make assembly drawings you put the actual torque down not the indicated torque for the collection of tooling assemblies. Because that one specified piece of tooling with break and somebody will have to figure out to do the job with non-specified tools, or somebody will change the design of the specified tool without telling you and for a year everything will be built wrong, until you find out.

[Failure2Stop]

30ft/lbs minimum with the tool in line with the torque wrench is still below where most would want a barrel nut, so being 90 degrees off or inline really doesn't mean anything, ESPECIALLY because that barrel nut needs to be advanced to get the gas tube through the teeth gaps on a TDP M4/M16, and 80ft/lbs even with the wrench inline is safely below the "actual" limit of a good receiver and barrel nut.
Also remember that the US Army mislabeled both the gas key screw torque and the "castle nut" torque at one point, so that manual should be considered "reference" more than anything else.