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Posted: 10/31/2005 6:32:26 AM EDT
| I have a 3/8 drive torque wrench, very nice one. I believe the opening on the barrel wrenches are 1/2". Can I just get an adapter for this and expect it to work out right? Also a side note, I didn't pay for the wrench is why I would rather get an adapter if possible. Thanks for replies. |
| Yes, you can just adapt it. Make sure you look to see whether it is in inch lbs or ftlbs and convert accordingly. Is it a clicker or needle type wrench? FYI, clicker type are good for setting a bolt/nut to a certain torque and thats it. A needle type is good for setting preload on bearings and such as is used on setting up rear differentials. Not sure what the pertenance of that was but, there you have it. |
| That should work fine. I assume you are torqing a barrel nut? I don't think exact accuracy is that big of a deal. From everything I have read, min is 30 ft lbs and max is 80ft lbs (big range). What is nice about the needle type is after you've toqued the nut, when you further tighten the nut to align the gas tube you will know exactly what you torqued it to rather than just whether or not you reached 80 ft lbs. |
| If it is a direct adapter, the change is negligable. If you can guarantee the adapter won't twist, there will be none. You will lose way more accuracy attaching the torque wrench to the the armorers wrench as it creates a lever. Using a crows foot would be an issue. |
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Yes, you can use a 3/8-1/2 adapter. Best is a beam type torque wrench for this purpose. A "click" type is not really that useful. All you really need the torque wrench for is to make sure you have it at least to the minimum required torque, which is really 31 ft-lb. Really, 25 ft-lb is enough, but 31 is the recommended minimum. Personally, if one lined up at 27 or 28, I'd leave it right there. You must have the threads lubricated, or any torque reading is meaningless. The recommended lube is moly grease... this is ordinary wheel bearing grease with moly disulfide in it. It is dark brown or dark gray in color. If you don't have this grease, plain old grease as you would use in a grease gun is just fine. Do not use Neverseize or similar (that silver or copper colored goop). It has metal particles that are gritty, and become embedded in the aluminum threads. This stuff is made for steel on steel, not our AR's. While tightening the barrel nut, it is important to hold the wrench so that the teeth or prongs are fully engaged with the teeth of the barrel nut. Otherwise it can slip and damage the teeth. Once you reach the minimum torque, take off the torque wrench, replace it with a breaker bar. After you get to that minimum, you don't need to know what the torque is, you just need to get it aligned. Advance the nut until the notch is aligned for the gas tube to pass through. You can make a tool from a piece of drill rod, or a 3" piece of an old gas tube. The rod should pass through the notch, the opening in the weld spring (delta spring), snap ring, and into the receiver. As you approach alignment, the gap in the snap ring and weld spring might be way around on the wrong side. Use a small screwdriver or something to slide the gaps around to the top side. Now try your piece of rod or gas tube. It should line up straight with the bore line, and have equal play to each side. You will need to pull the piece of rod firmly side to side to get the snap ring and weld spring to slip and realign on the barrel nut. You should get to this aligned nut position only by tightening the nut, you should not back off. There is NO magic torque figure where it all lines up. That just does not happen. It might be 31 ft-lb, it might be 60 or 70 ft-lb. Usually it falls in the 40-60 ft-lb range. If you are tightening and can't quite get to alignment, simply back off and tighten a few times. This will smooth the threads and they will "give" just a little, and allow the nut to advance a little more. You may have to do this 3 or 4 times, but it will align. To do all of this you MUST have a solidly mounted strong vise. If the vise is moving, you will have problems if it takes a lot of muscle to align. But seriously, you don't really need a torque wrench. If you have any experience with tools and nuts and bolts, you know when something is loose and when it is tight. You can feel when it starts to tighten up and will not advance much farther. Just get it tight and aligned. I have not used a torque wrench for barrel work in many years. |
| Tweak, I take it you snug it up 3-4 times and then tighten to the next hole? That is how i did my first barrel install and it worked fine. I was able to get a decent torque wrench for free so I figured what the hell, better safe than sorry.At least I have one more tool in my bag of tricks. |
Tweak, why you gotta bring that pick up? I’m trying to put that part of my AR building history in the past!!! 
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That’s how I install my barrels. But if you wanted to use a torque wrench a 3/8 to ½ adapter will not change your torque applied. Where you get into changing torques is when you install adapters extending the arm of the torque wrench. Here is a link with a calculator used for converting torques. This is the basic formula we use in aviation where setting an exact torque is very critical. www.norbar.com/torquewrenchextensioncalculator.php |
I used a torque wrench for awhile to get the feel of the min max settings. Yep, tighten a couple of times, run the nut up see how it lines up, loosen if it's too far out, repeat until it lines up. Haven't bent a nut (on install) in many years.
as a warning to others brother, as warning to others. it was never so much the bent teeth that bugged me as it was the dings in the handguard retainer, I hated having to fix those.
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