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Thread: Friendly reminder...nearly all torque values are in foot pounds...

  1. #41
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    Quote Originally Posted by Iraqgunz View Post
    People actually use a torque wrench for their castle nuts? I always used my common sense and MK 1 MOD 0 arm.
    I think when people first get started, it is important for them to "Feel" how much (or how little) 40 ft lbs actually is. Once you get that experience, a torque wrench is no longer needed (as you can go by feel).




    C4

  2. #42
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    Quote Originally Posted by C4IGrant View Post
    Who uses Armalites armorers manual when building a gun???



    C4
    I don't know. Apparently this guy. He kept informing me that Armalite's manual states 40 inch pounds.

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    olekennyroy thank you sir, I think I will be giving that a try.

  4. #44
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    Quote Originally Posted by a0cake View Post
    I don't know. Apparently this guy. He kept informing me that Armalite's manual states 40 inch pounds.
    Must be the same guy that keeps telling me that if you attend shooting schools, you are a "Mall Ninja."




    C4

  5. #45
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    There are to many variables to just draw a flat line and say here is one and here is the other. It has been a long time since I had any machining training but I know that specs for bolts as small as 1/4" grade 2 are all in foot pounds.

    Plus in/lbs and ft/lbs are the same, in/lbs just makes for smaller discrimination if that makes sense. That being, 6 inch pounds is 1/2 foot pound.

    Not much on a rifle that is going to need an in/lb wrench. 1 ft/lb is a remarkably little amount of force. In/lb screwdrivers commonly have a max setting of 50 in/lb (4+ ft/lbs). That isn't even straining to reach that level with a screwdriver.

    To answer your last question, the fastener grade plays a huge roll as well as diameter. The difference in tensile strength from a grade 2 to a grade 8 is double or more.

    Quote Originally Posted by jmart View Post
    So from an engineering standpoint, what is the demarcation line for when you switch from inch-lbs to ft-lbs? Iis it a function of fastener diameter, and all small screws are always specced in in-lbs, while larger nuts are specced in ft-lbs?

    When I think in-lbs I think fastening split rings on optics, floorplates on BA rifles, etc. But then when we talk installing barrels and receiver extensions, we should always think ft-lbs because of their larger diameters? Or is it a screw threading size issue -- fine threads get in-lbs and coarser threads get ft-lbs?

  6. #46
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    Quote Originally Posted by C4IGrant View Post
    I think when people first get started, it is important for them to "Feel" how much (or how little) 40 ft lbs actually is.
    exactly, the torque values were set in place, in large part, to quantify how tight is tight and how loose is loose across a wide spectrum of assemblers, armorers, and maintenance types. Any part that has a very critical torque tolerance has no business being on a combat gun.

  7. #47
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    Tweak and others who don't measure torque on castle nuts, what you're saying makes a lot of sense. The majority of people who have said they do it by feel are experienced guys and know what they're talking about. So there's obviously merit to what you're saying and it's not a big issue.

    But I've got to ask, what is the downside to doing it by the book (or suggesting to do so) if you've got a torque wrench handy?

    Example: the guy at the range. He obviously has no common sense. He thought 3.3 ft/lb's (40 inch pounds) was enough. Do you trust somebody like that to make a common sense decision on "tight enough?" Simply telling somebody like that to go "12 times tighter" will likely result in stripped threads or a cracked part.

    For this reason, I think my advice to tighten it to 40 foot pounds was solid advice. That's why if / when asked my standard reply is the by the book answer, and that's why there is a by the book answer in the first place.
    Last edited by a0cake; 12-13-11 at 16:41.

  8. #48
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    Also I've got to ask...

    If the exact torque on a receiver extension is not important and the spec is published only to account for variables in people's perception of "tight" then why are there different specs for rifle and carbine extensions?

    Colt says 35-39 ft-lbs for rifles and 38-42 ft-lbs for carbines. It's interesting to note that although the two figures are very close, Colt does in fact make a distinction.

    So, again, if it is not important to be precise, what is the reason for publishing two different but nearly identical sets of torque specs?

    Using your (those who say common sense tight is enough) logic, Colt could have just published the same spec for the carbine as the rifle spec which already existed. They didn't. Why?

    This may be an unanswerable question, or it may have a legit answer. Just food for thought.
    Last edited by a0cake; 12-13-11 at 17:01.

  9. #49
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    Quote Originally Posted by a0cake View Post
    Tweak and others who don't measure torque on castle nuts, what you're saying makes a lot of sense. The majority of people who have said they do it by feel are experienced guys and know what they're talking about. So there's obviously merit to what you're saying and it's not a big issue.

    But I've got to ask, what is the downside to doing it by the book (or suggesting to do so) if you've got a torque wrench handy?

    Example: the guy at the range. He obviously has no common sense. He thought 3.3 ft/lb's (40 inch pounds) was enough. Do you trust somebody like that to make a common sense decision on "tight enough?" Simply telling somebody like that to go "12 times tighter" will likely result in stripped threads or a cracked part.

    For this reason, I think my advice to tighten it to 40 foot pounds was solid advice. That's why if / when asked my standard reply is the by the book answer, and that's why there is a by the book answer in the first place.
    First, it is just fine to follow the manual.

    With that said, some of what is written in it (like for barrel nuts), might not be the best ft lbs numbers for say a DD or LT barrel nut. So in that instance, it is better to follow what the manufacturer states.

    Stayin with a USGI gun for a moment, lets say that you get the barrel nut to align with the gas tube hole, but it is just below the minimum. In order to get to the next slot, you would have to go over the max value called for. This is a poor idea IMHO and you are better off staying just below the spec than going over the max.



    YMMV.



    C4
    Last edited by C4IGrant; 12-13-11 at 22:39.

  10. #50
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    No argument there and that's exactly what I do when it comes to barrel nut torque. My unit is fortunate enough to have small arms repair specialists attached at the unit level...well anyway I've seen one of their newer guys do just what you described. There had to be 150 ft/lbs on that barrel nut easy. Fortunately we caught him in the act...No-Go for sure.

    Quote Originally Posted by C4IGrant View Post
    First, it is just fine to follow the manual.

    With that said, some what is written in it (like for barrel nuts), but not be the best ft lbs numbers for say a DD or LT barrel nut. So in that instance, it is better to follow what the manufacturer states.

    Stayin with a USGI gun for a moment, lets say that you get the barrel nut to align with the gas tube hole, but it is just below the minimum. In order to get to the next slot, you would have to go over the max value called for. This is a poor idea IMHO and you are better off staying just below the spec than going over the max.



    YMMV.



    C4
    Last edited by a0cake; 12-13-11 at 17:18.

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