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On torque wrenches...

Discussion in 'Gunsmithing and Repairs' started by Slater, Oct 26, 2020.

  1. Slater

    Slater Member

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    Many years ago I was told that, for the best accuracy, avoid using the bottom 10% and top 10% of a torque wrench. With modern technology, does that still apply?
     
  2. WestKentucky

    WestKentucky Member

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    Really depends upon the technology being used. Old school clicker wrenches with springs are still the same technology that they have always been. Newer wrenches with other methods of determining applied force (load sensors and similar) are likely more accurate, but do have limitations. I can’t imagine having a need that clicker torque wrenches or other pretty basic wrenches will not handle with more than enough accuracy. What are you trying to do that requires such accurate tools?
     
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  3. Slater

    Slater Member

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    Just for general firearms use. Doesn't everyone want reasonably accurate torques? I think the average variance is something like +/- 2 inch pounds, which is probably good enough for most applications.
     
  4. Mars5l

    Mars5l Member

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    If the variance is - or + 2 inch lbs id say thats a damn accurate wrench. Im a mechanic and even the higher dollar ones off the trucks are rated to + or - 3%-4%
     
  5. danez71

    danez71 Member

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    Check the spec if you can.

    In my experience, depending on brand/quality, the spec may say something like +/- 3% or 5% in the middle 80% of the range.

    Thats why ppl say that about the upper and lower 10%.
     
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  6. jmorris

    jmorris Member

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    Repeatability is likely more important for things being taken apart and reassembled than hitting torque to the exact in/lb. I use tools like the roto-torq and wheeler set with a good wrench.


    [​IMG]
     
  7. edwardware

    edwardware Member

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    What modern technology? Do you have a magnetic restoration strain gauge wrench?

    So far as I'm aware, every torque wrench on the market uses an iron age flexible beam, 100+ year old mechanical linkage, or a 50+ year old variable resistance strain gauge. Maybe quality and consistency has improved, and price has certainly fallen, but there's no new tech I'm aware of.
     
  8. 12Bravo20

    12Bravo20 Member

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    I agree with jmorris, repeatability is just as important as overall accuracy. I use the Wheeler Fat Wrench all the time for torquing down action screws on my rimfire rifles and on scope rings and other optics.
     
  9. Double_J

    Double_J Member

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    Snap On states to use 21% or greater of the wrenches rated range. If you use the bottom 20% there is a higher likelihood of a wrong reading. this means use the smallest wrench you can get away with. I.e. use a 15-85 inch pound wrench for 32 to 85 inch pounds to stay above the bottom 20%.
     
  10. Slater

    Slater Member

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    Hopefully better than they used to make them. When I was in the Air Force (this was 25 years ago), our shop took delivery of five brand new torque wrenches. We took them in for initial calibration and three out of five were rejects right off the bat. So yeah , that "magnetic strain gauge" thingy can't be any worse.
     
  11. alfsauve

    alfsauve Member

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    I thought it had always been a rule of thumb with all test equipment (measuring equipment) to try and stay within the middle third of it's range. Granted my experience is mostly with electronic measuring and it dates back to moving coil analog meters. Exceptions abound, YMMV.
     
  12. SGW Gunsmith

    SGW Gunsmith Member

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    I have and use a torque wrench, but only for specific needs that require it. If you look to see any of the suggested recommendations for sight and scope base screws on the web, as far as inch-pounds, you'll get more confused than any help.
    For the last several years I'll forgo using any of the slotted or hex-socket screws provided with bases and rings and then use Torx style screws, cleaned of any residual oil and then a drop or two of serviceable Loctite #242. Snug up those screws with a better fitting torx wrench of the correct size and any worries will go away:

    sIYtlt2l.jpg

    This is used for action screws and bolt stock screws, at the ratings suggested for same.
     
  13. Project355

    Project355 Member

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    Just from the engineering viewpoint, the beam torque wrenches are most accurate, but.... in smaller sizes, the spring/click wrenches are the tool of the day. Problem is they're susceptible to dirt/debris/contamination and lube. The flex/beam are more accurate if the scale plate is calibrated correctly.
     
  14. Slater

    Slater Member

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    The only problem I've encountered with beam-type wrenches is that they're often impractical if the fastener you have to torque is in an awkward or hard-to-get-to location.
     
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  15. Howland937

    Howland937 Member

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    I currently own 7 different torque wrenches. 2 are old $30 beam type, a ft/lb and an in/lb.
    3 are clicker type and 2 are the programmable kind that do in/lb, ft/lb, nM, and angle. 4 of them are 1/2" drive and all 4 have 50-150 ft/lb in their working range (one is 15-150, 25-150, 50-250, 50-250). I've checked them against each other in 10lb increments and there's no variation from one end to the other. Of course they could all be wrong...

    Tighten it til it breaks, then back it off half a turn.
     
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  16. Jackrabbit1957

    Jackrabbit1957 Member

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    I work in the aircraft industry, we have our precision tools calibrated once a year, I believe the tolerance is around 2 %. I could be wrong but that's what comes to mind. Dial and clicker types do require it, beam type not so much. However I took a giant step backwards and replaced my clickers with beam style wrenches to get away from all the BS and the company still wanted to cal the beam type. Go figure.
     
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  17. David Hoback

    David Hoback Member

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    I spent many years as professional Master Automotive tech. My tools were all Snap On, Matco. Only kept a few of my super expensive tools...I’ve being the Snap on 1/4” drive torque wrench. Thing is...when I buy a hand tool now, I buy cheap! Harbor Freight usually. Like my HF 1/2” torque wrench. I’ve checked & compared as much as I could over the years...from my professional life to now. I never found anything drastically off about the high/low end measurements. And the el-cheap torque wrenches I’ve tested measured acceptable and to mmh es exactly as my really expensive Snap On torque wrenches.

    While I do agree that we want torque values to be consistent....reality is that NOTHING I torque requires any greater precision than the 3-5% that a CHEAP wrench will deliver.
     
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  18. Jackrabbit1957

    Jackrabbit1957 Member

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    I used a Harbor Freight 1\4 drive torque wrench for about 11years, last time it went for calibration I was told it was too cheap to calibrate, it had been calibrated 10 times by a different company. What really irritated me was it was not their call to scrap it, it's my decision on whether or not to spend the money to cal it. I went to beam types after that.
     
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  19. SGW Gunsmith

    SGW Gunsmith Member

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    I'm with you, it's your property and they had no business scrapping it WITHOUT your permission.
     
  20. Jackrabbit1957

    Jackrabbit1957 Member

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    Lets see them try that with a beam wrench, theoretically they hold accuracy better than a clicker, but they can be a pain to use.
     
  21. jmorris

    jmorris Member

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    I can't argue the content of what you say. "Drastically" and "acceptable" are qualitative words and no book will tell you to torque to an acceptable amount but don't drastically over torque, why they give a quantitative value.

    I agree that a human with the proper skills can be very repeatable but the transfer of that knowledge can be difficult.

    I guess that's why I can't make things like my Grandmother could, despite having her recipes, a pinch, dab, little, bit and until looks right are not quantitative.
     
  22. earplug

    earplug Member

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    My guess is residual lube on the threaded parts will effect torque readings more then the wrench workings.
    I bought my kid a torque wrench to work on his racing bicycles. One of the better toys you can buy. I still have a old beam wrench .
     
  23. David Hoback

    David Hoback Member

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    Good points. Especially on transfer of knowledge. It’s also quite easy for those of us with a skillset to take some things for granted. What may seem common sense to me, may not to another. Everyone from the automotive world understands the saying “I have a Calibrated elbow”.:)

    Any & every fastener has a torque reference. A torque reference is put in place as the point at which said fastener will not loosen. Obviously too light a setting, the faster may loosen. But what is the danger in over torquing? Well, the initial danger is the faster breaking, becoming damaged or stretching(which will also lead to loosening). And obviously, there is a risk to the object being the fastener is securing. Example: crushing a scope tube by over torquing ring bolts. And then there is the difference of Inch/lb. & Foot/lb. values....Inch/lb. being far more sensitive.

    I spent many, many years using torque values professionally. And something I’ve learned is a crazy expensive torque wrench just isn’t necessary.
     
  24. Double_J

    Double_J Member

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    I remember taking my Harbor Freight torque wrenches over to the cal lab at my old job. It cost me a big Mac combo meal to get them calibrated, and the tech said they were almost spot on. I used the tar out of them for about 12 months and brought them back and they were just a hair out of calibration. The tech told me to keep using them and verify against a standard every 3-6 months. Most things I work on don't have that narrow of a range and I can use the "calibrated elbow" to get it close, but the Harbor Freight wrenches are still there and are inexpensive.
     
  25. jmorris

    jmorris Member

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    I too have been around the automotive world awhile.

    I know some, that when asked to what torque they tightened a fastener they will tell you two "chuga chugas", noting how many times the impact hammered.

    Then there are also torque to yield fasteners that are (supposed to be) one time use as they are stretched when used.

    I have removed lots of broken fasteners over the years because of both reasons.

    Then again, I have seen a few that could never make it to the torque specifications in the book, then your back to feel again.
     
    Blue68f100 likes this.
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