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Deflecting beam torque wrenches

Discussion in 'Technical and Troubleshooting Torque' started by vahramh, Dec 5, 2015.

  1. I have started suspecting that I may have been using my "precision" torque wrench wrong all this time :)

    When setting the torque, should the end of the trapezium bar be aligned with the required torque, or the end of the bolt attached to it? So in the attached picture is the torque set to 10 Nm or 6 Nm? 20151205_150615.
  2. What is the function of the "bolt"? Is it a fine adjustment for the position of the metal wedge? It is a REAL good idea to check the calibration of any torque wrench to confirm that it is actually accurate by measuring a known load against the scale. This can be done with an accurate spring scale if you can find one. It is possible to use almost any accurate scale if you can figure out how to apply load to the wrench. If you can do this, then you'll know which it is. On the face of it, I would say 6.

    The nice thing about this type of torque wrench is that they can be adjusted, and should be "dialled in" (checked and adjusted) prior to use, as assembly is no guarantee of accuracy, and they are easily adjusted or maladjusted. That's what the bolt might be for. If when you turn the bolt, the ramp moves, then it is your fine adjustment for accuracy. I've always read the back (flat) end of the wedge.

    I am intrigued by the units (In lbs?) Foot pounds is the (old) common imperial measurement. Newton Metres, while politically correct does not equate to almost any other thing that people measure, but they do have the ability to measure kilograms

    For your reference 10 Newton metres = 7.376 Ft. lbs (foot pounds) or 1.02 kg metres That is, force applied as weight at distance. 7.376 pounds at one foot distance or 1.02 kg applied at 1 metre.

    There can be a lot of buggerizing around to establish accuracy, but if you can find someone with a known accurate one, you can turn them against one another to check and adjust - it will take a double sided half inch drive - a half inch socket in a a short extension will do to link them. It's very comforting to know something is actually measuring what it does with accuracy.
  3. You have it set for 10 Nm Looks like a Warren & Brown, very nice tool
  4. Definitely set to 10Nm. You probably know to push the little metal rod in when you torque a bolt. When it clicks, stop tightening
  5. I stand corrected
  6. Thanks guys,

    I have been aligning the edge of the bar with the required torque since I bought it 2 years ago. Until yesterday. I started explaining the principle of torque wrench operation to my daughter. Then I told her that these needed to be re-calibrated regularly, and she asked - "how do you calibrate it?" I went numb... The only movable part that can be used for calibration is the bolt :(

    So there we go - you guys just confirmed my worst fears. I paid quite a bit for it (pretty sure it was over $250), and never used it correctly! And now there are a few bolts around that have been over-torqued.
  7. To calibrate a torque wrench you need another torque wrench to compare to, that is known to be correct. Lots of places can do it for you
  8. Yeah, definitely set to 10Nm. I was fortunate enough when I did my apprenticehip to have to build one of these, I used it heaps until it got lost in a fire in my fathers shed.
  9. Is a deflecting beam type of torque wrench even going to need calibrating?

    You are relying on the flex built into the tool to set off the little click, so I would have thought that barring absolute abuse or missuse of the tool, there is nothing that can wear or change it from when it leaves the factory, unlike the ratchet style of wrench.

    Pretty fool proof I would have thought.....providing you don't try to anneal or temper it and remember to push the button in.
  10. Mine is identical to this and is a Sidchrome........which I believe is made by Warren & Brown! :wacky:
    • Agree Agree x 1
  11. Using the tool to undo nuts in the opposite direction is very big no no.
    Also going past your setting to give it a bit extra is not on.
  12. This is why I went stahlwille instead of Warren brown.
  13. Temperature perhaps..... Cr steel elasticity varies about 3% over normal ambient temperature range.

    About all I can think of is wear to joints causing minor changes over time.... But I'm pretty sure they only certify them for a period of time cause they don't want to be responsible for them forever when people may abuse them.
  14. FAQ - Warren & Brown Precision Tools
    When will I need to recalibrate my torque wrench?
    Depending on usage, generally every 12 months or 10,000 cycles. We frequently see 20 year old torque wrenches that are still accurate.
  15. Both of these issues require the user be recalibrated, rather than the tool itself I would have thought.
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