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DanielBK
Joined: 26 Jul 2007
Posts: 2
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 Posted: Mon Jul 30, 2007 10:35 am Post subject: Re: More torque wrench |
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| ashontz wrote: | Why would it swing down to a near vertical position, it's clamped in the vise. The only movement you'll see is about 1 or 2 degrees as indicated on the torque wrench scale. If you want to get really accurate you could also factor in the 1 or 2 degree movement but it's negligible. ...
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The "near vertical" was, as stated, an imaginary wrench used solely to illustrate an extreme. (It's always easier to envision the extremes & thus the principle at work).
But 1-2° isn't always a realistic condition either. We clamped the stud, not the handle or head of the tool. I have an old bar & poointer type that will swing a good 20° in it's range. I agree that in the lightly loaded condition, the effect is negligible. But then, if it's only swinging 1 or 2 °, I should be using a lighter wrench anyway, as the accuracy at the extremes is usually less than in the midrange.
Someone else noted that this isn't an engine, that torque is measured at the perpindicular in any event. That is the spot on: We either need to measure at the perpindicular or, for all practical purposes, very near to it, or we aren't getting a true torque reading. It's easy enough to do it correctly.
Daniel
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ashontz
Joined: 27 Dec 2006
Posts: 723
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| Posted: Mon Jul 30, 2007 11:31 am Post subject: Re: More torque wrench |
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Actually, the twist/flex across the length of the bar IS the torque being measured at the scale. The stud is where it needs to be clamped. That's just simulating what's going on while using the wrench, except the wrench isn't going around. In fact, by the time you get to your torque setting, particularly if it's high, the wrench isn't moving much anyway at that point.
| DanielBK wrote: | | ashontz wrote: | Why would it swing down to a near vertical position, it's clamped in the vise. The only movement you'll see is about 1 or 2 degrees as indicated on the torque wrench scale. If you want to get really accurate you could also factor in the 1 or 2 degree movement but it's negligible. ...
|
The "near vertical" was, as stated, an imaginary wrench used solely to illustrate an extreme. (It's always easier to envision the extremes & thus the principle at work).
But 1-2° isn't always a realistic condition either. We clamped the stud, not the handle or head of the tool. I have an old bar & poointer type that will swing a good 20° in it's range. I agree that in the lightly loaded condition, the effect is negligible. But then, if it's only swinging 1 or 2 °, I should be using a lighter wrench anyway, as the accuracy at the extremes is usually less than in the midrange.
Someone else noted that this isn't an engine, that torque is measured at the perpindicular in any event. That is the spot on: We either need to measure at the perpindicular or, for all practical purposes, very near to it, or we aren't getting a true torque reading. It's easy enough to do it correctly.
Daniel |
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ashontz
Joined: 27 Dec 2006
Posts: 723
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| Posted: Mon Jul 30, 2007 11:43 am Post subject: Re: More torque wrench |
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| daveaustin2(at)primus.ca wrote: | Are the torque specs so close that it is necessary to go to the extremes you
folks have written of? How about torqueing up bolts that, by definition,
use castle nuts? Do you go up in torque to the next slot, or down to the
previous slot?
Dave Austin 601HDS - 912, Spitfire Mk VIII |
Torqued nuts and bolts aren't supposed to come off on their own because the clamping force due to the torque should exceed the maximum design force the bolt would see longitudinally. For example, head bolts on an engine, the force that the bolts are exerting holding the head to the engine block exceeds the maximum explosive force of the burning fuel, hence no movement. However, if the bolts weren't torqued down enough, even if they seemed 'tight', there would be movement over time and particularly right after a power stroke, to allow the bolts to work themselves free. Castled nuts I believe are more for applications where a slight amount of slop (even if it's only 1/1000 of an inch clearance) is allowed, or even preferred and particularly where there is rotational forces as in tapered bearings like on a trailer wheel or car wheel.
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