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+--- Thread: Torque Wrench Calibration (/showthread.php?tid=827)
Torque Wrench Calibration - Sijray21 - 08-16-2004
As the title says:
where can i get it done / what company can i ship it to and such?
I was an idiot and used it for multiple other things that it wasn't intended for. Still works fine (from what i can tell), i just don't know if its way off or anything.
- white_2kgt - 08-16-2004
Unless you are putting an engine or tranny together don't worry about it. Shouldn't be off by much unless you really abused it, then its probably better to just buy another one anywany.
-c
- BLINGMW - 08-16-2004
I thnk it's a really good question, I wonder who does calibrate these things? I've got a kind of cheap one, is there any way I can figure out how much it's off?
- Mike - 08-16-2004
BLINGMW Wrote:I thnk it's a really good question, I wonder who does calibrate these things? I've got a kind of cheap one, is there any way I can figure out how much it's off?
You'd need a good one to base it off of.
Torque to a certain # with the potentially bad one, set good one to that number and see if it tightens any.
then
Torque to a certain # with the good one, set the potentially bad one to that number and see if it tightens any.
- BLINGMW - 08-16-2004
SEEMS like a good idea to me, kind of like "calibrating" tire pressure gauges when you're at the track by borrowing others to compare, but I wonder if that method is really acurate at all. ISAT measurement and uncertianty would probably tell me no, if I remembered any of that. :wink:
- Mike - 08-16-2004
fuck isat. it's good enough for me.
- JohnC - 08-17-2004
You don't need to send it anywhere - use physics instead
Torque = Force * Distance
How long is the torque wrench? Let's call it distance d.
Get a brick, of weight w.
For "d = 1 ft" and "w = 1 lb", you could apply 1 ft-lb of torque.
Set the torque wrench to 1 ft-lb.
Attach the torque wrench to a securely fastened bolt somewhere.
Balance brick on torque wrench (or, use a scale to apply your known force to the end of the torque wrench).
You are now applying a known torque to your torque wrench. See if it clicks
Vary the forces around your target so make sure that it doesn't click for just under 1 ft-lb. Make sure it clicks for just over 1 ft-lb. I'm sure there are plenty of variations on this method that would probably be more interesting and accurate, but that's what I could come up with at 7:55am.ISAT folks chime in....
- Sijray21 - 08-17-2004
i thought about that, we'll see, the minimum marking on my torque wrench is 20 lbs*ft
- .RJ - 08-17-2004
Most torque wrenches arent accurate at the low/high end of their range
- BLINGMW - 08-17-2004
John's method sounds legit to me, it'd prob be best to have a pan hanging from a cable (steal one from local supermarket produce section) or something looped over the wrench so you could ensure the center of the weight was at x distance on the handle. You'd probably be able to test the higher end of the scale that way rather than trying to balance 100lbs on top of the handle or having a kid stand on it.
- JohnC - 08-17-2004
BLINGMW Wrote:John's method sounds legit to me, it'd prob be best to have a pan hanging from a cable (steal one from local supermarket produce section) or something looped over the wrench so you could ensure the center of the weight was at x distance on the handle. You'd probably be able to test the higher end of the scale that way rather than trying to balance 100lbs on top of the handle or having a kid stand on it.
I was thinking some more about it... Would you have to take into account the weight of the torque wrench itself, to insure an accurate measurement? Some googling revealed the the "Federal Standard" is something like "accurate within 4%". So, for setting of 100ft-lbs, anything between 96 - 104 is fine? Surely a heavy duty torque wrench could weight > 4 lbs (although wouldn't accuracy demand an integral to take into account the delta-d along the length of the wrench? - oh boy, calculus!).
However, if you applied a horizontal force to a torque wrench suspended vertically, then the wrench's downward force wouldn't generate any torque (in an axis that matters) against the bolt. So, maybe use a pulley in combination with the hanging pan. Egad, I'm thinking about this way (weigh) too much :roll:
- .RJ - 08-17-2004
If I were building an engine, I dont think +/- 4% is acceptable...
Although you dont use a torque wrench on all of the critical fasteners anyways....
- Evan - 08-17-2004
.RJ Wrote:Most torque wrenches arent accurate at the low/high end of their range
I have heard that it is just the opposite, they are the most accurate in the top 10% of their torque range.
- Mike - 08-18-2004
MichaelJComputer Wrote:fuck isat.
ut-oh...
so i'm testing the screen name suggester here... i input three fields: first name, last name, and the screenname i want. i put first name as "this", last name as "isa", and screenname as "test." it came back with five results, one being "isat."
how fucked up is that? i'm doomed for talking bad about isat.