Torque wrench calibration
Discussion
I doubt how useful torque wrench calibration is. Can they guarantee accuracy over the full range of your torque wrench settings? I'm not sure that's even possible to achieve on the standard mechanic's torque wrench.
I worked on aircraft for twenty years. We would always set up our torque wrenches on an Acratork Rig for each torque setting to be used, before taking them to the aircraft. They were a feature of every maintenance hangar or flight line tool stores.
http://www.mechmetrology.co.uk/product94.html
The RAF used to calibrate torque wrenches and Acratork rigs every six months. You weren't allowed to use it without an in-date calibration sticker. Yet we would often still see quite a discrepancy between the torque wrench setting and reading on the Acratork dial.
I think the answer is to buy the best quality torque wrench you can afford and take good care of it.
I worked on aircraft for twenty years. We would always set up our torque wrenches on an Acratork Rig for each torque setting to be used, before taking them to the aircraft. They were a feature of every maintenance hangar or flight line tool stores.
http://www.mechmetrology.co.uk/product94.html
The RAF used to calibrate torque wrenches and Acratork rigs every six months. You weren't allowed to use it without an in-date calibration sticker. Yet we would often still see quite a discrepancy between the torque wrench setting and reading on the Acratork dial.
I think the answer is to buy the best quality torque wrench you can afford and take good care of it.
Edited by JoeBolt on Friday 23 December 15:42
Even cheaper to calibrate it yourself!
Torque as "pound-feet" means what it says. The force is that of X pounds exerted through a lever Y feet long. The two values are multiplied together.
So set up your wrench in a vice by the drive bar, so that the lever moves in a vertical plane.
Take a heavy weight, of the order that A/ you can manage and B/ is within your wrench's range.
I use a 20kg flywheel (44lbs).
My wrench is a bit over two feet long, so I set it to 80lbs-ft, and hang the wheel by a strap from the handle.
Move the strap outwards, until it just clicks.
Measure the distance of the weight from the drive bar, in feet or meters - metric torque is in N-m, aka Newton-metres, where a Newton is the force under gravity of the weight.
Do the maths - multiply feet by pounds or go metric.
If my wrench is accurate, the 44lb weight will click it just 22ins (1.8 feet) from the drive bar. (44 x 1.8 = 79.2 - I rounded!)
John
Torque as "pound-feet" means what it says. The force is that of X pounds exerted through a lever Y feet long. The two values are multiplied together.
So set up your wrench in a vice by the drive bar, so that the lever moves in a vertical plane.
Take a heavy weight, of the order that A/ you can manage and B/ is within your wrench's range.
I use a 20kg flywheel (44lbs).
My wrench is a bit over two feet long, so I set it to 80lbs-ft, and hang the wheel by a strap from the handle.
Move the strap outwards, until it just clicks.
Measure the distance of the weight from the drive bar, in feet or meters - metric torque is in N-m, aka Newton-metres, where a Newton is the force under gravity of the weight.
Do the maths - multiply feet by pounds or go metric.
If my wrench is accurate, the 44lb weight will click it just 22ins (1.8 feet) from the drive bar. (44 x 1.8 = 79.2 - I rounded!)
John
Edited by tapkaJohnD on Sunday 25th December 10:45
tapkaJohnD said:
Even cheaper to calibrate it yourself!
Torque as "pound-feet" means what it says. The force is that of X pounds exerted through a lever Y feet long. The two values are multiplied together.
So set up your wrench in a vice by the drive bar, so that the lever moves in a vertical plane.
Take a heavy weight, of the order that A/ you can manage and B/ is within your wrench's range.
I use a 20kg flywheel (44lbs).
My wrench is a bit over two feet long, so I set it to 80lbs-ft, and hang the wheel by a strap from the handle.
Move the strap outwards, until it just clicks.
Measure the distance of the weight from the drive bar, in feet or meters - metric torque is in N-m, aka Newton-metres, where a Newton is the force under gravity of the weight.
Do the maths - multiply feet by pounds or go metric.
If my wrench is accurate, the 44lb weight will click it just 22ins (1.8 feet) from the drive bar. (44 x 1.8 = 79.2 - I rounded!)
John
You've described how to test a torque wrench, not calibrate one.Torque as "pound-feet" means what it says. The force is that of X pounds exerted through a lever Y feet long. The two values are multiplied together.
So set up your wrench in a vice by the drive bar, so that the lever moves in a vertical plane.
Take a heavy weight, of the order that A/ you can manage and B/ is within your wrench's range.
I use a 20kg flywheel (44lbs).
My wrench is a bit over two feet long, so I set it to 80lbs-ft, and hang the wheel by a strap from the handle.
Move the strap outwards, until it just clicks.
Measure the distance of the weight from the drive bar, in feet or meters - metric torque is in N-m, aka Newton-metres, where a Newton is the force under gravity of the weight.
Do the maths - multiply feet by pounds or go metric.
If my wrench is accurate, the 44lb weight will click it just 22ins (1.8 feet) from the drive bar. (44 x 1.8 = 79.2 - I rounded!)
John
Edited by tapkaJohnD on Sunday 25th December 10:45
voicey said:
tapkaJohnD said:
Even cheaper to calibrate it yourself!
Torque as "pound-feet" means what it says. The force is that of X pounds exerted through a lever Y feet long. The two values are multiplied together.
So set up your wrench in a vice by the drive bar, so that the lever moves in a vertical plane.
Take a heavy weight, of the order that A/ you can manage and B/ is within your wrench's range.
I use a 20kg flywheel (44lbs).
My wrench is a bit over two feet long, so I set it to 80lbs-ft, and hang the wheel by a strap from the handle.
Move the strap outwards, until it just clicks.
Measure the distance of the weight from the drive bar, in feet or meters - metric torque is in N-m, aka Newton-metres, where a Newton is the force under gravity of the weight.
Do the maths - multiply feet by pounds or go metric.
If my wrench is accurate, the 44lb weight will click it just 22ins (1.8 feet) from the drive bar. (44 x 1.8 = 79.2 - I rounded!)
John
Yes he has, and if it tests as satisfactory then no calibration is necessary. This will cover 99pc of cases.Torque as "pound-feet" means what it says. The force is that of X pounds exerted through a lever Y feet long. The two values are multiplied together.
So set up your wrench in a vice by the drive bar, so that the lever moves in a vertical plane.
Take a heavy weight, of the order that A/ you can manage and B/ is within your wrench's range.
I use a 20kg flywheel (44lbs).
My wrench is a bit over two feet long, so I set it to 80lbs-ft, and hang the wheel by a strap from the handle.
Move the strap outwards, until it just clicks.
Measure the distance of the weight from the drive bar, in feet or meters - metric torque is in N-m, aka Newton-metres, where a Newton is the force under gravity of the weight.
Do the maths - multiply feet by pounds or go metric.
If my wrench is accurate, the 44lb weight will click it just 22ins (1.8 feet) from the drive bar. (44 x 1.8 = 79.2 - I rounded!)
John
Edited by tapkaJohnD on Sunday 25th December 10:45
You've described how to test a torque wrench, not calibrate one.
GarageQueen said:
anyone had torque wrenches calibrated in the uk, any recommendations?
We send our work ones back to Gedore every 12 months. Head office is in Skipton but i'm sure they have a few places around the country. Some bigger customers like to see the calibration certificates on certain jobs.
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