Torque Wrench Calibration
#2
02-10-2007 | 01:25 PM
Senior Member
Joined: Dec 2005
Posts: 774
From: Canada
RE: Torque Wrench Calibration
If you want some assurance without extreme accuracy, you can use a torque wrench of known accuracy to tighten a bolt to a mid-range torque, then put the wrench of unknow accuracy on there and see how tight it "says" the fastener is. If it's close, your laughing.
If it's not...........
What type of wrench do you have - dial, "click", or deflecting beam (long needle with scale near handle)?
If it's a delflecting beam, just make sure theneedle is pointing to zero at rest. These are simple,very reliable and, as long as you have a good view of the scale, accurate.
If it's a clicker, they're notoriously inaccurate, and you'll likely spend more for the calibration than the wrench is worth. Buy a replacemnet clickerand hope it's accurate off the shelf. Better still, replace it with the beam type.
If it's an expensive dial type, you'll still pay quite a bit for a calibration, but it'll be cheaper than buying another expensive oneof the same type.
Usually places that sell expensive torque wrenches can tell you the name of a local place where it can be calibrated. If you do indeed go for a calibration, tell them that you don't need a certificate of NIST traceability - you just want to know that it's accurate for you own peace of mind. Maybe they'll calibrate it for less money if they don't have to go the paper-trail route.
If it's not...........
What type of wrench do you have - dial, "click", or deflecting beam (long needle with scale near handle)?
If it's a delflecting beam, just make sure theneedle is pointing to zero at rest. These are simple,very reliable and, as long as you have a good view of the scale, accurate.
If it's a clicker, they're notoriously inaccurate, and you'll likely spend more for the calibration than the wrench is worth. Buy a replacemnet clickerand hope it's accurate off the shelf. Better still, replace it with the beam type.
If it's an expensive dial type, you'll still pay quite a bit for a calibration, but it'll be cheaper than buying another expensive oneof the same type.
Usually places that sell expensive torque wrenches can tell you the name of a local place where it can be calibrated. If you do indeed go for a calibration, tell them that you don't need a certificate of NIST traceability - you just want to know that it's accurate for you own peace of mind. Maybe they'll calibrate it for less money if they don't have to go the paper-trail route.
#3
02-10-2007 | 05:31 PM
Super Moderator
Joined: May 2006
Posts: 18,398
From: Wisconsin
RE: Torque Wrench Calibration
Clamp a socket or short extension in a vise, so the wrench sits vertically. Wrap a string or something around the handle, around some kind of pulley, & hang weights of the string. Measure the distance from the center of the socket to the place where the string is. Torque is weight x distance.
This assumes you know (REALLY know) the weight of your weights. A gallon of distilled water is8.34 pounds and the plastic bottle doesn't weigh much.
Dang, I was really stupid on that one. (I never work in gallons.) 62.4 pounds per cubic foot. Not per gallon. I fixed it...
[sm=imsorry.gif]
This assumes you know (REALLY know) the weight of your weights. A gallon of distilled water is8.34 pounds and the plastic bottle doesn't weigh much.
Dang, I was really stupid on that one. (I never work in gallons.) 62.4 pounds per cubic foot. Not per gallon. I fixed it...
[sm=imsorry.gif]
#5
02-10-2007 | 06:10 PM
Senior Member
Joined: Dec 2005
Posts: 774
From: Canada
RE: Torque Wrench Calibration
ORIGINAL: JimBlake
Clamp a socket or short extension in a vise, so the wrench sits vertically. Wrap a string or something around the handle, around some kind of pulley, & hang weights of the string. Measure the distance from the center of the socket to the place where the string is. Torque is weight x distance.
This assumes you know (REALLY know) the weight of your weights. A gallon of distilled water is 62.4 pounds and the plastic bottle doesn't weigh much.
Clamp a socket or short extension in a vise, so the wrench sits vertically. Wrap a string or something around the handle, around some kind of pulley, & hang weights of the string. Measure the distance from the center of the socket to the place where the string is. Torque is weight x distance.
This assumes you know (REALLY know) the weight of your weights. A gallon of distilled water is 62.4 pounds and the plastic bottle doesn't weigh much.
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