ZR-1 Net Registry Forums - View Single Post - Neat link for torque (tools) calculators>>>

8upZR1 · 01-14-2009

Its early in the morning so I will add this ultra depressing, unfortunately true story to the mix. I worked in an IC engines lab a few years ago and in the back they kept all the ancient engine/component testing euipment. One day I was back there and noticed attached to the wall a torque wrench tester. It was old but really nice. It basically had a weight on an arm connected by a shaft on ball bearings supports to a 1/4" drive female end. A large needle pointer was attached and read off of a gauge, so that when the weighted arm was @ 90 to vertical it showed full torque (arm length X force from weight). The needle would hold the highest recorded torque until reset. I ended up cleaning the thing and putting new bearings in and then proceeded to test my torque wrenches. These were German made professional torque wrenches I had inherited from my father. They had the slider deal to adjust torque. All 3 were between 15-20 ft-lbs off the mark. After my coworkers caw what I was doing they got curious and the next day everyone brought their torque wrenches. We had about 15 wrenches and everyone claimed theirs was spot on, and all but 1 failed. The wrench that was spot on was a $1000 professional deal that had been calibrated just the month before. The others ranged from cheap to expensive so we had a good mix. It was incredibly scary to see. One of the biggest issues with some wrenches was the amount of play in the adjuster and the gauge. After that little contest I decided to use the torque tester to set the wrench before each use and not even look at what the wrench says.

I think being consistent about how you read, set, and pull the wrench is also critical for repeatabilty. Im not saying everyone needs an expensive torque wrench, just that you need to calibrate yours to you somehow.

Even if the wrench is performing with 100% accuracy there is always the issue of inconsistencies with the fastener and threads and if your torque is being converted into clamping load. I know whenever I tighten rod bolts that I do my absolute to ensure clean threads, and I use plenty of moly. I set my torque wrench to spec, and yet the amount of stretch differs from one bolt to the next. In a set of 8 rods I usually have 5 fasteners that stetch to spec when the torque spec is applied and the rest stretch somewhere around .0010 under.

Dont put to much trust into a torque wrench that you dont know is at least relatively accurate.

01-14-2009	#6
8upZR1 Join Date: Jun 2006 Location: Thunderbolt, Ga. Posts: 253	Re: Neat link for torque (tools) calculators>>> Its early in the morning so I will add this ultra depressing, unfortunately true story to the mix. I worked in an IC engines lab a few years ago and in the back they kept all the ancient engine/component testing euipment. One day I was back there and noticed attached to the wall a torque wrench tester. It was old but really nice. It basically had a weight on an arm connected by a shaft on ball bearings supports to a 1/4" drive female end. A large needle pointer was attached and read off of a gauge, so that when the weighted arm was @ 90 to vertical it showed full torque (arm length X force from weight). The needle would hold the highest recorded torque until reset. I ended up cleaning the thing and putting new bearings in and then proceeded to test my torque wrenches. These were German made professional torque wrenches I had inherited from my father. They had the slider deal to adjust torque. All 3 were between 15-20 ft-lbs off the mark. After my coworkers caw what I was doing they got curious and the next day everyone brought their torque wrenches. We had about 15 wrenches and everyone claimed theirs was spot on, and all but 1 failed. The wrench that was spot on was a $1000 professional deal that had been calibrated just the month before. The others ranged from cheap to expensive so we had a good mix. It was incredibly scary to see. One of the biggest issues with some wrenches was the amount of play in the adjuster and the gauge. After that little contest I decided to use the torque tester to set the wrench before each use and not even look at what the wrench says. I think being consistent about how you read, set, and pull the wrench is also critical for repeatabilty. Im not saying everyone needs an expensive torque wrench, just that you need to calibrate yours to you somehow. Even if the wrench is performing with 100% accuracy there is always the issue of inconsistencies with the fastener and threads and if your torque is being converted into clamping load. I know whenever I tighten rod bolts that I do my absolute to ensure clean threads, and I use plenty of moly. I set my torque wrench to spec, and yet the amount of stretch differs from one bolt to the next. In a set of 8 rods I usually have 5 fasteners that stetch to spec when the torque spec is applied and the rest stretch somewhere around .0010 under. Dont put to much trust into a torque wrench that you dont know is at least relatively accurate.