Home Forums Hunting & Shooting Hunting Optics Which torque wrench is better: Wheeler Fat Handle or Weaver?

Wheeler FAT and Weaver adjustable torque screwdrivers accuracy rely on linear characteristics of the spring, which loads torque limiting clutch. They have identical principal design, with Weaver having a bit longer spring, which, both theoretically and practically, is a better way to ensure tool accuracy in mass production (1) and to make adjustment scale a bit longer for better readability by the user (2).

Initial adjustment (or calibration) is done at the factory for only ONE specific torque setting, typically the one in the middle of torque adjustment range. Accuracy within the whole adjustment range then depends upon linear characteristics of the spring, and nothing can be done about it. Typically, spring rate is found to be linear and may be reliably "synchronized" with adjustment scale if active spring load is between 20% and 80% of the maximum spring load. Which means that adjustable torque screwdriver may have decent accuracy if it is used for outputting the torque with adjustment ratio of 1 to 4 (from 20% to 80%) or so.

Wheeler FAT has an adjustment ratio of 10 to 60 inch-lbs. (1 to 6 ratio), Weaver has theoretically less favorable adjustment ratio of 10 inch-lbs. to 80 inch-lbs. ( 1 to 8 ratio), but has longer scale and slightly better scale resolution than FAT.

In my opinion, Weaver branded adjustable torque screwdriver supplied by Da-Jiun Co. from Taiwan is overall better made than Wheeler branded tool made in China (not sure which company in China makes this one).

Harbor Freight (from China) wrench with 20 to 200 inch-lbs. torque adjustment provides ratio of 1:10, which is really "pushing it" above proven technology,so do not expect any miracles of accuracy at low and high torque settings with that HF product.

Initial factory calibration to a single torque setting in the middle of the adjustment range, which is likely matches 45-50% of the spring load, is done with use of shim washers, which are typically custom made and installed during tool assembly at the factory.

Repeatability, in general, is ensured by the quality of parts used for assembly. If parts of the torque limiting clutch and spring itself are of high quality, means these parts are made from good materials/properly heat treated, then tool parts wear will be minimized to acceptable levels and repeatability will be preserved over considerable period of time. Repeatability also depends how well the tools user can see the scale markings and the scale pointer, which is, naturally, a subjective factor.

To summarize - adjustable torque screwdrivers like Wheeler FAT and Weaver can be re-calibrated, but only for ONE specific torque setting within the whole adjustment range. However, such re-calibration requires the use of the custom parts (shim washers), which are not likely to be easily obtainable by the individual owner of the tool or even by the test lab. This is because these shim washers, being of proprietary design, are not likely to be available from industrial supply companies like McMaster Carr and others.

These adjustable screwdrivers can be, of course, also checked (verified) for various torque settings within the range. If results of verification shows that torque output matches adjustment scale, say, in the middle of the range and does not match the scale at both ends of the same scale within claimed deviation, say, of no more than +/-6%, nothing can be done about it.

If parts used for torque limiting mechanism lack quality, repeatability will go to hell after some relatively short use, and nothing can be done about it.

And testing, say, of 10 adjustable screwdrivers, either Wheeler FAT or Wheeler, is not going to determine that, say, the other 100,000 of them are good or not, these tools are massed produced in Asia, where quality is typically hit or miss depending upon specific batch of tools. BTW, this happens not just with Asia made products, I've seen it done by some U.S. suppliers as well, but, statistically, on a lesser scale.

Yes, you can send your particular tool to test lab, but results of such test may not give sufficient info to determine which of the two tool brands is "better". In addition, results of such test may not help at all to fix potential issues with accuracy and repeatability, if any are found.

In my opinion, if testing is done without having an option to fix potential issues, it's useless waste of time. To make everything more practical and less stressful, just buy quality tools.