stanprophet Wrote:Just as I was re reading this thread, I wanted to further comment on this. While this is generally true, there are exceptions. I use torque wrenches daily in my line of work. Although I am not working on aircraft engines, or DOE reactors I have my torque wrenches checked ofter and calibrated when specs reach near maximum of rated percentile values. Any high quality wrench will actually give you a spec on percentage of accuracy over a given range. Some of the higher end models like snap on are very clear on that. Also many of the torque wrenches of high quality will far exceed the percentage of error between 20-80% of the range. I have a Snap On Split Beam type wrench that is used on a lot of non critical parts that have a range value. The split beam is rated from 50-250 ftlbs, at 4% +/-. I have found that the 70% of that range will average less than 1%. Even some of the best wrenches they make are +/- 1%. These are the wrenches that are the only ones approved by the D.O.E. for Reactor work. Even then the 1% is not a huge variance.

The use of a Torque wrench is really a compromise to begin with. The Idea is to be able to measure the fastener stretch, and in some cases that is the actual way I measure proper fastener torque. Of course this is impossible to do with some fasteners, so the compromise is to us a torque specification to try and engineer the proper stretch of a given fastener. In more recent years it has been found that since variances in fasteners, and friction under the fastener head and different designs of torquing tools, that torque values are not consistent. Many of the newer specs give a low value torque sequence, then continue the fastener stretch by using a specified degree.

For most application here this is really irrelevant to one extent, because engineering fastener stretch on the MSR is a little overkill. The name of the game for most things is consistency. Just like many people that reload and use a powder charger, it is more about being consistent. The way things are torqued needs to be consistent. So for things like barrel nuts, using a center range of the torque specs, with a crappy wrench will still yield a value well into the specified range. Even a wrench for scope rings, being off a good percentage, will still yield good results since all of the fasteners will be torqued consistent.

Just something I wanted to add that may help someone one day.