What torque settings for accessory screws.

As a newish teacher I am trying to get students to fix things with the correct amount of torque.

Tightening brass screws like they are wheel nuts does not give materials much of a lifespan.

So I bought a couple of torque screwdrivers, so they can quickly get a feel for how tight things should be.

However now I look at data sheets I can't seem to find Torque info for anything smaller than a a miniature circuit breaker.

The data sheets now often include other everyday information like Altitude.

Does anyone have some guidance for smaller brass screw torques, or know of a manufacturer that publishes such data?

  • And realising that only the reversible (elastic) distortion that actually holds connections tight - the strand spreading  and  any distortion/damage that does not return to its original shape on loosening may increase the contact area but does not contribute to the contact pressure. It may however use up a lot of the torque - so tightening 'identical' wires into 'identical' fixings  has a lot in common with measuring a selection of walnuts with a micrometer, a different very accurate answer each time.

    However as a lesson for students, and important one, as loose terminals are very much a hazard - there is a lot to be said for designs with definite spring pre-load, by using star washers under things that matter.and constant force springs on pipes etc. The stcrew looks simple but it hides a lot of complexity that is often overlooked.

    I;d suggest also that they try torque tests with lids on adaptable boxes, and with and without some sort of spring / star washer under the head.

    Then flash up a slide of these jackbolts.


    The idea is that for really large bolts the rotating of the nut and the ultimate  tensioning up of the bolt can be made independent actions. Seen on things like wind turbines and large ships.

    For making people think about environments with a lot of shake rattle and roll for everything else. this video of various fasteners on a shaker table is worth watching, if a bit of an advert. Note they do not test star washers, if they had then it would show they can be  pretty good.

    The fun starts about 1 minute in,  after the introductory flannel


  • The large bolt tightening hydraulic "pullers" for the bolt (stud) are interesting, there are a couple of ship engine videos on youtube. The tension in a 50mm grade 16 stud might well be 150 tons, and getting that force with a screw thread is an impossible torque, even with a very fine thread! "Given a long enough lever I can move the Earth comes to mind".

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