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Torque limited screwdrivers

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tszaboo:
I have a set of Wera 7400 series torque limited screw drivers at work. It's a set of 3 hex drivers which can be set up between 0.3 and 6 Nm. Wera 05074739001
I have now a bit of obsession with this, as it is very nice/satisfying to be able to assemble something without the fear of ripping screws. And it's good for R&D when you need to be able to tell production what torques to use when assembling something. For example I run into several occasions, when an enclosure assembled with a certain torque was fulfilling it's IP rating, but not below, or above that. And I want to be able to do this at home as well. The set is about 250 EUR, which is a bit too much for my liking.

So this is a topic about torque limited screwdrivers.
Share your experience!

TERRA Operative:
I have a CDI brand 401NSM-CDI torque screwdriver that I don't use as much as I should...
It's great when I do use it. Most often for torquing components down to heat sinks to make sure they are tight enough without stressing the component.

I also picked up a Tone brand TBS20 'Torque Bit Ratchet Set' recently that I haven't used yet, but it looks pretty good.

jpanhalt:
I hate non-answers to questions posted on blogs, but maybe my experience is slightly relevant.  I like the idea of a torque measuring screwdriver and have often considered buying one.  For home use, there are a lot less expensive torque-indicating drivers available, and modern digital versions are very attractive.  I just haven't pulled the trigger yet.  I do have experience with torque wrenches and currently have 5  dating over generations to the 1960's.  My oldest are Craftsman, made in USA, and torque bar indicating.

Torque limited v. torque indicating:  I worked with a considerably older and experienced AI mechanic in the 70's and 80's on civilian aircraft. He would not allow a click-type torque limiting wrench on critical components, which included spark plugs.  However, there is no argument that clicker wrenches are easier to use particularly when working in limited space and difficult visibility.  That is what I usually use today on my car and implements.  I always use torque indicating on spark plugs and other things screwed into aluminum heads.

With respect to my hobby electronics and home, the biggest problem is with coarse threaded, "thread forming" screws in soft materials like plastic, aluminum, and sheet metal.  The risk of cross threading and destroying existing threads is high.  Do that a few times, and there are no more threads.  The best solution is to turn the fastener backwards until you just feel a little click or give, then proceed to turn in the correct direction, which is usually clockwise.  That first turn is critical, and if there is more than the usual low resistance, repeat the procedure to find the correct thread start.  A dedicated screwdriver (i.e., one without removable bits) is best for feel, but not required.  Final torque is up to you.  For home use, snug or just a little beyond it is all I do.  In sheet metal, too loose a fastener can allow the screw to get slightly cross-threaded and needs to be avoided.   

tszaboo:

--- Quote from: jpanhalt on April 07, 2024, 12:03:52 pm ---Torque limited v. torque indicating:  I worked with a considerably older and experienced AI mechanic in the 70's and 80's on civilian aircraft. He would not allow a click-type torque limiting wrench on critical components, which included spark plugs.  However, there is no argument that clicker wrenches are easier to use particularly when working in limited space and difficult visibility.  That is what I usually use today on my car and implements.  I always use torque indicating on spark plugs and other things screwed into aluminum heads.

--- End quote ---
For wrench, maybe. For a 1/4in hex screwdriver, I don't see how the limit vs indicator would make a difference. We are dealing with 1/10th the torque on these screws, instead of bolts. It's very different. The Wera doesn't actually click, it skips and turns 1/6th maybe 1/4th when the preset torque is reached.

jpanhalt:
In terms of accuracy for small fasteners in non-critical applications, there is probably not much difference between and indicator and limit torque tool.

However, I prefer a gauge to idiot lights almost without exception when I can see the gauge.  In all instances, I still go by feel regardless of whether it is a spark plug or mounting screw for a PCB.  The indicator/gauge is confirmation and backup.  For non-critical items, when it feels right, I usually stop even if the desired torque has not been reached. 

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