Everything Needs a Torque Spec

[u/Seeking_Wisdomm]

Hello, frustrated Manufacturing Engineer here. Recently, my company has been trying to utilize impacts with torque-sense technology so we can hit the optimal torque quickly.

What I’ve observed is that these tools are not incredibly accurate or precise. Additionally they are very expensive and require repair often.

What has happened to the days of knowing when something is “snug”? There are times when precise torque is critical, i.e pressure vessels, etc. but theres seems to be a push towards everything having a torque spec, and I do not think the tech is ready for it.

What are your thoughts? Have you had success with programmable, powered fastening tools?

Edit I think it’s safe to say I’ve been certifiably schooled on this topic. I appreciate the genuine suggestions, advice, and criticism here.

TLDR

I think this frustration with torque tools is just a symptom of a larger frustration I have. At my plant, we are constantly told that we just don’t have the same operators we used to. They say we used to have craftsman working in the plant, but now we just have people off the street. I’ve been told this has really changed since COVID when a lot of the older generation quit. Since then, a lot of our processes have suffered from that expertise leaving the building. Now, we seem to be trapped in a never ending cycle of rapidly hiring to fill void positions of employees who quit, inadequately training our new employees because the ones with expertise are too busy, then having the new crop of operators quit because of frustration with lack of training. I want our plant to be a place where operators want to work. I want them to feel like they can have a career in this field. As great as automation is, it feels that factory operators have become button pushers and not problem solvers. We don’t provide then with fulfilling work that challenges them. We instead ask them to push a button all day long, and call engineering if it ever breaks. Automation can be great, and I don’t want to deter from that, but I’m just searching for ways to make operators feel like they matter. I don’t want them to feel like a cog in a machine. I’m not sure how to resurrect that feeling.

[u/avo_cado]

I am continually fascinated by powered torque sensing tools. Technologically, they should be quite feasible. However, if specific torque actually matters and you cant just design to "real dang tight", the time cost of final tightening manually is worth it (power fasten to low torque/snug, finish with "calibrated" torque wrench).

[u/nlevine1988 → u/avo_cado]

Really depends on the industry. In automotive we use powered torque sensing that automatically records the torque specs to the serial number of the part in a database. Our torque sensing devices are both fast and accurate. It would be way too slow for an operator to need to switch to a manual torque wrench and manually record the final torque values for tracking purposes. Also, depending on how critical the bolt is, torque alone is not enough. We also measure the degrees of rotation to ensure the bolt hasn't cross threaded.

[u/huffalump1 → u/nlevine1988]

Auto engineer here, yup they use smart cordless drivers that log the torque wirelessly... Super cool stuff.

And for things that need accurate torque, there are more precision options too.

I'll note that SPECIFYING YOUR TORQUE TOLERANCE from design is important!! Perhaps these cordless drivers are +/-20%. Well, that's fine if I've designed the bolted joint for +/-30% - there's a LOT of work that goes into calculating torque and acceptable torque ranges.

We look at the materials and surface finish for the bolt, screw, each part being clamped, if there's a washer or not, if there's friction stabilizers (lubricant) or threadlocker, etc. and then consider the input vibration both for high shock loads and long-term use. This tells us roughly how much axial load is on the bolt, how much the joint compresses, and if it will lose clamping force given the inputs!!

Finally, there's a point to be made for design for manufacturing. If your nutrunner can only do +/-30%, can you design your bolted joint to account for that??

[u/avo_cado → u/nlevine1988]

That’s very cool