Do techs use torque wrenches to do repairs?

[Doubler]

Unless you calibrate the torque wrench at it's required interval or after you drop it you are wasting your time using it. For a bar type wrench if you torque something clockwise to 15 in. lbs. you must also do a torque to 15. in lbs counter clockwise, this keeps the bar tension balanced. Checking an applied torque when you get home is basically a waste of time. The torque will relax based on material, grease, oil, stretch, friction, oring squeeze etc. At work we waste our time yearly during an annual inspection checking breakaway torques. After ten years of doing these inspections this was the first year we had one weapon whose values were all within breakaway spec, usually 1/3 fail. The one with zero errors had originally been built using a German self calibrating electronic torque wrench, others using the same torque wrench failed at the same rate as mechanical torque wrenches. Weird. The only true way to accomplish a valid test requires thousands of dollars of equipment. Engineers spend hours and companies lots of money to determine proper torques for a reason, techs should use them.

 

[Mr Carcharodon]

None of the three shops in my area use torque wrenches. Two of the three broadly disregard the manufacturer’s service manuals. The third technician maintains a veil of secrecy about the procedures he performs which inspires no confidence at all. Since swivel nut over torquing has lead to catastrophic failures of first stages due the swivel separating from the regulator body it would be hard to say there is not a potential safety issue.

But what is the technicians incentive to do it right? After all in most cases when they break parts due to their failure to follow instructions they will not pay for the broken parts. Their customers will or they will make a warranty claim. And since most of the work is done outside of the light of day there is little pressure against incompetent or shoddy work.

Really everyone should read their manufacturer’s service manual. Most of them are available on the web. Ask your tech about his planned service, and see for yourself how well it matches what the manufacturer recommends. You will be shocked.

 

[Dmdusn]

I watched a boat mechanic install spark plugs in my engine and asked him why he was not using a torque wrench (steel plugs in an aluminum head with a spec of 17 ft-lb). He said he had done it so much he didn't need one. I checked the torque on all the plugs when I got home. Torque ranged from about 10 ft-lb to almost 25 ft-lb. He lost a customer.

Dive shops that do not have a torque wrench definitely do not use them. Ask your shop to see their torque wrenches.

Not sure if I'm the minority here, but I've never once used a torque wrench on a spark plug. Overkill if you ask me. Two fingers on the end of the ratchet, snug it up, done.

 

[halocline]

These days my car uses a lot of torque-to-yield single use bolts; I suspect lots of cars do. The head bolts on my car, and the engine mount bolts, are TTY. You go whatever the spec is and 90o over or something similar. You think any decent mechanic doesn't use a torque wrench in situations like that?

 

[Peter_C]

Not sure if I'm the minority here, but I've never once used a torque wrench on a spark plug. Overkill if you ask me. Two fingers on the end of the ratchet, snug it up, done.

I recently made my employee, who is new to the automotive field, although a born natural, look up and torque a set of spark plugs so he could "feel" what it should be like. He has also torqued different bolts at times on his own just to learn what "X" foot pounds fells like.

 

[Dmdusn]

These days my car uses a lot of torque-to-yield single use bolts; I suspect lots of cars do. The head bolts on my car, and the engine mount bolts, are TTY. You go whatever the spec is and 90o over or something similar. You think any decent mechanic doesn't use a torque wrench in situations like that?

No, I think mechanics guess at everything. Thanks for the snark.

 

[tyesai]

Torque wrenches are overrated. Any decent mechanic knows that when a small nut specifies a light torque of 20 inch pounds that barely tight is good enough, and when a large nut needs 1000 inch pounds you need a big wrench and all your back, maybe your buddies back too.

That said I use them at work on the aircraft, but there was also a time when aircraft mechanics, at least in the old C-130 world rarely used them. But I always did and do at work and thats my official answer.

I've never even considered using a torque wrench on a car or motorcycle, at least not for changing plugs, tires, oil, ect; Maybe if I was putting together a motor, but even then I've helped rebuild Harleys ( I hate them, but free beer is free beer ) I don't remember using a torque wrench. ( we might have, it was free beer, I drank a lot back then )

I don't know much about regs, and have to help tear one apart and put it back together to see how I felt about not using a torque wrench, but I'd probably refer to my first statement.

 

[tbone1004]

I was the poster in question. My service manual states until metal touches metal. It's to prevent stripping of threads, and warping of stuff.
O-rings are there for a reason. As stated by a bunch of other people in here, it's usually to prevent OVER tightening. When you're tightening something metal to metal, it's real easy to over-tighten it, but it's pretty difficult to under-tighten it. If it's under at all, it'll spin freely. Snug works, snug is NOT wrenched down. With normal allen keys, I use the shorter end to tighten. If you can put more torque on the short end of an allen key with your bare hands, well the more power to you. You do it enough, and you can feel when it's right.
Yoke is a lot different than DIN, and usually require some funky wrenches to get that nut tight. That's the one nut we actually put a torque wrench on just because of the way it works. It needs to spin freely but still be stable, so we do use it there. On port plugs, hoses, DIN adapters etc, there's no need. That being said. One of the shops here is a VERY highly regarded repair shop. I know they use torque wrenches, a. because I've seen them, and b. when they work on my Poseidons I can't get the port plugs or hoses off with normal allen keys and small wrenches. So I guess mine are under the recommended torque, but I've never had anything blow out because of it, and when I'm diving, if all of a sudden I have a hose blow, or need to add an extra inflater, I don't want to have to fight my first stages or need to bring a vice and torque wrench to get a port plug out *Yes I did have to vice the first stage and get a long allen key to get these port plugs out*.
Once you tighten everything to manufacturer specs you realize how tight it actually is. You also notice that one of the things going around the cave community was finger tightening second stages. They are under the same IP as the port plugs and hoses on the first stages. As well as the turret bolts if they have them. If finger tight will hold a regulator on it's hose, then a smidge tighter with an allen key will hold a port plug in

 

[Max Speed]

Consider that Armalite had MORE loose carrier keys on new rifles AFTER they began requiring their techs to use torque wrenches on the two allen screws.

It seems that human "feel" for the correct torque can produce better results than a design engineer's reference book. Especially when that engineer may have never seen or used the finished product. Trust your "feel" and common sense first. Use a torque wrench as a crutch or backup to your own good judgement. The accuracy of a torque wrench in actually setting bolt stretch is not nearly what you expect! Hence, use of angle torqueing or bolt stretch measurements for critical applications.....

 

[LeadTurn_SD]

I was the poster in question. My service manual states until metal touches metal. It's to prevent stripping of threads, and warping of stuff.....

For servicing Apex, Zeagle, Mares and maybe other diaphragm first stages, when tightening the diaphgram clamp ring, "metal to metal" probably does trump torque specs, and is what I do... But this is because of the possibility of false-high torque readings from friction of the diaphragm against the mating surface of the clamp ring.... But if you can't achieve metal to metal when tightening with a "reasonable" amount of torque, you need to step back and recheck that the diaphragm is correctly seated, etc.

There are applications where "metal to metal", or "snug" by feel instead of torqued to "spec" is just not good practice. Turret retaining bolts and yolk bolts spring to mind. Especially with turret bolts, there have been catastrophic failures (entire turret separating underwater) as a result of failure of the bolt. The failures were most often caused by repeated overtightening (not using a torque wrench).

So, for many applications, I'm just fine for tightening by "feel"... but for critical parts: torque wrench. Both for scuba, and certain engine / transmission repairs.

Best wishes.