Do techs use torque wrenches to do repairs?

[tbone1004]

Again, it's by repeated OVER tightening though. When we took the class our instructor had us to it with the torque wrench to get the feel, then had us put it on where we thought felt right. We were always about 5-10lbs short with the exception of one guy who felt the need to muscle it. 5-10lbs short is not going to cause anything from overtightening, and they were still on there pretty good and weren't coming off any time soon. They have their place for sure, but if the torque wrenches are to keep you from over tightening it's a lot safer to be a few pounds short, than on something like a I'm stupid where they are often to make sure they are on tight enough. We do most of our own mechanical stuff on our cars and to get some of those bolts up to spec, you have to crank on em pretty hard... Some like plugs not so much, but a few of those bolts are on there pretty good

 

[HenrikBP]

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.....

... and what exactly do you think is accomplished by torquing a bolt to specs if not appropriate bolt stretch/clamping force ...

Henrik

 

[Tortuga68]

Like Max said in your quote, the reading on a torque wrench and the clamping force of a fastener are not the same thing. For the same torque reading the clamping force can vary wildy, for example due to contamination or lubrication of the threads

 

[SCUBASailor]

I'm really glad I posted this thread. It's been very informative. The surprising thing to me is the general consensus that the real danger is from over tightening rather than under tightening. To saxplayer, I'm glad you posted, it gave me more insight into your original post. I work in an electrical environment, so to not be certain that we stay within specs can be a huge mistake. In my line of work, it pays to be OCD. That's why I was surprised regarding torqueing.

 

[D_B]

haven't read the hole thread but I have a comment about the torque wrench ... Our factory spec engine repairs use torque angle for head bolts and such, and not torque specs
oops, I see that Tourtuga has it covered :blush:

 

[captain]

I have built racing engines and the surest way to correctly tighten a connecting rod bolt is by measuring stretch. Rod bolts are stretched .007. The recommend torque on a clean lubricated 3/8" rod bolt is 45 ft/#. It takes a whole lot more torque than that to get to .007" stretch. So much so that I had to make a special wrench to be able to read the stretch gauge and tighten the bolt at the same time, a normal length wrench wouldn't cut it.

That said about the only thing I use a torque wrench on are main bearing caps, head and manifold bolts and wheel lugs.

I use a dab of locking compound and snug on the turret bolt on my MK V.

 

[tbone1004]

I'm a mechanical engineering... bout as dangerous as you electrical guru's if we do something wrong. Oh, uh sorry boss but that bridge girder's factor of safety was only .2 so that dump truck just fell through. woops.

The dedicated repair shops, Airtech in Raleigh for example, have to use torque wrenches just because that's what they do. They only service gear, and they are wicked good at it. I have seen some of their techs dive before and on their own gear they don't use the wrenches. Just not needed, but on their own gear it's no liability. They charge a lot of money to do service work for the average diver and the average diver isn't moving port plugs and hoses around, so they torque to spec. Trust me, they are a BEAR to get off, same when the yoke and DIN plugs are torqued to spec. If the yoke or din screws are too loose they'll blow when you pressurize the system usually. Not a big deal and I had it happen to me once when I was using a Yoke adapter. Somehow the bolt got caught and it got spun around a few too many times to loosen. Heard gas escaping. Took adapter off, screwed it back in finger tight, put it on and it was good for the next 5 dives of the day *was doing OW training babysitting duty*. The actual yoke bolts are a bit more dangerous since they will tend to shoot the 1st stage at the back of your head, hence why I'll actually use them for that, but we don't take those off very often, and it's never in the field.

 

[bracko]

Some torque specs are more critical than others. The old scubapro MK5 had a brass turret bolt that was easily damaged by over tightening; later MK20s had a yoke bolt that could damage the body if they were over tightened. In both cases SP changed the part to make the reg more "idiot proof" for servicing. It's pretty scary when the scuba gear companies insist that consumers leave the servicing to the certified "experts" and then consistently modify the regs because they lack faith in the ability of those "experts."

Other torque specs, like for port plugs, are not crucial and nobody I've ever seen uses a torque wrench to install those.

i don't think it is at all. it's a design process to innovate, then simplify.

even if you have a good qualified tech putting together your gear, it's inevitable he will damage something, some time. when the ramifications of that are possible death to a user, the companies designing the gear are going to take notice.

so the designers are going to have to make a decision. design a testing rig to test for these possible failures, or innovate and simplify.

testing rigs are expensive and obsolescence is a problem...

 

[Lake Muroc Diver]

It has been mentioned in this string, some techs can not be trusted to even use the correct tool. My poor computer had a visit to the dive shop for a problem and the eventual outcome was, they only changed the battery. (Which I had already changed).
The shop tech busted the slot out by using a small driver and not a coin slot driver. They also gouged the side of the puck getting it out of the mount.
I always send regs to the factory, ATOMIC Aquatics, since I do not trust the folks in the back room any more. I am a 36 year technician for a government agency that is known for precision.
If my techs skipped the torque wrench they would get a day with out pay.

 

[tflaris]

I just saw a post from a tech in which he said that although the manufacturers state recommended torques when assembling regulators, techs don't use torque wrenches when they are working. He was very clear regarding the general disregard for torqueing specs. He even stated that in his training class, the instructor told the students that no one uses torque wrenches in the real world.

Is this true? It's scary to me that manufacturer's specs would be widely ignored. Should I be concerned? Should I question my LDS about whether their techs bother using torque wrenches?

They are recommended by the manufacturer ScubaPro when repairing their regs. Yes I do.

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