4 ms·

My beef is that torque specs are for factory assembly. If you’re using new parts, sure, but once they’re old/re-used parts with some corrosion due to dissimilar

My beef is that torque specs are for factory assembly. If you’re using new parts, sure, but once they’re old/re-used parts with some corrosion due to dissimilar metals, age or salt belt, you’re flying blind and probably undertorquing if going by the book. Given the amount of (soft) aluminum on aircraft, (737 is 80% aluminum), it would be insane to not precisely consider torque. Steel on steel is more forgiving.

lucisferre 3y ago
Why would the softness matter for torque, if there has been some shift or compression since original install the torque should still ensure the correct pressure between the fitting, no?
- Scoundreller 3y ago
  That’s assuming then original install torque spec was correct. Much easier to strip aluminum threading if you over torque. Steel tends to just bend (and bend back better). Aluminum also fractures while steel bends/stretch back and forth better. (This is mainly from my experience working on bicycles, and a little auto)
- etrautmann 3y ago
  A major concern is presumably over-torquing a screw and causing partial failure of threads in the material. This could be subtle and difficult to detect, but present as a problem over time.
- kube-system 3y ago
  Soft materials develop wear more easily. e.g. any slight boogering of the threads of a used fastener could translate into rotational torque that doesn't end up being converted to a clamping force. (or in more extreme instances, some fasteners are torque to yield, and change shape after their first use, and must be replaced. But I'll presume that's not what they were talking about here)
- lupusreal 3y ago
  Aluminum has no fatigue limit, so you really need to do things by the book.
the_third_wave 3y ago
> If you’re using new parts, sure, but once they’re old/re-used parts Most service manuals require new bolts, fasteners and washers for torque-critical parts.
- HPsquared 3y ago
  Skipping that part is even more ubiquitous than failure to properly torque. It takes a lot of effort to buy the correct bolts, only specialists have them to hand for a given make. Even dealers might not have every bolt. So it means you need to procure many more parts you would otherwise (the part you're replacing, plus 20 specific bolts with part numbers).. Most mechanics don't bother unless it's something really big like cylinder head bolts or an axle nut.
  - the_third_wave 3y ago
    That is probably valid reasoning when talking about a neighbourhood mechanic dealing with all brands but it does not hold for an aircraft maintenance shop. Skipping this step makes them liable for any problems caused by failure of related parts so I assume [1] they keep to the book in this respect. Anyone here who has experience with one of these shops want to chime in? When I work on machinery I tend to follow the rules when dealing with stretch bolts since these do tend to fail far more often when re-torqued but for normal (non-stretch) bolts I do often reuse them if they're in good enough shape. I work mostly on farming/forestry equipment and our personal vehicles though, not on airplanes. [1] which makes an ass (out of) u (and) me
- deleted 3y ago
  [deleted]

lucisferre 3y ago

Why would the softness matter for torque, if there has been some shift or compression since original install the torque should still ensure the correct pressure between the fitting, no?

Scoundreller 3y ago
That’s assuming then original install torque spec was correct. Much easier to strip aluminum threading if you over torque. Steel tends to just bend (and bend back better). Aluminum also fractures while steel bends/stretch back and forth better. (This is mainly from my experience working on bicycles, and a little auto)
etrautmann 3y ago
A major concern is presumably over-torquing a screw and causing partial failure of threads in the material. This could be subtle and difficult to detect, but present as a problem over time.
kube-system 3y ago
Soft materials develop wear more easily. e.g. any slight boogering of the threads of a used fastener could translate into rotational torque that doesn't end up being converted to a clamping force. (or in more extreme instances, some fasteners are torque to yield, and change shape after their first use, and must be replaced. But I'll presume that's not what they were talking about here)
lupusreal 3y ago
Aluminum has no fatigue limit, so you really need to do things by the book.

the_third_wave 3y ago

> If you’re using new parts, sure, but once they’re old/re-used parts Most service manuals require new bolts, fasteners and washers for torque-critical parts.

HPsquared 3y ago
Skipping that part is even more ubiquitous than failure to properly torque. It takes a lot of effort to buy the correct bolts, only specialists have them to hand for a given make. Even dealers might not have every bolt. So it means you need to procure many more parts you would otherwise (the part you're replacing, plus 20 specific bolts with part numbers).. Most mechanics don't bother unless it's something really big like cylinder head bolts or an axle nut.
- the_third_wave 3y ago
  That is probably valid reasoning when talking about a neighbourhood mechanic dealing with all brands but it does not hold for an aircraft maintenance shop. Skipping this step makes them liable for any problems caused by failure of related parts so I assume [1] they keep to the book in this respect. Anyone here who has experience with one of these shops want to chime in? When I work on machinery I tend to follow the rules when dealing with stretch bolts since these do tend to fail far more often when re-torqued but for normal (non-stretch) bolts I do often reuse them if they're in good enough shape. I work mostly on farming/forestry equipment and our personal vehicles though, not on airplanes. [1] which makes an ass (out of) u (and) me
deleted 3y ago
[deleted]