Do I need a torque screwdriver set?

[pc1966]

Unlike many years ago on most modern vehicles you find quite a lot of bolts are stretch bolts that are torqued to a set limit and are finished with an angular torque value

Certainly for the most critical ones for cylinder head, etc.

While using a torque wrench to get predictable forces is better than nothing it is not really that accurate. The wrench might be something like +/-3% in terms of torque applied, but that variability of friction on the threads and surface of the fasteners can make the resulting preload up to +/-30% variability.

With angle-tightening you take up the free play and then use the geometry of the thread to stretch/compress by a certain length which relates to the desired preload, though I believe it really only works well on long (w.r.t diameter) fasteners (like cylinder head studs, etc).

The 'feel' of tightening is another method that has been automated to get better results than torque, etc. For anyone who is interested here is a brief guide:

Methods of Tightening Threaded Fasteners

 

[Rockingit]

A better summary would be using a torque screw driver proves you complied with BS7671 which covers your --- in the event of a problem even it it was not your fault...

Rubbish. Possessing a torque driver shows no more compliance or competence to anything! Do you also think that owning a wardrobe of fancy clothes makes you more able to pull a model in a bar? Around my part of the world the local old-boys have a saying when a 'DFL' (Down From London) buys a house and jumps on the bandwagon of pretending to be a countryman - "All the gear and no idea", it's exactly the same with this.

Now, I've been NICEIC (and BSi before) inspected more times than I can remember and I have NEVER been asked to prove my competence by the contents of my tool box. Yes, MI's are to be followed and only practical way of doing that is with the right tool for the job - I'll give you that - but that's where the conversation ends! There are also hundreds of thousands of electrical items sold for installation in the UK where the flimsy instructions simply say to check all terminals for tightness and there are millions of consumer units perfectly safely installed years ago before this was even a thing. Do I own one? Yes, I do. Do I use it on every terminal I tighten, having scoured the web for downloads of MI recommended values?.......

I learned a saying when I was an apprentice from my old chief (who'd previously in HIS younger years assembled half the overhead grids in the South West) - "when it's white, it's tight" - referring to the fact that your knuckles go pale under proper stress.

 

[littlespark]

I live in Scotland. My whole hand is white, never mind my knuckles.

Sometimes goes pale blue when its a bit nippy... (you know, when we need to put a coat on)

 

[telectrix]

Yes, I'd be interested in your +/- thanks. If you still have them you'll have to let me know how we provide details to meet up. Appreciated

will do . i'll have a look later today.

 

[catdog1121]

Do you also think that owning a wardrobe of fancy clothes makes you more able to pull a model in a bar?

Nah Im an ugly old bugger, but I do reckon I'd have more chance of not being arrested for harassment if I wore clothes than if I tried to pull her and I was starkas..

Now, I've been NICEIC (and BSi before) inspected more times than I can remember and I have NEVER been asked to prove my competence by the contents of my tool box.

Really? First thing my assessor wanted to see is my approved voltage tester and lock off kit for safe isolation and the certificate to prove my MFT had been certified in the last year... I don't think they would have said I was competent if I didnt have an approved voltage tester and MFT (Of other testing devices to do the full range of tests)

Yes, MI's are to be followed and only practical way of doing that is with the right tool for the job - I'll give you that - but that's where the conversation ends! There are also hundreds of thousands of electrical items sold for installation in the UK where the flimsy instructions simply say to check all terminals for tightness and there are millions of consumer units perfectly safely installed years ago before this was even a thing. Do I own one? Yes, I do. Do I use it on every terminal I tighten, having scoured the web for downloads of MI recommended values?.......

Don't disagree with you one bit, why do you think they put on their check all the terminals for tightness? Surely they the manufacturer can do up a terminal to the correct tightness? Its to shift the blame if in the unlikely chance something were to go wrong.. That is my who point, not having a torque screwdriver and not following instructions opens you up to being instantly put at blame.. Its like if your drunk while driving and some silly bugger pulls out right in front of you.. Even though it might be their fault for pulling out, it will be yours because your drunk..

I learned a saying when I was an apprentice from my old chief (who'd previously in HIS younger years assembled half the overhead grids in the South West) - "when it's white, it's tight" - referring to the fact that your knuckles go pale under proper stress.

Yep thats pretty good, and I can understand people who might have been doing it for years don't see the point, I am sure when MFT and more rigorous testing came in there was some electricians back in the day saying why do I need to spend all this money on a testing device, I know what I am doing, I dont make mistakes.

 

[littlespark]

They put the torque setting on a sticker inside the CU usually. It must be there for a reason.
Not hidden away in the paperwork somewhere.

They may need to change the “ensure all connections are tight” label to something that mentions torque… that might bring more people into using them.

The only people that should be inside a CU are electricians, and if they all have a torque driver, then there will be no excuse for too loose or too tight connections.
Can it become a “service” like vehicles where we check that terminations are still torqued to the correct value… and CU’s sealed like a meter to detect tampering?

Random thoughts for a Friday night

 

[Dustydazzler]

Which then begs the question , Do you re-torque every 5 or 10 years when doing the Eicr or once torqued up initially is that good enough for the life of the unit ?

 

[littlespark]

Which then begs the question , Do you re-torque every 5 or 10 years when doing the Eicr or once torqued up initially is that good enough for the life of the unit ?

It would have to be checked frequently, as we all know, screw terminals can loosen simply with high load cycling as well as physical vibration.


Just trying to drum up some business for us guys

 

[Dustydazzler]

It would have to be checked frequently, as we all know, screw terminals can loosen simply with high load cycling as well as physical vibration.


Just trying to drum up some business for us guys

Re-torque annually ?

 

[littlespark]

Re-torque annually ?

Bi-annually.

Every 6 months, with a calibrated torque driver.
Just the CU terminations. More paperwork, with a list of every screw…. Serial numbers,
Optimum settings….


Most CUs start falling apart after taking the cover screws off twice, never mind for the lifetime of the equipment.

 

[telectrix]

think this thread has been torqued about enough now. mods please close with a zipper tightened to 5Nm ( weird measurement as Newton died long before the metric system was invented by the french rabble who'd just chopped the heads off all the intelligensa.

 

[LewisM]

Make all connections like hi loks that we use in aviation that snap off at a certain torque, can't be under or over tightened

 

[Dustydazzler]

Make all connections like hi loks that we use in aviation that snap off at a certain torque, can't be under or over tightened

How would you disconnect to do periodic testing ?

 

[LewisM]

How would you disconnect to do periodic testing ?

I was only messing would never work as you say for testing etc and knowing my luck I'd put the wrong cable In the wrong breaker then it would be too late

 

[Mike Johnson]

Always makes me smile when the comments turn to the whole family died in a fire caused by not conforming to ....................whatever, if the family died I would think the house was a right off and the consumer unit and electric circuits/cables destroyed along with the house, how is anyone going to know if anything conformed or was complied with prior to the fire or who is too blame, fire investigations officer's can only go so far, and I don't think they are clairvoyant.