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Have you checked your torque wrench calibration?

Posted By: Calypso Red

Have you checked your torque wrench calibration? - 15/11/19 08:40 PM

I sucessfully changed my 4/4 cambelt, a feeling of smug satisfaction.

A few days later I came across a YouTube video, 'How to calibrate your torque wrench'.
https://www.youtube.com/watch?v=XaqBA-xSGbc

Out of curiosity I checked my large torque wrench, 60 - 220ftlbs, which was spot on. However, when I checked my small torque wrench, 10 - 80ftlbs, which I have had for about 10 years, I found it was 'clicking' at a value approximatly 25% below the set value. There are videos on YouTube which show how to reset a torque wrench, so now, it is spot on.

Then I realised I had a problem! My small torque wrench is very useful for the low values required when working on an aluminimum engine and I had used it for the majority of the cambelt change. 10 -15% error I could live with but not 25% when a cambelt is involved. So yes, I took it all apart and put it back together again, with the correct torque values.

The learning point, 'It pays to calibrate your torque wrench now and again' frown2
Posted By: BobtheTrain

Re: Have you checked your torque wrench calibration? - 16/11/19 09:42 AM

Interesting. "Every day is a school day".
Posted By: Arwyn Williams

Re: Have you checked your torque wrench calibration? - 16/11/19 10:02 AM

Yes, once a year and always just before I rebuild an engine. It helps that my neighbour can get them recalibrate and certified.

How many people know there is a correct way to store a torque wrench?

Arwyn
Posted By: Hamwich

Re: Have you checked your torque wrench calibration? - 16/11/19 10:11 AM

Although I have a torque wrench (which I do store correctly, fully slackened) I find often I just use an electronic fish scale (like that used in the video) to apply a measured amount of torque. Hook it into the end of a ring spanner, measure the distance, and it's easy to calculate the correct weight to pull at. Very handy when a full size torque wrench can't be brought to bear.
Posted By: Luddite

Re: Have you checked your torque wrench calibration? - 16/11/19 10:16 AM

Torque wrench...? I was taught that the size of bolt, the material used and the thread type, alongside the likely spanner weight and length averaged out one`s expectations on how much pressure to apply when tightening things....?

But in more advanced engineering terms, I ever park my torque wrench with it wound right back taking pressure off the spring... smile
Posted By: Ian Wegg

Re: Have you checked your torque wrench calibration? - 16/11/19 10:41 AM

Certainly an entertaining video! He needs to do a follow up on how to recalibrate your luggage scale, perhaps by weighing a litre of water at 4 degrees C? Then another one on how to recalibrate your thermometer ... hide
Posted By: Hamwich

Re: Have you checked your torque wrench calibration? - 16/11/19 10:52 AM

Originally Posted by Luddite
Torque wrench...? I was taught that the size of bolt, the material used and the thread type, alongside the likely spanner weight and length averaged out one`s expectations on how much pressure to apply when tightening things....?


I read somewhere of a study that demonstrated that for fasteners tightened without a torque wrench, the vast majority of small sizes were over-tightened, and the vast majority of larger sizes were under-torqued.

I was amazed when I did the cambelt on my Ecotec engine. Because it has variable cam timing I decided to replace the cam wheels at the same time as they have internal oil ways and gubbins to do the phase change. There are no keyways or detents on the cam shafts, the wheels are just dialled into position and locked on to the taper with torque, about 95 ft-lb if memory serves. You certainly wouldn't want to get that wrong by under-tightening and having them come loose! :-)
Posted By: stefan s

Re: Have you checked your torque wrench calibration? - 16/11/19 11:00 AM

V good tip .Going to check.

Stefan
Posted By: Richard Wood

Re: Have you checked your torque wrench calibration? - 16/11/19 11:03 AM

The first time I used a torque wrench on small bolts, in this case for split brake caliper, I was surprised how much torque was physically needed - way more than I would have naturally used for the size of bolt.

ETA: On the other hand, an old school Rolls Royce trained engineer once told me they were only issued with short open end/ring spanners to avoid over-tightening.
Posted By: Luddite

Re: Have you checked your torque wrench calibration? - 16/11/19 12:03 PM

Ian... you omitted to suggest checking at what temperature one`s steel rule would be accurate.... unless it was made of invar.. (-:

No argument from me as to the value of a torque wrench..... provided it has an in date calibration certificate...(-:
Posted By: Gambalunga

Re: Have you checked your torque wrench calibration? - 16/11/19 01:43 PM

You learn something every day smile

My only criticism was that he put the socket in a vice without using a set of soft jaws nono
Posted By: IvorMog

Re: Have you checked your torque wrench calibration? - 16/11/19 05:04 PM

Good advice.

Remember also that bolts should be lightly lubricated with thin machine oil (such as 3in1) or the torque applied will not translate fully into clamping force.

This is because on a dry bolt some of the torque is lost in the friction of the thread before it gets to the full clamping load.

PS. Don't forget my Cam TDC tools somestick
Posted By: RedThree

Re: Have you checked your torque wrench calibration? - 16/11/19 08:00 PM

Have access to the torque checking machine at work that gets calibrated annually so from time to time I do check.
Posted By: Cat302

Re: Have you checked your torque wrench calibration? - 16/11/19 09:11 PM

Calibration of tools is always good practice. No need to place a socket in a vice, the socket will be very unhappy, just grip the square drive in your vice using soft jaws. I was always taught to use a molycote type grease on screw threads, this to ensure the delivered force is presented as a clamping force and not reduced due to frictional loss of the male female threads and shoulder contact.
Posted By: BobtheTrain

Re: Have you checked your torque wrench calibration? - 16/11/19 09:54 PM

We use a "spider" for cable testing. It consists of 19 wires pot-soldered together at one end, crocs on the other end of 18 of them and a banana plug on the last one. Believe it or not, it has to get calibrated to Network Rail's standards! That is in the real world, however, in a training environment we just ask the candidates what they would check on the spider. (Calibration and continuity).
Posted By: BobtheTrain

Re: Have you checked your torque wrench calibration? - 16/11/19 09:55 PM

Originally Posted by Gambalunga
My only criticism was that he put the socket in a vice without using a set of soft jaws nono

Hear! Hear!
Posted By: Calypso Red

Re: Have you checked your torque wrench calibration? - 16/11/19 11:19 PM

Originally Posted by IvorMog

PS. Don't forget my Cam TDC tools somestick


They are already in the bag and ready to go! notworthy
Posted By: ChrisConvertible

Re: Have you checked your torque wrench calibration? - 17/11/19 11:32 PM

A good reason to keep that worn out socket.

I did mine a different way. I put the torque wrench in the vise sticking out and vertically hanging down rather than horizontal. I didn't use a socket, just the square in the vice with soft metal to protect it. I measured 2 foot on my particular wrench and marked it on tape. Used a 16kg kettle bell to gently hang off the tape at the mark with the torque wrench set to 70foot lb and heard it click, then put it to 71 and heard it not click so was happy as 16kg is 35.2lb and needed to be 70.4pounds at two feet. So my wrench will click somewhere between 70 and 71 and 70.4 is pretty well in the middle.

I think I prefer my method as his means having to look at the scale that is not that steady as he pulled on it.
Posted By: Jads

Re: Have you checked your torque wrench calibration? - 20/11/19 05:48 PM

I fully agree with Cat302 regarding regular calibration of tools, in fact I re-calibrated my hammer just this morning !!!!
Posted By: Deejay

Re: Have you checked your torque wrench calibration? - 21/11/19 07:39 AM

Originally Posted by Jads
I fully agree with Cat302 regarding regular calibration of tools, in fact I re-calibrated my hammer just this morning !!!!

You can’t beat being thorough...I mean, that’s really hitting the nail on the head!!
Posted By: Calypso Red

Re: Have you checked your torque wrench calibration? - 21/11/19 07:53 AM

Originally Posted by Jads
I fully agree with Cat302 regarding regular calibration of tools, in fact I re-calibrated my hammer just this morning !!!!


That's true 'Percussion Engineering'.
Posted By: Cat302

Re: Have you checked your torque wrench calibration? - 21/11/19 08:34 AM

[quote=Jads]I fully agree with Cat302 regarding regular calibration of tools, in fact I re-calibrated my hammer just this morning !!!!

If you have an assistant with you when calibrating your hammer, Never say “ When I nod my head, hit it”
Posted By: sospan

Re: Have you checked your torque wrench calibration? - 21/11/19 11:20 AM

Ah! The world of accuracy and calibration.
How far do you go? How accurate do you NEED to be?
Memories from my QC days!
I remember weighing equipment used and having to satisfy HMRC re tobacco duty payments.
Accuracy to 2 dec. places and a certified calibration regime with full documentation and procedure.
Mind you some of the HMRC desk jockeys were hard work. Trying to explain the niceties of sampling plans, accuracy, calibration routines was exasperating.
Anyway, this weekend is our Taffmog Christmas weekend at Ardencote Manor Hotel near Warwick (why stay local when you can travel and enjoy different areas ....Dawlish setup for 2020) so I will check my torque wrench when back.
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