How do you torque???

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Jerry D.

Jerry D.

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Any mechanics out there with a technical opinion???

For years I have always looked at most torque specs to read a “range”. In the FSM and other similar publications, there is almost always a “range” indicated. Such a 75~95 ft/lb as being able to select from 75 ft/lb as being the minimum torque for the fastener to work properly, up to 95 ft/lb being the maximum for the fastener before it could be compromised and perhaps fail. And of course there are many specs with only a single torque given.

Now a friend has said that in the military training, they are told that the lower number is a “first torque” for all the fasteners on that particular part, and then increase all of the fasteners to the upper torque for the final set. So saying this is not a “range”, it is a pre-torque and then the final torque.

I have not been able to locate any definite information on which is correct. I just personally believe that the books/manuals give the numbers as a “range”, and as long as each is torqued evenly on any given part, all is well and happy.

Have I been wrong, or could the military be different???

Thanks,
Jerry D.
 
Yeah, I think you're correct. With things like head bolts and such, its a good idea to never torque straight to spec. In other words, do waves building up to the torque spec. Of course, if its an oil pan gasket bolt, you go straight to its cause its like 8 ft-lb.

Good luck
 
Or until your Crapsman clicker torque wrench gives up the ghost and you discover that the lifetime warranty is not-so-much on anything with an internal mechanism any more complicated than a ratchet. But hey, they might repair it as a "calibration", which is only 1.5x the price of a new wrench. :crybaby:

We used the military method described above when I was in, but now I just shoot for mid-range on any given torque spec and then recheck it x number of miles/hours later...
 
Her'e my 2c worth.

When torquing bolts where there are multiple bolts and the item being secured can warp (eg. Cylinder head or engine sump), then it is important to torque them gradually and in the correct sequence.(Working from the centre outwards - A bit like flattening out a crumpled sheet of paper.)

But to answer you're question - I believe when a range is given, the manual is saying that a final torque anywhere in that range is OK.

So please yourself whether you choose the high end or the low end or somewhere inbetween. (I favour "just above the lower end" mostly.)

From my experience, you need to beware though. Don't allow the manual's torque specification to over-ride your own good judgement. When I thought the manual was "gospel" I once tried torquing a bolt that was threaded into alloy to the torque spec printed clearly there (in my manual) and stopped only when I felt the threads beginning to giveway. (The manual does have errors!)

:cheers:
 
Now that I think about it, I've been bitten by that as well. I was using tha torque spec for the later driveline bolts on my Oct '67 40 ('67 drivetrain with '68 body) and mushed two of them before stepping back and regrouping. Having a transitional year rig is fun! ;p
 
lostmarbles said:
Her'e my 2c worth.

When torquing bolts where there are multiple bolts and the item being secured can warp (eg. Cylinder head or engine sump), then it is important to torque them gradually and in the correct sequence.(Working from the centre outwards - A bit like flattening out a crumpled sheet of paper.)

But to answer you're question - I believe when a range is given, the manual is saying that a final torque anywhere in that range is OK.

So please yourself whether you choose the high end or the low end or somewhere inbetween. (I favour "just above the lower end" mostly.)

From my experience, you need to beware though. Don't allow the manual's torque specification to over-ride your own good judgement. When I thought the manual was "gospel" I once tried torquing a bolt that was threaded into alloy to the torque spec printed clearly there (in my manual) and stopped only when I felt the threads beginning to giveway. (The manual does have errors!)

:cheers:
Click to expand...


Glad I found this.

I was torquing to the lower number first then the higher number. Then I realized I was reading my wench wrong and redid them again.

So this will be the third time I attempt torquing the first stages of the engine rebuild.

Good stuff

I have dismantled everything and will follow this advice.
 
Many older torque specs where written for beam - type torque wrenches where accuracy was subject to operator error. All torque wrenches are subject to environmental conditions, wear, age, use of extensions, etc. Users need to account for these factors (among others) to end up within a specific 'range' . When was the last time anyone here had the manufacturer recalibrate their torque wrench. :-)
 
Not that anyone cares, this being such an old thread, I thought I would add some insight from FAA AC43.13 (for aircraft mechanics)-

7-40. TORQUES. The importance of correct torque application cannot be overemphasized. Undertorque can result in unnecessary wear of nuts and bolts, as well as the parts they secure. Overtorque can cause failure of a bolt or nut from overstressing the threaded areas. Uneven or additional loads that are applied to the assembly may result in wear or premature failure. The following are a few simple, but important procedures, that should be followed to ensure that correct torque is applied. NOTE: Be sure that the torque applied is for the size of the bolt shank not the wrench size. a. Calibrate the torque wrench at least once a year, or immediately after it has been abused or dropped, to ensure continued accuracy. b. Be sure the bolt and nut threads are clean and dry, unless otherwise specified by the manufacturer. c. Run the nut down to near contact with the washer or bearing surface and check the friction drag torque required to turn the nut. Whenever possible, apply the torque to the nut and not the bolt. This will reduce rotation of the bolt in the hole and reduce wear. d. Add the friction drag torque to the desired torque. This is referred to as “final torque,” which should register on the indicator or setting for a snap-over type torque wrench. e. Apply a smooth even pull when applying torque pressure. If chattering or a jerking motion occurs during final torque, back off the nut and retorque. NOTE: Many applications of bolts in aircraft/engines require stretch checks prior to reuse. This requirement is due primarily to bolt stretching caused by overtorquing. f. When installing a castle nut, start alignment with the cotter pin hole at the minimum recommended torque plus friction drag torque. NOTE: Do not exceed the maximum torque plus the friction drag. If the hole and nut castellation do not align, change washer or nut and try again. Exceeding the maximum recommended torque is not recommended. g. When torque is applied to bolt heads or capscrews, apply the recommended torque plus friction drag torque. h. If special adapters are used which will change the effective length of the torque wrench, the final torque indication or wrench setting must be adjusted accordingly. Determine the torque wrench indication or setting with adapter installed as shown in figure 7-2.


AC 43.13 has a lot of useful information about standard practices for aircraft mechanics as well as any mechanic. All the information in there of course will not be applicable to a car mechanic, but there is something to be gleaned from it. It's available free on the FAA website under advisory circulars.
 
As an aircraft mechanic signing off aircraft, my torque wrench is calibrated once a year. Not necessarily by the manufacturer, but by the local cal shop.
 
Had not noticed the date of the last reply. Talk about a revival.

Thanks for that info.
 
emtee said:
Now that I think about it, I've been bitten by that as well. I was using tha torque spec for the later driveline bolts on my Oct '67 40 ('67 drivetrain with '68 body) and mushed two of them before stepping back and regrouping. Having a transitional year rig is fun! ;p
Click to expand...

I see this member hasn't posted in a while. Would have been interested in his VIN. I have a 9/67 production most of my drive train is 68. Drivelines were small bolts and coarse spline axles with ball and claw in the front.

The FSM shows the order for tightening head bolts. Tighten the wrong way could ruin a brand now head gasket so it leaks. No mechanic but would thing warping the head isn't out of the question. Even lug nuts I tighten in steps and use a pattern that rotates back and forth.
 
Not a certified mechanic but i've been wrenching on cars and motorcycles for more than 45 years. Some of the things I've learned over this time are don't torque a bolt or nut more than 90 degrees after it has full contact or risk failure. Torque wrenches help prevent you from having to use EZ Outs or replace broken hardware because of a heavy hand. I usually shoot for the middle torque value given that even the best torque wrenches seem to have a 4% error factor. Knowing this and given that torque wrenches are usually spring controlled means that the springs soften over time and actual torque value will be lower than indicated on the wrench. Torque wrenches are more accurate in the middle of their range so try and choose the drive size that puts you in this range. Critical parts, meaning anything that a manufacture lists a torque value for mean try and comply with that value. If there is something that prevents you from using a torque wrench fall back to the never past 90 degree turn past full contact rule.

Everyone has a different feeling for what is snug and what is tight, torque wrenches try and minimize the affect of the gorilla affect. :)
 
B y r o n said:
torque wrenches try and minimize the affect of the gorilla affect. :)
Click to expand...
Haha. Resident gorilla here... It's not tight enough! Snap :censor:
 
Shoot for the middle of the range-it's a tolerance. Allows for variables in the type tools used/etc. In production (diesel engine parts) mostly done with hydro-pneumatic torque tools-Expensive, usually air powered gun/nutrunner/etc type tools-some manual click-type. All types of tools used depending on what works best for the joint/ergonomics/etc. Some auto-shutoff-some auto-reverse. Some not. Watched production parts being torqued for years and seemed to be about a 20% tolerance on lots of torque specs. When QC spot checked later just had to be in that range. All tools regularly calibrated/certified. QC had electronic tools with transducers all regularly certified. Every fastener had a torque spec.
 
It depends.

Some Toyota's (and usually it's called out) will actually have a step value if it's meant to be stepped. If you see, for instance, 45 ft/lbs + 90 + 90... this is a 3 step process where you set all bolts to 45 ft/lbs and then torque (in the same order) 90* each pass (2 passes).

MOST bolts... I don't torque to value. Depending on the size of the bolt (or use) I will vary how tight I actually enter it. Most things the torque value isn't all that important - but internal engine, transmission, differential (etc) are.

Setting the torque value on that oil pan bolt, for instance, isn't all that important so long as you're able to be pretty consistent.
 
Keep in mind also, that ANYTHING added to the nut/bolt such as anti-seize or thread locker will change the torque value, and in this case a "wet" torque value should be used to prevent over torquing. (The addition of these compounds reduces the friction, thus making it easier to turn - a lower end value will result in the same holding power.
 
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