Max. tightening torque for threaded collar
Max. tightening torque for threaded collar
(OP)
Hello everybody,
I am trying to calculate the max. allowed tightening torque of a threaded collar with given height and specified material and thread size (it is a metric, M10 thread). I have to put the specification of the max. admissible tightening torque on the single part drawing, so that the thread will not be damaged.
Normally, the requests are to calculate the tightening torque in order to obtain a specified pre-load, etc., but this is not the case.
Could anybody help me with an advice?
Thanks in advance for your answers.
I am trying to calculate the max. allowed tightening torque of a threaded collar with given height and specified material and thread size (it is a metric, M10 thread). I have to put the specification of the max. admissible tightening torque on the single part drawing, so that the thread will not be damaged.
Normally, the requests are to calculate the tightening torque in order to obtain a specified pre-load, etc., but this is not the case.
Could anybody help me with an advice?
Thanks in advance for your answers.





RE: Max. tightening torque for threaded collar
RE: Max. tightening torque for threaded collar
RE: Max. tightening torque for threaded collar
Any chance you could post a sketch with dimensions and material specifications?
desertfox
RE: Max. tightening torque for threaded collar
"how to calculate the max. torque rating" ... look up the spec
"standard tables for nut tightening torque" ... refer to the manufacturer's spec
"how to calculate the max. torque based on given data" ... any chance on giving us some tof the data ? the key would be if you are trying to achieve a required preload (unusual with a collar).
RE: Max. tightening torque for threaded collar
With this in mind, Mohr's Circle is applied in order to obtain the principle stresses imposed on the Pin with an applied torque equal to 75% material strength. You as the designer, would check for stress at the root of the thread, load through the threading (as a function of overall length) and at the thread reliefs if they are present in your design.
Ultimately the thread geometry and material selection govern the maximum applicable torque. You will find that your required torque for M10 alloy carbon steel thread is 77 N m (680 in lbf).
Hope this helps.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Max. tightening torque for threaded collar
The theory is the same. Good luck with it!
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Max. tightening torque for threaded collar
Of course, I am also grateful to desertfox and rb1957 for their answers. I attached a small drawing to be more clear about what I'm talking about.
RE: Max. tightening torque for threaded collar
DesertFox and RB1957 are both senior contributors and long time members to this forum. I would consider their input quite heavily, I find them well informed and in excellent command of subject matter.
Good luck with your design efforts.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Max. tightening torque for threaded collar
You mean I should consider only the thread shear and make the calculation based on that, not the combined case (shear and bend, von Misses)? Would it be realistic?
RE: Max. tightening torque for threaded collar
Looking at the sketch posted and using the Roymech site to obtain the shear stress area of the female thread per mm, (see link below)
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then muliply this obtained figure by the length of thread in the tapped hole to determine overall shear area, I get this:-
6.2mm * 21.479 mm^2/per mm
therefore shear area = 133.169mm^2 (female thread)
Now what we need to know is the grade of steel that the tapped hole is manufactured in or more to the point its allowable shear stress.
Multiply the allowable shear stress by the shear area above and that will determine the max allowable tensile load.
I am assuming that the screw or bolt is made from a much higher grade steel when compared to that of the tapped hole in which case the tapped hole will be the vunerable part.
desertfox
RE: Max. tightening torque for threaded collar
RE: Max. tightening torque for threaded collar
@CoryPad: this collar belongs to a support plate and it serves as a fixation point (a standard screw will be mounted in it, fixing this plate on a side-member), so no clamping of more parts together.
RE: Max. tightening torque for threaded collar
RE: Max. tightening torque for threaded collar
RE: Max. tightening torque for threaded collar
@dinjin: there is no risk of loosening in the system I have.
RE: Max. tightening torque for threaded collar
how are they going to conrol the application of the torque ?
is the idea to tighten till snug ?
if they strip a collar during manufacturing, is that a problem ?
RE: Max. tightening torque for threaded collar
RE: Max. tightening torque for threaded collar
The preload/installation torque is calculated based one 80% of material. The max torque that you want can be 100% of YS or even approaching material UTS. It is your choice as a design engineer.
Here is a online tools you may find useful:
http://www.futek.com/boltcalc.aspx?mode=metric
RE: Max. tightening torque for threaded collar
RE: Max. tightening torque for threaded collar
What I meant is that you can use the extractly same formula or equation to calculate the max or preload torques. Once you know how to do one, you can do another one fairly easy. But I agree they are two different values/things, one is breaking torque and another one is tightening torque.
romech is a great website. I believed I stole some formula from it before to develop some spreadsheet. But where is their torque calculator? I just checked their website and found formula, tables, but not the calculator where I can plug in thread diameter and material strength and then get tension preload and installation torque.