Every Screw Max Torque Chart is Different!

[rg12]

https://www.boltdepot.com/fastener-information/bolts/Metric-Recommended-Torque.aspx
https://www.engineeringtoolbox.com/metric-bolts-maximum-torque-d_2054.html
http://electronicfilters.tpub.com/TM-10-4330-237-13P/css/TM-10-4330-237-13P_105.htm
https://www.coastalfasteners.co.nz/torque-data

Am I crazy or there should be some kind of a standard?
Also, how can there ever be a standard when every screw and every thread is different?
Different screw material, different thread material, different bolt length(?), what about helicoils?

 

[DogDipstick]

There are many standards, Rg12. Because there are many variables.

Engineers who design the assy are the ones to spec the fastener tourque.

There is a standard for every service required.

Some are Acme, some are Whitworth, 60* threads, square threads... some are SAE, ect.

Pitch makes a big difference ( think, ramp)... in the stress/strain of a fastener.... depending on the applied tq. .... and the lubrication condition. Use oil on one bolt, and Moly on the next.... and the bolt might break with Moly on the threads with the same tq that it was specced for tq coated in oil.

You could become an engineer, then you would have your standard.

Or I could give you a (excell) spreadsheet written by my father who was hired by a company, Holtech Int., to spec the bolts on their nuclear power plant containment and reactors...

.... I have the software program that takes (type of ) material, (thread )type, pitch, and applied tq into the eq. written by a ASME member for the most critical bolt fastening on the planet, if you are up to that level of completeness and competency, I could sent you the program ( EXCELL), written by this engineer and used in hundreds of nuke plants round the world....

Honestly, the generic charts work fine, just look out for egregious typing misprints, like "Ft" where "In" should have been in "inch lbs". That will break your bolt faster than a manhandler wrench with a doffus on the end .

For me, if the fastener has enough bite, the locktite does its job.

 

[rg12]

There are many standards, Rg12. Because there are many variables.

Engineers who design the assy are the ones to spec the fastener tourque.

There is a standard for every service required.

Some are Acme, some are Whitworth, 60* threads, square threads... some are SAE, ect.

Pitch makes a big difference ( think, ramp)... in the stress/strain of a fastener.... depending on the applied tq. .... and the lubrication condition. Use oil on one bolt, and Moly on the next.... and the bolt might break with Moly on the threads with the same tq that it was specced for tq coated in oil.

You could become an engineer, then you would have your standard.

Or I could give you a (excell) spreadsheet written by my father who was hired by a company, Holtech Int., to spec the bolts on their nuclear power plant containment and reactors...

.... I have the software program that takes (type of ) material, (thread )type, pitch, and applied tq into the eq. written by a ASME member for the most critical bolt fastening on the planet, if you are up to that level of completeness and competency, I could sent you the program ( EXCELL), written by this engineer and used in hundreds of nuke plants round the world....

Honestly, the generic charts work fine, just look out for egregious typing misprints, like "Ft" where "In" should have been in "inch lbs". That will break your bolt faster than a manhandler wrench with a doffus on the end .

For me, if the fastener has enough bite, the locktite does its job.

Thanks man but I just need a general idea, maybe a range for each common bolt and will just "feel it" from there and have all the bolts torqued the same.
I need it for matching tightness all around and for not stripping a thread more than not having the bolt go loose which never happens as I do use locktite wherever needed.

 

[Punx0r]

Your first link will do fine and is the simplest.

Metric bolts are easy because they have the grade (strength class) e.g. 8.8 stamped onto the head.

8.8 is your standard bolt and most likely what you'll be using. You might see 10.9 or maybe 12.9 if you're specifically buying high tensile bolts.

The charts all vary a bit because the coefficient of friction on the bolt threads makes a big difference to the required torque, so it depends what bolts were tested to produce a particular table. Oiled or not, plain steel, zinc plated, nickel plated, galavanised etc.

The default is BZP coated (bright zinc plating). If you buy silver coloured bolts this is almost certainly what you'll get and the above tables will work fine. Watch out for stainless though - they have different torque specs.

The figures in those tables have a margin of safety. Torque to break will be roughly 50-100% more unless oiled/greased/waxed.

If you ever find a bolt turning but not getting tighter any more then stop because it's yielding. It's not ruined, but it's your warning that if you keep turning it will suddenly snap. If you have a greased bolt this can occasionally happen below the normal torque spec. Just something to be aware of - you develop a feel for it after a while.

 

[serious_sam]

It's funny because it's true.

As mentioned in posts above, any of those tables are fine.

Just be careful what you're screwing the bolt into. If it's the equivalent grade/class nut, then no problem. If it's some cheap threaded aluminium component, then you may want to reduce that torque figure significantly.

Also, loctite will act as a lubricant, so also take that into consideration.

Friction and % of proof stress are the 2 variables that cause the differences in the tables that you listed.

On a detailed level it gets ridiculous, even for simple joints. Have a read of VDI 2230-1.
https://www.fsb.unizg.hr/miv/MSUI/KonMot/KonMot_2014/VDI 2230-1 (2003.02) Schraubenverbindungen.pdf

 

[DogDipstick]

Actual screenshot of the good fastening torque and the forces involved.



No for real, here is a screenshot. It gets really complicated. I mean really, really silly complicated complicated IMO. All kinds of numbers here and there... .. you know math stuff. Just to calculate the forces in a wedge or something. Lol.

Its a very interesting spreadsheet. Lol. As for how spreadsheets go.. yeah.

IMO just look out for tearing threads in the hole material, how good the threads are cut and how much depth. IDK how many times Honda or Kawa bolts were mismatched to diffent holes in the case covers of the engines, but if you put a short bolt into a long hole dont expect it to hold, nor not ruin the block. Or snapping lil fasteners thinking it is critical but it is not. I have found it is easier to fasten twice, locktyite,or lockwire, than replace teh things being fastened.

 

[rg12]

Actual screenshot of the good fastening torque and the forces involved.

CATLADDER.jpg

No for real, here is a screenshot. It gets really complicated. I mean really, really silly complicated complicated IMO. All kinds of numbers here and there... .. you know math stuff. Just to calculate the forces in a wedge or something. Lol.

Its a very interesting spreadsheet. Lol. As for how spreadsheets go.. yeah. threadtqs4.gif

IMO just look out for tearing threads in the hole material, how good the threads are cut and how much depth. IDK how many times Honda or Kawa bolts were mismatched to diffent holes in the case covers of the engines, but if you put a short bolt into a long hole dont expect it to hold, nor not ruin the block. Or snapping lil fasteners thinking it is critical but it is not. I have found it is easier to fasten twice, locktyite,or lockwire, than replace teh things being fastened.

Damn that's alot of science right there...
Am gonna stick with the general idea provided by the charts plus some common sense using my natural feel and go from there.

Thanks alot guys!