Threaded Fasteners - Bolt - Torque Specs

[dank]

Found this site to be useful when hunting down torque specs for various bolts.

http://www.torqwrench.com/Info/fasteners.php

[zagan]

Some of the metric bolts have a number on them and that's the torque that is meant to be applied.

Like the 16mm bolts we have they have an 8 on them.

[dogbreath_48]

Some of the metric bolts have a number on them and that's the torque that is meant to be applied.

Like the 16mm bolts we have they have an 8 on them.

I believe the number on the head refers to the grade of material used. The tensile strength of the bolt, and hence the max torque to be applied could be derived from this.

-Stu

[dank]

Yeah ur right stu.

Going by the chart a grade 8.8 10mm bolt should be done up to 606kg.cm or 43.8ft.lbs.

My dilemma is though, i've torqued up my crankshaft to flexplate bolts to "manufacturers specs" which is 54ft.lbs and it seems like its too loose. Maybe I've just been overtightening things my whole life??

Have used locktite medium strength on them so they should never work loose anyway. Using a torque wrench with a longer handle than my regular socket wrench might be messing with my brain and what i "think/feel" like might be the right tightness. who knows....time will tell i guess.

[sudso]

Some of the metric bolts have a number on them and that's the torque that is meant to be applied.

Like the 16mm bolts we have they have an 8 on them.

x2
Jap cars bolts have numbers on them to reference to the torque value stated in the service manual for that vehicle.
EG: different size diameter bolts may have the same number but when you refer to the manual there are different torque settings for the different size bolts even though they may have the same number.

[sudso]

Some of the metric bolts have a number on them and that's the torque that is meant to be applied.

Like the 16mm bolts we have they have an 8 on them.

I believe the number on the head refers to the grade of material used. The tensile strength of the bolt, and hence the max torque to be applied could be derived from this.

-Stu

The grade of bolt has nothing to do with the torque setting of the bolt in its application.
Most motor thread bolts have numbers on them that refer to the torque setting stated in the manual for that vehicle for that particular size bolt.
Numbers such as 4.6 or 8.8 are steel grades not torque. Its different for every size bolt and application.

[dogbreath_48]

My dilemma is though, i've torqued up my crankshaft to flexplate bolts to "manufacturers specs" which is 54ft.lbs and it seems like its too loose. Maybe I've just been overtightening things my whole life??

It can be surprising how 'loose' most fasteners are meant to be. I've never been one to severely over torque - but i must have usually been a fair whack tighter than spec.

Makes me wonder what damage serious over-tighteners are doing to their bolts, studs and components!

-Stu

[Pyrotech]

My dilemma is though, i've torqued up my crankshaft to flexplate bolts to "manufacturers specs" which is 54ft.lbs and it seems like its too loose. Maybe I've just been overtightening things my whole life??

i thought the same thing when i rebuild my sierra engine, im like, hmmm, shouldnt they really be tighter then that?. but the FSM says otherwise

[KiwiBacon]

The grade of bolt has nothing to do with the torque setting of the bolt in its application.
Most motor thread bolts have numbers on them that refer to the torque setting stated in the manual for that vehicle for that particular size bolt.
Numbers such as 4.6 or 8.8 are steel grades not torque. Its different for every size bolt and application.

The grade of the bolt and the size of the bolt determine what torque range can be used, the application determines what is best.

All the bolts in my japanese diesel engine have the grade cast into the top of them. Grade 7, grade 9 etc.
While a service manual may indicated (grade 9, m10 torque to xNm) that is based on the strength of the bolt, it is not a manufacturer specific code.

[Yo_jono]

Look at

www.norbar.com

[ISUZUROVER]

but the FSM says otherwise

I didn't realise the Flying Spaghetti Monster was an expert on bolt torque? But I suppose he is all knowing and all powerful.

[Patroler]

Had a guy at work asking me about various turque settings for different sized bolts, he was trying to work out how tight his sump plug should be on his GSXR 1000 , i replied that i don't think you'll ever shear a sump plug in that application - it is after all a 14mm bolt (fine thread) into an aluminium pan - wonder what will let go first!
Just do the thing up until it seats and then a fraction more - I would think a fitter in his 40's would know how tight by feel!
Same thing with oil filters - i can remove any of mine by hand - just, never had one loosen - ive got a reasonable grip
A lot of people overtighten things that aren't critical - some of the things where i work get tightened till they strip then backed off a quarter - would think thy are holding the ships propellor on.
Yep over tightening and over greasing - esp food machinery with food grease (sticky) are two of my pet hates

[KiwiBacon]

Yep over tightening and over greasing - esp food machinery with food grease (sticky) are two of my pet hates

Same here. I worked in a lot of bike shops when I was younger. Some bike mechanics would use 1/4 of a tub of grease when assembling a bike. Not only did it make a huge mess, they had to overtighten all the clamps to stop handlebars etc twisting around.

[thehanko]

Using a torque wrench with a longer handle than my regular socket wrench might be messing with my brain and what i "think/feel" like might be the right tightness. who knows....time will tell i guess.

I reckon its all about the longer handle and brain not working it out.

I had brake calpiers come lose on me once, so got the torque wrench out for its first real use to get it correct, and i though nah thats b s its loose as, got my normal socket handle to try to check how tight it felt with the short handle and just about busted my o ring

but another thing to be aware of is asking the bloke standing beside the car (aka phil) to check what the torque should be in the manual and believeing he checked it correctly, hmm 45Nm just doesnt seem to be enough for a caliper. (he read the wrong bolt info it should be 123Nm) so yeah it felt real loose.