Question about bolts

Hello

I have a question about bolts. I understand that there's different straight, sizes, pitch and torque rating. So my question is do torque rating match bolt sizes mabe not pitch but overall size? For an example. If a bolt needs to be torqued to 13 fbls does that actually mean it a 8m, or is there cases where there different size bolts with the same torque specs? I have the feeling there is, but not sure. I understand the torque specs are just the amount of pressure on the bolt, but still? There's a section in my manual on it but doesn't really answer that question. So I feel I still have to kinda guess.

 

the torque rating of any given bolt is a combination of it's material makeup, grade rating, thread style, mating surface material type, and tool attachment method (phillips and square drives are intended to cam-out near the complete torque rating, where standard bolts are not).

 

By cam-out do you mean strip, brake?

 

somewhat. it's also part of the design for assembly lines to prevent over-tightening.

 

If I understand your question which is do bolt torques from a vehicle manufactures line up with the max torque a bolt of that size, pitch, grade? The answer is no.

On some heavy equipment like CAT's that is the case from what i've been told,meaning any grade 10.8 bolt with a 16mm diameter and 1.75mm pitch will get torqued to x. For automotive purposes though thats not the case. Torque is dependant on the application, not just the bolt spec.

 

I will ask this a different way. What I ment was. Is there cases where there bigger bolts than needed with lower torque values when what it actually for. Loose torque on giant bolt. I guess strength comes in to play at that point.

 

I went down this rabbit hole once.

The good news is, the correct torque can be within a range for "most" applications.
Which is what what most charts list, the median "range".

The important part is knowing what grade bolt you are working with.
The bolt and the "nut" (part the bolt goes into) need to be the same grade. Or as close to the same grade as you can get.

Trust me on this. You don't want to over think it.
It will make your head hurt.


To answer your question. Bigger bolt = Less torque. YES, there are cases.
Take a look at the chart below.
Look at the 4T 14mm. It's listed at 55 ft/lbs
Now look at the 10T 10mm listed at 58 ft/lbs

 

Yes, example being calliper bolts on a Tacoma are around 70ft-lbs or something like that, meanwhile a chev truck's caliper bolts are the same size and grade yet get torqued to 140ft-lbs.

Or another example is older Camaro's. Same wheel studs but green nuts torqued to 110ft-lbs, blue torqued to 140ft-lbs until they scrapped the colours and they all got torqued to 140.

Last example is older duramax oil drain bolts. Rubber washer was 18ft-lbs, copper washer was 62ft-lbs. same oil pans and if you had to replace the bolt you would only be able to get one with a rubber washer. If you torqued the copper washer'd plug to anything less than 62ft-lbs it would leak.

 

Thanks that make sense. My next question is are most of the bolts on a 1st Gen tacoma 1.25 or 1.5 pitch when talking about the engine and trans. I'm kinda wondering From the graph

 

Dependent on application so you dont fuck up the mating pieces (dont overtighten it), but usually where Ive seen or experienced the fuck up is by having a shitty grade bolt. The cheap chinesium shit you mostly get from HD/Lowes or is a spare from something you ordered from Amazon is trash quality

 

Most 6mm-12mm are 1.25
14mm+ are 1.5mm

Now, let me throw you a curve.
The lug nuts are 12mm x 1.5


See........You don't want to go down this rabbit hole........

 

OK. I won't. I thought as it as a better way that to ask for certain bolts. I'm missing a few bolts and nuts, But there nothing really in the manual about actual bolt sizes, instead there's character and torque. Nothing on size for application. But I had fun with it for a little bit.

 

You’ll only find 8.8 or 10.9 in most hardware stores. (Strength)
Most commonly used are 8.8 for not critical fasteners (water pump, alternator, starter, pulleys)
And 10.9 for critical components. Like suspension, steering, brakes, frame components.

 

Thanks, I'm hoping for a better outcome next time I go to B&C. I went there looking and failed. I will take these into consideration. I know it's not a straight forward topic now. But hey, I tried. I hope these posts help someone if there reading this.