LocostUSA.com

Interesting 5 minute video on torque and tensioning of bolts and how not to use rusty bolts or improve your rusty bolt.

Al


http://blog.hemmings.com/index.php/2013/03/15/tech-101-nuts-and-bolts-nuts-and-bolts/?refer=news

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Super Seven 3.4

Interesting ..... and reassuring. Despite recommendations to the contrary from every mechanic I have ever asked, I put a wee dab of never-seize on my wheel studs before applying the nuts. This supports the practice: after all, who cares if the nuts are torqued, but the wheel is loose, or nearly so?

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Warren
Isuzu Pickup/SR20DE, +401 COLD frame
Build Log: viewtopic.php?f=35&t=11601

Engine assembly instructions typically specify the thread lubricant corresponding to the specified torque. So if engine oil is specified, anti-seize will provide a lower friction coefficient and less torque is required. I remember it being about 10-15% less torque required.

For wheel bolts or lugs, I usually go to specified torque with anti-seize for a little margin; probably well within the allowable capacity.

Very interesting. I would assume that besides rust, all debris in the threads would have the same practical effect as the rust on their job site examples. I've always wire brushed bolts before returning them to their place, but I thought "dry" was OK. It looks like adding a little lube first would be a good thing.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

Bolts are interesting and impressive things. Imagine the 50,000 lbs. he's talking about is spread over the area of those threads.

I remember 30 years ago watching my race mechanic working on an engine, a fancier one than what's in my race car. He was measuring the length of each bolt very carefully with a micrometer. Then as he torqued it down, he measured again. The final judgement on the torque was given by the stretch of the bolt, not what the torque wrench was saying. In this case he was having trouble with one bolt and that's why I remember this, I think he had to make a call to Cosworth. It only takes one bad connecting rod bolt to cause a rapid disassembly event.

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Marcus Barrow - Car9 an open design community supported sports car for home builders!
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I would caution against putting lube on automotive fasteners. Except for the occasional cylinder head bolt etc, modern automotive fasteners are intended for "dry-torquing". Applying lube will massively increase the tension on the bolt (as shown in the video). The torque specifications do take into account the difference between dry and wet torque, and many automotive bolts/threads will immediately fail if you wet-torque to the dry-torque spec. Wheel studs on many cars cannot handle the higher tension either, and will be quickly damaged. I see a lot of cars with anti-seize on the wheel studs, and these same cars often have damaged threads.

Really that video mostly shows the difference between dry and wet torquing. The rust is a smaller matter. I would suggest spending more time cleaning the mating surfaces of components than most people do. Dirt/corrosion will compact, then wash away over time causing the clamping force to be reduced.

Also on a related note, these thread chasers are great! Probably one of the best tools I have ever bought. They will clean bolts, and save your butt if you have a damaged thread. They also roll the damaged thread back into place rather than cutting it off like a tap/die would.
http://www.langtools.com/sku-972-40-pc- ... torer-kit/
Mine is a Snap-on variant, but pretty sure that is the manufacturer of the kit.

Cheers.

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Build log: viewtopic.php?t=9291

I have generally use my tap and die set for cleaning and restoring threads, but that kit looks like a nice low cost option.

Al

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Super Seven 3.4

Yeah, the biggest difference is the tap/die will cut and remove metal, where the thread-chaser will roll threads back into place. The thread files work well too, if a bit slow. I've used them on CV axles a few times where the nuts damage the threads on the way off.

I use my kit several times a week in a high-volume shop; often to prevent nuts from packing-up on dirty threads before removing them (tie-rod nuts etc).

Cheers.

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Build log: viewtopic.php?t=9291

Here is a chart which shows dry VS wet torque.
http://www.spaenaur.com/pdf/sectionD/D48.pdf

For example, a grade 5 1/2" 20tpi bolt (typical wheel stud) dry torque is 90ft/lbs. It's wet torque is only 65ft/lbs.

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Build log: viewtopic.php?t=9291

When validating troque spec's on pre-production vehicles you even have to test for different types of painted surfaces, and if the surface is painted, or coated twice, once by a tear 2 supplier and a 2nd time by a tear 1 supplier it will some time changes the spec by more the 20%. DaveW

@C10CoryM
Thanks for that specific info on dry verses wet torquing.

You'd think screw thread stuff would be simple and well-understood, but it's actually pretty sophisticated in a number of respects. Having just recently gone through the exercise of learning about thread percentage for some drilling and tapping I was doing.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

Attention Jon- I was about to do this for you, but Cory beat me to it. You may be into yield territory, being 30% high.

You guys have forced me to dig a little deeper into this topic and think about my habit (I hate when I have to think, I'm retired dammit).

It not easy finding specs on auto lugs, but I'm fairly certain the Porsche lugs are DIN/ISO 898, Grade 10.9. Threads are M14 x 1.5. Porsche specified torque is 96 ft-lb or 130Nm. If I use the K values of .2 to .15, dry to lube; my actual factored torque would be 173 Nm. From another table from the web, yield torque is 184 Nm on these fasteners. Pretty close.

But, if I look at the lug configuration, there is an integral "washer" that seats against the alloy wheel and the lug bolt head. This protects the wheel from galling from the steel lug and provides a friction surface which provides the majority of tightening torque load (threads provide smaller portion).

Lesson learned for me (YMMV). Thread lube OK. Clean but dry friction surface to better control realized torque without risk of over tightening.

Enough thinking for the day, back to French polishing a guitar.

The video is about structural bolts for buildings, bridges and similar (ASTM A325, A409, etc.). These specs and the video cover bolts greater than 1/2" diameter and are not necessarily for automotive applications.

This is a whole different world from "mechanical" bolting typically specified in SAE, ASME, etc.