[ArkRoyal]

Hi All
I am new to this site and have been enjoying reading the wealth of information that is available on this site. A lot of good work has been done on all the articles.

But I read something that I believe can be dangerous, it's not a lot just one point, and felt I should post about it and give reasons and links that show why.

The information I am talking about is in http://www.myturbodiesel.com/1000q/multi/auto-mechanics-tips.htm And the section I am referring to is this:

NEVER use impact wrenches on lug nuts/bolts, also try wrapping the sockets in masking tape to avoid scratching wheels - First, wrapping sockets in masking tape when removing your wheel lug nuts will help them avoid scratches. NEVER use impact wrenches on lug nuts as this can damage the lug nuts and even crack the wheel. I always remove and install the lug nuts by hand, with a breaker bar and torque them by hand. Always use anti-seize on lug nuts. Excess torque will not only damage the wheel and lug nuts, but also may cause wheel vibration.

The author is absolutely correct about the effects of over torquing a wheel lug. But when he says to use anti-seize on the lugs he is in effect creating a condition of over torque. The torque specs are for dry and clean lugs not well lubricated lugs. Here is a link to a web site that will allow one to see the differences between a well lubricated bolt's torque and a dry and clean bolt:
http://www.efunda.com/designstandards/screws/calc_bolt_torque.cfm

I did a test just for an example. I used an SAE grade 8 bolt size 5/8 with extra fine thread. The torque for dry and clean is 220. The torque for well lubricated is 170. You can see that this is 50 foot pounds over torque. But it gets worse. Torque wrenches generally have plus or minus five percent tolerance. So it is very possible that when one thought the torque was 220 in actuality it was 231. So at this point we have an over torque situation of 61 foot pounds.

So the point is if the manufacture gives a torque specification for a dry and clean bolt use a dry and clean bolt with those torque specs. If you are going to change the conditions with anti-seize then do the home work needed to obtain the correct torque values.

 

[ArkRoyal]

I'm sorry if I made it seem like I was saying don't use some sort of lube on your lugs. This wasn't my point. The point I was trying to make was do the home work needed to reduce the torque to get do the job correctly. That is one of the reasons I gave the link to the site that give torque specs for bolts. It's not my site and I had nothing to do with putting it up but it is a very useful site. Anybody can get the measurements of their lugs and use that site to determine the correct torque.

I just think that over torquing, using the example I gave, by almost 35% is a lot of over torque. If you take your lugs off a lot, for what ever reason such as washing the rims, and you follow this way to torque them back you stretch the lugs a little each time. This can be a real problem for that time you are pushing it in the twistys an have your lugs fail and break. But hey you do get a nice white cross on the side of the road so maybe it's not all bad. ( That was a sick joke for those that don't know me.) I posted about this only because I thought there is a possibility that someone might get hurt. It won't happen right away but it can happen.

But this isn't just related to using anti-size. Here is a link to a case study of just the opposite problem caused from thread locker:http://www.boltscience.com/pages/casestdy.htm

Here is the important part:

During the design stage it was realised that the effect of the thread adhesive was to increase the thread friction.

So the torque values should increase when you use a thread locker. Unfortunately I don't have any information as to how much so your guess is as good as mine but at least we know it should be a little more.

I know this sounds like picking nits. But it's really not. I suspect it's one of the major reasons you here horror stories about guys doing a valve job or something and then have the head gasket blow out a few hundred miles latter. Or rods come apart because the builder put threadlocker on the rod bolts, causing an under torque situation, or using a lube on the rod bolts, causing an over torque situation.

One of the things I would really like to know but have found no information about is what is the effect of using a silicone adhesive on a bolt to prevent it from leaking when it goes into a water jacket. Generally these are very important bolts and I have no idea if it requires more torque or less.

Generally engines, and just about everything else, today doesn't have the generous tolerances that engines in the past had. In the past making it heavy was just way to keep it together. But today the use of special alloys and other ways to reduce weight and increase power to weight ratios put engines out on the edge with little room to play around with.

I don't want to appear as if I work with silk gloves on. I use an impact wrench to take off and put on my lugs. But when I put them on I turn the torque limiter down so it doesn't get close to the torque that I need. I then go back and torque by hand. This is very fast and I'm careful to not sling the gun around and damage things. I also use air tools when I work on just about any part of the cars I wrench on, butterfly impact and air ratchets are my fav. It's much faster but again when I need to get correct torque I turn the settings down enough so I can torque by hand.

 

[ArkRoyal]

Edited the article and included a disclaimer:http://www.myturbodiesel.com/1000q/multi/auto-mechanics-tips.htm

I am writing a basic guide for buying a torque wrench and basic torquing tips and I forgot that I cut a lot out of the mechanics tips article, I added back some tips. The torque wrench article has been a work in progress for a while. It is not up yet because I need to do a lot more research. I am not an engineer so I'm sure there'll be plenty of edits even after the article goes live!

I know that a lot of people buy cheap torque wrenches, they may work fine but I don't recommend them because they may lose accuracy with use or not even be accurate at all. There are also a few different types of torque wrenches and brands, hopefully this upcoming article will help give beginners a good view of what to look for.

I couldn't agree more about the torque wrench. Buy the best you can afford. When I was a youngster I made that mistake when I bought a cheap click type torque wrench. Well it just didn't click and I broke off the bold in the block. What a pain in the backside that was.