A physicist's look at rusted bolts

[RG1911]

Since I wasn't clear on some of this, I found this most interesting. The following clear description is taken from "How to Dunk A Doughnut: The Science of Everyday Life," by Dr. Len Fisher. Chapter 3, "The Tao of Tools," is full of interesting information. (Dr. Fisher, originally from Australia, is a physicist with a fine sense of humor.)

Cheers, Richard
=====================

Undoing a bolt is a different story. It takes more force to undo even a clean, well-oiled bolt than it does to do one up, because the initial force to overcome friction and get the mating surfaces sliding (head and nut surfaces against the work, and two threads against each other) is greater than that required to keep them sliding, so wrenches will need to be held a little further out. When it comes to undoing a rusted bolt, the problem is not that the two threads are "stuck together" by the rust. The real problem is that, as iron turns to rust (a complex reaction product of iron, oxygen, and water) it expands, generating enormous pressures that increase the frictional forces between the threads. One can see how high the pressure can be by looking at a stone into which iron spikes have been driven. As the iron rusts, it is not uncommon for the pressures generated to be so high that the stone is split. Oil is of little use in reducing the frictional forces caused by rust. A better trick (if you have the time) is to use a weak acid such as vinegar to gradually penetrate and dissolve the rust. Alternatively, if the joint is accessible to heat, application of a propane torch will expand the bolt, the nut, and the gap in between to relieve some of the pressure.

Tightening bolts:

Stuart Burgess has made some interesting further points, which I quote here with permission:

1. A neat way to tighten a bolt is to heat it up first, and then do it up to hand tightness. When it cools down, it shortens, and becomes pretensioned.

2. Many screws are made of soft metals, and are easily damaged by hardened screwdrivers, and still more by hardened misusers of screwdrivers.

3. Spring washers are good at indicating the correct preload in screws and bolts.

[opos]

Among my "other" hobbies is the restoration and preservation of antique engines ...the old big flywheel engine..."hit and miss" style. Most are from 70 to over 100 years and when "found" the majority have been rusted stuck in one way or another...Guys in that hobby have probably tried everything known to mankind to free rusted up bolts, nuts, shafts, stuck pistons, rings, bearings, etc...

We use heat, Kroil, PB blaster, WD-40, and my favorite..Coke (the drinking kind!) An old saying with the old engines and with our old car hobby is that "rust never sleeps". I have a beautiful model 36, 3" square butt Smith that is from the 60's...it's a real nice one except for some minor "flecking" on the frame in one spot...I've gently worked that spot to try and at least hold it as it is but if I'm not on it all the time...it will still show a little minor increase..."rust never sleeps".

I'm old enough with failing eyes, etc that I don't take chances with the better firearms I own...if they need work and I'm at all concerned about my ability or tools..they go to a local smith..

For grins, a couple of pics (before and after) of a 3 hp hit and miss I restored a few years back....nothing turned or moved on this one and it ended up being a terrific runner.

[alamogunr]

A neighbor who happened to be a retired Air Force mechanic saw me fighting with an old Volkswagen bug muffler many years ago. He recommended an eyedropper with ammonia. If you ever replaced the muffler on those old bugs you know how they would rust out in less than 2 years. The bolts were even rustier than the muffler. It really worked. You just didn't want to be under the car when dripping ammonia on the fastener.

I never knew about vinegar and my opportunities to remove rusted bolts are few these days but I will remember this.

[John Boy]

For small parts to remove rust, they go in the rotary tumbler with the case burnshing solution - plastic media and a squirt of Dawn ...



To break the rust on bolts: a 50-50 mix of ATF and acetone

[mazo kid]

This from an old aircraft mechanic......Oil of Wintergreen!

[Hardcast416taylor]

Some advice I was given by a gunsmith many years back about how tight to tighten either a screw or bolt. Tighten it snug tight, but never `Farmer tight`(tighten till you hear a click/squeak noise) a `cheater bar` will be required to loosen it up again.Robert

[rondog]

I always torque things to "two ughs and a grunt"......

[Petrol & Powder]

I worked with a guy that routinely tightened things "as far as they would go and then a little bit more" ! He spent a lot of time fixing things that he was fixing.

[Petrol & Powder]

Among my "other" hobbies is the restoration and preservation of antique engines ...the old big flywheel engine..."hit and miss" style. Most are from 70 to over 100 years and when "found" the majority have been rusted stuck in one way or another...Guys in that hobby have probably tried everything known to mankind to free rusted up bolts, nuts, shafts, stuck pistons, rings, bearings, etc...

We use heat, Kroil, PB blaster, WD-40, and my favorite..Coke (the drinking kind!) An old saying with the old engines and with our old car hobby is that "rust never sleeps". I have a beautiful model 36, 3" square butt Smith that is from the 60's...it's a real nice one except for some minor "flecking" on the frame in one spot...I've gently worked that spot to try and at least hold it as it is but if I'm not on it all the time...it will still show a little minor increase..."rust never sleeps".

I'm old enough with failing eyes, etc that I don't take chances with the better firearms I own...if they need work and I'm at all concerned about my ability or tools..they go to a local smith..

For grins, a couple of pics (before and after) of a 3 hp hit and miss I restored a few years back....nothing turned or moved on this one and it ended up being a terrific runner.

OPOS, That is SUPER cool !!!!

[bubba.50]

I worked with a guy that routinely tightened things "as far as they would go and then a little bit more" ! He spent a lot of time fixing things that he was fixing.

my brother 'Horsefly' was a pretty good mechanic who is notorious for not knowin' his own strength when it came to tightenin' bolts. I guess he's probably wrung off a metric ton of them in his life. as his brother-in-law said one time, "I'd let Horsefly take anything off my car but, I wouldn't let him put anything on it."

[bubba.50]

I had a 1932 Harley-Davidson motor that had been used at a marina to anchor a buoy for decades. as you can guess nothin' would move on it. put it in a tub full of ATF & kerosene for a week or two & the bolts loosened up like it was just assembled.

[joatmon]

WoW John Boy gotta get me some of that!!
Aaron

[PtMD989]

My old vo-tech teacher used to tell us if we didn't know what the torque specs were. Just torque it down till it snaps then back it off a half a turn.


Sent from my iPhone using Tapatalk

[454PB]

My other hobby is riding and wrenching my Goldwing motorcycle. I've read lots of problems with the lug bolts shearing off the back wheel posted by others, and it's almost always caused by the use of anti-seize compound. Torque settings are always done with a clean, dry bolt. The guys having problems coat the studs with anti-seize and then torque to 80 ft. pounds. This results in a 30% over torque.

[ghh3rd]

About a year ago I decided to take apart and clean up the large vice that my father left me. It worked Ok, I just wanted to clean it up and paint it. Naturally everything except for one large bolt came apart. I tried soaking it with Kroil, and anything else I could think of for long periods and even heated it somewhat to no avail. I've moved since, and it's still in pieces in a printer paper box waiting for me to try again... someday.

Perhaps one of the methods suggested here will work.

[TCLouis]

I have a gun I have had soaking in kerosene for MANY MONTHS and still have the magazine stuck in it.

This week I will wash it off, find a plastic container and dump in some vinegar.

[oldracer]

I learned when I got my first car, a 1952 Chevy in 1963, that it was best to try and find torque specs for whatever you were working on. This has helped me well from small watch internals to tightening head hold down bolts on reactor pressure vessels. Those by the way are "stretched" with a hydraulic puller to about 1.5 million pounds pressure then turned finger tight. They are lubed with a mixture of alcohol/graphic dust. Anyways one of the weirdest I found were the lower suspension arms on new Chevys as you tighten them to a torque value (?) THEN turn another 180 degrees!
John

[Bulldogger]

Anyways one of the weirdest I found were the lower suspension arms on new Chevys as you tighten them to a torque value (?) THEN turn another 180 degrees!
John

I recently learned about this. In the case of my 1987 GM 6.2L diesel, it was a technique called Torque to Yield, and is meant for one-time-use bolts. The head bolts on my motor are this type. I've been told that GM discontinued this practice, but I'm sure others still use it. The bolts cannot be reused, as they have been pushed past their yield point. Apparently, someone thought it was a good idea for a while. I haven't researched why though.
BDGR

[Petrol & Powder]

I remember an engine builder that I knew using connecting rod bolts ONE time. They would set up the bearings and rod caps with old bolts and get the clearance set with a torque wrench and plasti-gage. If they couldn't get the clearance tight enough, they would machine just a hair off the end cap. When they got it right, the old bolts came out and were tossed. New rod bolts would be measured and installed. Those would be tightened until they stretched a certain amount. (verified with a jig and a dial indicator). The guy told me that a torque wrench was useless at that point and that the amount that the bolt stretched was the true indicator of clamping force. It had to be a virgin bolt that had never been tightened.

[TexasGrunt]

I have a gun I have had soaking in kerosene for MANY MONTHS and still have the magazine stuck in it.

This week I will wash it off, find a plastic container and dump in some vinegar.

Hope it's not blued.