Avoiding Galvanic Corrosion

[noenegdod]

That takes care of twisting.
But torque produces clamping force. What is the safe working limit of the female thread in aluminum terminal?
Unlike engine bolts, these have relatively short engagement.

Once you put something on top of stud to restrain it, can't use a socket extension with torque wrench.
Some of the applied torque is lost due to friction, which is increased by radial load. Less clamping force for same torque, but probably goes in the "error" bucket, isn't accounted for.

Yes, if you apply enough torque to the stud, you will pull it out of the terminal regardles of whether or not it is threaded in or epoxied in and I should clarify that I too had understood the 8nm to be the torque spec for the terminal bolts which is apparently not correct. Im not saying "do this and your gold" it is just an additional layer of caution/protection.

use a crow foot to work around the interference on top.

 

[noenegdod]

Is it stronger? I wouldn't count on that. But maybe true. Have an explanation?

I should also say, its a super easy one to test. Just drill and tap 2 holes into a piece of softer aluminum like a 3xxx series but even 5052. epoxy a stud in one and once cured stick a spacer over the stud, a washer and a nut and torque them both and see which one fails first. just make sure you get the same thread engagement and the hole is epoxied properly.

 

[Ampster]

I should also say, its a super easy one to test.

Good idea. So you would not recommend trying this on a perfectly good cell?

 

[noenegdod]

LOL. Im doing it to 16 perfectly good cells (but not pulling them out ) I have done this for thread repair and prevention numerous times in all a few different materials with good success. Have done it in thousands of concrete holes and it is by far the strongest (of course not applicable to this)

 

[Hedges]

Have done it in thousands of concrete holes and it is by far the strongest (of course not applicable to this)

Were you the contractor on The Big Dig?

Boston Tunnel Collapse Kills Newlywed

Governor Seeks To Oust Turnpike Chief After Falling Cement Crushes Woman

www.cbsnews.com

There is a difference between high early strength epoxy, and one that does not creep.
Tying foundations together is different from hanging weight, or resisting tension of a torqued connector.
(Not a problem when epoxying threads which haven't stripped, however.)

 

[noenegdod]

Were you the contractor on The Big Dig?

Boston Tunnel Collapse Kills Newlywed

Governor Seeks To Oust Turnpike Chief After Falling Cement Crushes Woman

www.cbsnews.com

There is a difference between high early strength epoxy, and one that does not creep.
Tying foundations together is different from hanging weight, or resisting tension of a torqued connector.
(Not a problem when epoxying threads which haven't stripped, however.)

Nope, not sure what the connection is. Doesn't say what kind of anchor system they used.
For sure, rapid cure epoxies are typically not desired for much of anything long term.
Never tied foundations together. The typical application was bolting beams/columns to concrete walls/floors, bolting sawmill and pulp mill equipment to the slab and installing handrail to concrete slabs and stairs . Every single one resisting tension of a torqued connector.

 

[Hedges]

"The collapse of the ceiling structure began with the simultaneous creep-type failure of several anchors embedded in epoxy in the tunnel's roof slab. Each of the panel's intersecting connection points consists of several individual bolts anchored into the roof slab concrete. The failure of a group of anchors set off a chain reaction which caused other adjacent connection groups to creep then fail, dropping 26 short tons (24,000 kg) of concrete to the roadway below."

Big Dig ceiling collapse - Wikipedia

en.wikipedia.org

I recall reading at the time the epoxy was selected for the job without consulting manufacturer. I think the epoxy performed to specifications, was not correct for the application.

 

[Luthj]

Don't use epoxy. Threadlocker is best. Neither will significantly change thread failure load.

It's easy to look up the max torque for 6mm aluminum fasteners. It is NOT 8nm!

 

[noenegdod]

Ok, I get it now. Ya, you gotta make sure you do your job right. I have been out of the trades for 15 yrs now and have been in dental (Denturist) ever since. Im constantly shocked at the unethical and unprofessional garbage I see some dentists try to (and often do) get away with (mainly because patient has no idea because there isnt 24000lbs falling on their head)

 

[noenegdod]

Don't use epoxy. Threadlocker is best. Neither will significantly change thread failure load.

It's easy to look up the max torque for 6mm aluminum fasteners. It is NOT 8nm!

Why not and why?

Saying "aluminum fasteners" is a Pretty broad statement. There is a huge number of alloys and from one end of the spectrum to the other is massive. Look up the torque spec for 7075 and then compare it to a 1xxx series aluminum.

 

[Hedges]

Ok, I get it now. Ya, you gotta make sure you do your job right. I have been out of the trades for 15 yrs now and have been in dental (Denturist) ever since. Im constantly shocked at the unethical and unprofessional garbage I see some dentists try to (and often do) get away with (mainly because patient has no idea because there isnt 24000lbs falling on their head)

Samuel? Is that you?

Pittsburgh Dentist Used Paper Clips for Patients' Root Canals

Information on the outbreak of Meningitis in 2012 in Pennsylvania that was linked by the CDC back to steroid injections.

www.meyersmedmal.com

 

[noenegdod]

Nope!
Have never seen anything that bad, yet.

 

[Luthj]

Why not and why?

Saying "aluminum fasteners" is a Pretty broad statement. There is a huge number of alloys and from one end of the spectrum to the other is massive. Look up the torque spec for 7075 and then compare it to a 1xxx series aluminum.

Epoxy removal is a pain mostly. If any hardens on the contact area it can be an issue.

Threadlocker is cheap and easier to remove if needed. It also won't cure on the exposed contact face. Galled stainless threads do happen, and having an epoxied stud could be challenge.

By aluminum I mean cast or 1000 series. Just pick the lowest common value.

 

[noenegdod]

Simply practicing a little and perfecting application prevents all that.

For sure, you dont ever want to have to remove an epoxied stud, that would be an issue.

Galled threads are a common issue when using stainless fasteners but typically only when both the male and female threads are stainless (lubricating threads helps but certainly not a cure). I have only had issues with galling when really cranking on stainless. At the <4 lbft these are supposed to see I doubt there would be an issue. If you use a carbon steel nut or better yet, just use carbon steel stud if corrosion isnt an issue, applying the stud will be a once in a lifetime exercise unless you drop the cell or short it out so dont do that.

Just did a quick search and most aluminum fasteners are 2024 by the looks of it. Asked the supplier a while ago what alloy the terminals are but have not had a response yet so who knows what the terminals are actually made of.

 

[Bob B]

Simply practicing a little and perfecting application prevents all that.

For sure, you dont ever want to have to remove an epoxied stud, that would be an issue.

Galled threads are a common issue when using stainless fasteners but typically only when both the male and female threads are stainless (lubricating threads helps but certainly not a cure). I have only had issues with galling when really cranking on stainless. At the <4 lbft these are supposed to see I doubt there would be an issue. If you use a carbon steel nut or better yet, just use carbon steel stud if corrosion isnt an issue, applying the stud will be a once in a lifetime exercise unless you drop the cell or short it out so dont do that.

Just did a quick search and most aluminum fasteners are 2024 by the looks of it. Asked the supplier a while ago what alloy the terminals are but have not had a response yet so who knows what the terminals are actually made of.

It seems to me that getting the stud epoxied in without compromising the top of the cell's pad would be difficult. Seems like it would be impossible to fully fill the stud thread without some squeezing out on top of the cell.

Please epoxy yours and make a video of your technique for us.

 

[noenegdod]

It seems to me that getting the stud epoxied in without compromising the top of the cell's pad would be difficult. Seems like it would be impossible to fully fill the stud thread without some squeezing out on top of the cell.

Please epoxy yours and make a video of your technique for us.

I will! The most important part to keep the top clean is the volume which will be hard to show in a video, that will take some practice. I am considering drilling each stud with a vent hole and then applying epoxy to the first 2 or 3 female threads and then to the first male thread. Air will vent out the hole. If not, a drop in the bottom and turn it down until it oozes up through the threads. Im planning to use JB weld so Im not sure if it will actually pass through the threads without considerable force so there is going to be a few tests.

 

[Hedges]

You just apply some epoxy inside the female thread, not on the male thread. Then none gets on face of the terminal.
But even if it did you would just wipe off and clean with appropriate solvent before it cures.

"drilling each stud with a vent hole"
Hardware for use inside vacuum systems has such holes, so air isn't trapped to bleed out slowly.
It's bad enough dealing with gasses and H2O trapped in/on the metal without having a cavity that is almost sealed.

"oozes up through the threads"
Maybe the resin, if anything, and filler will be filtered out.
More likely you'll have made a hydraulic press.

Won't be any fun trying to drill a small hole through a stainless setscrew. Unless you have EDM?
Makes $3.42 each look like a bargain (6 mm x 25 mm)

Kurt J. Lesker Company

Enabling Technology for a Better World

www.lesker.com

Hey, it's cheaper than PEEK!

 

[noenegdod]

You just apply some epoxy inside the female thread, not on the male thread. Then none gets on face of the terminal.
But even if it did you would just wipe off and clean with appropriate solvent before it cures.

"drilling each stud with a vent hole"
Hardware for use inside vacuum systems has such holes, so air isn't trapped to bleed out slowly.
It's bad enough dealing with gasses and H2O trapped in/on the metal without having a cavity that is almost sealed.

"oozes up through the threads"
Maybe the resin, if anything, and filler will be filtered out.
More likely you'll have made a hydraulic press.

Won't be any fun trying to drill a small hole through a stainless setscrew. Unless you have EDM?
Makes $3.42 each look like a bargain (6 mm x 25 mm)

Kurt J. Lesker Company

Enabling Technology for a Better World

www.lesker.com

Hey, it's cheaper than PEEK!

On a lathe it only takes a minute or so to poke a small hole through a 1.25" stud and im not planning to use stainless either.

If you dont apply to the male threads, the first female threads can end up pretty dry by the time all of the male threads have passed by and picked up all they want. There ist a pretty good sized chamfer at the top of the hole as well so there is room for some overflow that wont affect the terminal surface.

The hydraulic press (hydro lock) thing is what Im concerned most about. It sounds like the bottom of the blind hole is pretty thin and I could see pushing it through it.

It would be pretty cool to get peek studs and hardware. I pay $15 each for tiny peek implant retention components so Id hate to see what a 6mm screw costs.

 

[Hedges]

M6-1 x 25, Philips, $6.37

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

You're right, and epoxy on the female means spare epoxy ends up at bottom of hole. Better to have it left on top.
Could lay a protective film, maybe painter's blue tape, over terminal.

I had a piston rusted/stuck in my CB77. Built an adapter from zerk to sparkplug thread. Filled cylinder with oil and used a grease gun to break piston free.
A colleague said he fills with oil, inserts a dowel, and smacks it with a hammer.
Sometimes hydro lock works to your benefit.

 

[Solarfun4jim]

I would have thought that by putting thread locker on the bottom of terminal hole, when you screw down into it the 'air pressure' plus thread locker mix would be forced up the threads(so long as you didnt put down too much)?