SS bolts in aluminum

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SIBERNUT

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Tried a search. Don't see anything here on how to get the dang things out. For maximum fun the heads are Allen , small, and recessed, threads into aluminum casting. Read a bunch of stuff says use heat after penetrating juice.
Well, if heat is good I'm tempted to stick the anode of my buzz box into the Allen & give it a good tickle. Good news- not in anything critical and part not attached to boat.
 
You want to heat the metal around the screw, not the screw. This will cause the hole to enlarge away from the screw causing the bond to be broken.
 
Greetings,
Mr. S. Mr. HC is correct. Heat the metal around the screw. Aluminum expands much more than steel and careful application of heat from a torch should loosen things up. You might also try an impact driver or an impact drill with the appropriate Allen bit after heating.


iu
 
Do not try to remove the bolt right away. Heat area , after it cools down a bit , use penetrating fluid. I like thrust .you don’t want it to smoke. After it’s completely cool do it again. No less than 3 times. Then attempt to extract.
 
Insert an bit into the bolt and give it about 25 taps with a hammer, that's how I get them loose.

Mvg,

Pascal.
 
We had an outboard repair shop in my store. The mechanic and I were friends and I learned a lot from him. Stainless bolts stuck in aluminum were an everyday occurrence. He referred to his torch as his fire wrench. When he reassembled the engine he would coat the threads with Permatex #3 Aviation Gasket Sealant. Next time he serviced that engine the bolts were easy to remove.
 
TKS guys. But heat can expand the metal in all directions, even around the bolt. I have a hot wrench & will try that 1st, let it cool, etc.
 
Well the expansion and contraction may break it loose enough to allow some corrosion inhibitor like PB Blaster to get inside the connection. I always use Tef Gel when I am screwing into aluminum. It helps get the screw out when needed.
 
I concur with all that has been said above regarding heating around bolt, not the bolt itself, and use of PB Blaster, etc. but will add one more tip:

When trying to remove anything stuck, alternate between force in the removal direction (counterclockwise) and force in the re-tighten direction (clockwise).
While that may seem counterintuitive the point is to try to break loose the corrosion between the two dissimilar metals.

Often working it back and forth in both directions will accomplish that faster.
Of course once you feel something give you can proceed in the removal direction.
 
Most all good advice...may need to try it all multiple times.

One of my bosses loved to use stainless in aluminum and I wound up helping to maintain a small fleet of commercial boats. he also used the Permatex trick, only worked to a point to prevent the next time.

If the bolts are less than 1/4 inch and have welded themselves inside of the aluminum....good luck and be patient.... all too often I had deadlines and many, many smaller bolts broke.
 
When trying to remove anything stuck, alternate between force in the removal direction (counterclockwise) and force in the re-tighten direction (clockwise).
While that may seem counterintuitive the point is to try to break loose the corrosion between the two dissimilar metals.

This technique will reduce the risk of snapping off the head by only forcing in one direction.
Is also particularly useful when working exhaust manifolds or anything where extreme heat has baked fittings in place.
 
TKS guys. But heat can expand the metal in all directions, even around the bolt. I have a hot wrench & will try that 1st, let it cool, etc.

That is not an uncommon belief... but it is incorrect.

Holes in parts will NEVER shrink from heat. They will always expand.

The following explanation is not my answer. But it explains it very well so I'll post it.

Assuming the disc is uniform and isotropic (the same in different directions), the hole will expand in the same ratio as the metal. You can see this because the thermal expansion equation

dL=LαdT

applies to all lengths associated with the metal, including the circumference of the hole, since the edge of the hole is made out of metal. And if the circumference of the hole expands, so does the diameter.


Instead of a circular hole, let's think of a square hole. You can get a square hole two ways, you can cut it out of a complete sheet, or you can get one by cutting a sheet into 9 little squares and throwing away the center one. Since the 8 outer squares all get bigger when heat it, the inner square (the hole) also has to get bigger:


This is confusing to people because the primary experience they have with stuff getting larger when heated is by cooking. If you leave a hole in the middle of a cookie and cook it, yes, the cookie gets bigger and the hole gets smaller. But the reason for this is that the cookie isn't so solid. It's more like a liquid, it's deforming. And as Ilmari Karonen points out, the cookie sheet isn't expanding much so there are frictional forces at work.
 
All good advice here. I will add a bit more to the work it in both directions hint.

At the first sign that the bolt has turned a bit stop and go the other way. Just because it turned a bit does not mean it's ready to back all the way out. With each reversal of direction add a bit more penetrating fluid. Each time resistance to movement increases go the other way. It takes a long time and a lot of patience but greatly increases the odds of success.

My personal favorite penetrating oil is Kroil with silicone.
 
Greetings,
A home made penetrant that has been mentioned numerous times on TF is a mixture of ATF and acetone. I think the ratio is 50:50. I've tried this and it appears to be as good as any OTC stuff.
 
Hi Siber,
Patience is your friend.
We buy BG In-Force by the case and repeat the heating and soaking over several days with critical parts. Still not always successful. Have also drilled a very small hole perpendicular to the bolt to promote internal dispersion if there is enough material to do so.
 
Good luck. I tried to remove 1/4" bolts stainless bolts (actually socket head cap screws) from an aluminum kayak mount.

After breaking a couple while working on the boat, I moved to my company workshop, with a torch, a vise, lots of patience and penetrating fluid.

I had success on the first two, but on the final mount, the aluminum was galled to the threads such that when I removed the screws a portion of aluminum (female) thread came out with the screws.

Aluminum, stainless and saltwater are a bad combination.
 
Greetings,
A home made penetrant that has been mentioned numerous times on TF is a mixture of ATF and acetone. I think the ratio is 50:50. I've tried this and it appears to be as good as any OTC stuff.

I first read that 50:50 mix in Popular Mechanix a few years back...they said it beat all the commercial products for penetrating.
 
My son is a mechanic and when he uses heat to remove a stuck bolt, he dabs a crayon on the threads. The heat sucks the wax in between the threads and makes removal easy as it cools.
Time is money and that's the fastest way he's found.
 
I will add that while almost any substance used during re-assembly is better
than using nothing between the SS screw and AL, anti-sieze compound is best.
 
I will add that while almost any substance used during re-assembly is better
than using nothing between the SS screw and AL, anti-seize compound is best.

Hopefully anti-seize compatible with aluminum...believe copper based is death to aluminum as in you never paint aluminum with copper bottom paint.

Yet there is literature that copper ant-seize is fine with aluminum. I would still use some other formulation...especially around salty environments.
 
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Hopefully anti-seize compatible with aluminum...believe copper based is death to aluminum as in you never paint aluminum with copper bottom paint.

Yet there is literature that copper ant-seize is fine with aluminum. I would still use some other formulation...especially around salty environments.
I appreciate the subtle correction that probably went unnoticed by most readers. ;)

I must have at least 4 different anti-seize compounds - the non-copper-based ones
would be my first choice, too.
 
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Update. Allen head bolts all came out after application of the hot wrench. Interesting part is that the threads into the castings were not corroded. The heads only were corroded to the castings they were countersunk in.
 
On my sailing vessel Pegasus we had to remove 400+ stainless fasteners from an aluminum mast. We were doing all the things advised above such as heat, lubricants, etc. except for that given by MacG, and were struggling to get them out. Our Master rigger came along, smiled, and said try tightening them first which was counterintuitive. As MacG explains that breaks the chemical bond from the corrosion and in nine cases out of 10 they simply came free and unscrewed.
New fasteners had Tefgel or blue loktite applied to threads to insulate the two metals.
 
Tapping it with a small hammer or use an impact should work. IMO... Use Tef Gel on reassembly and they will come apart like they were new even after 10 yrs.
 
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Really depends on fastener size and type of head pattern, also quality of fastener and what the object it is in.

Small, cheap fasteners will easily be destroyed with little force applied.

So some of the techniques used and in some combinations as recommended may work, others would be a bad idea...it just depends.

The OP said the fasteners were small, had Allen heads and were in a casting...so any method involving a bit too much torque may not end well. Unfortunately, it's a best guess what is too much.
 
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My son is a mechanic and when he uses heat to remove a stuck bolt, he dabs a crayon on the threads. The heat sucks the wax in between the threads and makes removal easy as it cools.
Time is money and that's the fastest way he's found.

Yup gold bars right here! A and P buddy taught me that as iron head kicking brat.
 
Heat, hammer taps penrtrating oil and patience will win the day. Also, socket/impact wrench a good tool.
 

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