A different kind of stuck bolt....


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Old 05-15-21, 08:04 PM
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A different kind of stuck bolt....

Hey Gang

I was having a tough time deciding if this was one for this forum or the auto repair crew.

I'm restoring this old commercial dough mixer. I have the unit largely broken down ready for blasting and refinishing. I'm down to the last four bolts that I need to remove. Here's the problem.

The housing including the bowl lifter and strap locks are aluminum. The slot head screws/bolts are steel. I've used penetrating oil and impact drivers. These bolts wont budge. This thing was made in the 80's and those bolts haven't turned since.

I was thinking to use a drag link socket on a breaker bar but I'm afraid I might just shear the head off.

I'm also being told I can heat it but I'm not sure weather to heat the steel nut or the aluminum housing?

I also have no idea how much heat to add. I don't want to damage the housing. Replacement parts are not available for this thing. I'm not sure if I can melt any of this with a garden variety propane soldering torch.

If I do heat... do I allow it to full cool before attempting to remove it? And then how much force can one safely apply?

I'm thinking since this are steel bolts in an aluminum housing this is a case of galvanic corrosion but I can't find anything useful out there on how to free it up.

I'm hoping someone might have some clever suggestion as to how to free up these bolts without destroying anything?

Thanks all!





 
  #2  
Old 05-15-21, 08:40 PM
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My first thought would be to try using an impact screwdriver. This is the type that you hit with a hammer, and the blow from the hammer helps turn the bit. It's possible that might help knock them loose without stripping the heads.

Example:

https://www.homedepot.com/p/TEKTON-3...2905/205674679
 
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Old 05-15-21, 08:49 PM
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@XSleeper - I used that exact tool. That's what I was referring to as impact driver in my OP. None of them budged even after days of bathing in PB Blaster.

I CAN twist harder when the drag link socket arrives and I put a 2' breaker bar to it... the question is... should I? I've loosened some stuck bolts in my time but I've never come across anything quite like this...

I'm thinking at the core of this problem is dissimilar metal corrosion. I know it's something that can be prevented... but I don't know if it can be remedied.
 
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Old 05-15-21, 08:54 PM
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Yeah I can see how that would definitely be a problem. Reminds me of the thread a while back of the guy that couldn't get his garden hose apart... similar problem where dissimilar metals had welded themselves together, making it impossible to unscrew. You might need to go after them with a drill and easy out, to the point of completely drilling them out and retapping them if they just won't back out. Perfectly centering your initial hole is the key.
 
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Old 05-15-21, 09:11 PM
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@XSleeper - I would like to try some heat before I take the (more) nuclear option.

Do you know if a small handheld propane soldering torch will generate enough heat to distort or damage aluminum?

 
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Old 05-15-21, 09:16 PM
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The problem is that you can potentially melt the aluminum if you apply too much heat. I don't think it will help in this situation. It would be different if it was steel or cast iron, and you were dealing with rust.

Also, without knowing what is inside you could potentially melt any rubber, nylon, or plastic / electrical parts inside.
 
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Old 05-15-21, 09:28 PM
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I have a breakout diagram of the machine and the bowl lifter is now separated from the main unit. I'm literally dealing with 4 steel bolts... the two aluminum straps... one steel guide plate and the aluminum cradle. That's it. There's no exit hole on the other end of the bolt hole. It's a dead end.

Does propane without added oxy burn hotter than the melting point of aluminum? Searching, I'm seeing different answers to that question.

I'd hate to try and refinish this thing without properly disassembling the unit.

One other thing I just came across. I read where mixing equal parts acetone and synthetic automatic transmission fluid will make a penetrating oil better than anything, anywhere... so as to release different metal corrosion. Have you ever heard of this?
 
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Old 05-15-21, 09:31 PM
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No. I think if there was a concoction that worked better than the commonly available ones, someone would already be selling it.
 
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Old 05-15-21, 09:37 PM
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YouTube "acetone and ATF penetrating oil" and let me know what you think. It's pretty compelling.
 
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Old 05-15-21, 09:46 PM
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I'm thinking at the core of this problem is dissimilar metal corrosion.
That is probably the issue.

So whenever I am forced to use the smoke wrench, the process is to heat the fastener up until it's red hot which then expands breaking the bond which then allows it to be removed, typ works well.

The problem with penetrating fluids, when something is locked tight it's basically water tight so nothing can get into the joints, plus being a screw you can not get a lot of torque applied like a bolt!

Aluminum melts at a lower temp than steel but the point is not to heat the alum directly just heat up the bolts, allow to cool a bit and see if they come loose.

Worse case, assuming it's all apart, you could have them drilled out and re-tapped!.

 
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Old 05-15-21, 10:00 PM
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@Marq1 - How would one heat the screw "red hot" without frying the aluminum into which it's housed?
 
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Old 05-15-21, 10:13 PM
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Aluminum melts at 1200 degrees, a red hot bolt is only, yea only, 900 degrees so you have some margin.

I'd try several applications, heating for periods of time, cooling, applying torque!
 
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Old 05-15-21, 10:19 PM
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@Marq1 - Thanks... I'm going to try heat for sure. I'm just thinking I should wait until I get that drag link socket so I can at least get a decent grip on it. Anything without leverage seems pointless.
 
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Old 05-16-21, 02:04 AM
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Isn't the bowl support hollow underneath ?
You could lay the machine on it's side or back and spray the threads directly.

I have big soldering irons..... 200 and 300 watt American Beauties. I would put the tip right on the screw head. Unfortunately these big irons are not inexpensive and not easy to find locally.
Big ass irons
 
  #15  
Old 05-16-21, 05:44 AM
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If the parts are not replaceable I would not go with taking a chance with heat. Especially if this is not a technique you are experienced with. I would go with brute force with the impact tool hoping to break free the screw. If you snap the head off the screw then you can separate the parts and work on extracting the remainder with an easy out. Failing that, drill out and make new threads. Maybe it is more work this way but at least you are not risking ruining non replaceable parts by a heating error. Or, rethink whether you absolutely must separate these items.
 
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Old 05-16-21, 06:07 AM
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I'm no expert on this but, I do have some experience with some of the ideas here. Personally... and I will stress.. personally, I wouldn't even attempt to heat with a torch. In my opinion, its far too likely that your going to ruin your aluminum piece,
Like Clancy said, I'd try every possible brute force & every some kind of penetrating oil for days or even weeks before I put that kind of heat on that aluminum.
If worse comes to worse, knowing that you say parts are no longer available for that unit, if the bolt broke, twisted off or became so damaged that you had to drill & tap, I'd try to find a machine shop to make me another screw, then drill & tap that thing out. You can use one of the other 3 bolts to show the machine shop. Then you'd still have matching bolts.... or at least, bolt heads. Which wouldn't alter the appearance.

Again, just me.......
 
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Old 05-16-21, 06:55 AM
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Reminds me of the thread a while back of the guy that couldn't get his garden hose apart...
I think I was part of that thread.



I would suggest heating the bolt and at the same time trying to work it loose with both a rocking action (slightly loosening it then tightening it). Not so much force as to shear the head off.
 
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Old 05-16-21, 09:32 AM
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I think I could have done a better job illustrating. Check out these pics and the video link. The steel bolts are in a solid aluminum housing. There's no access to the other end and.


Back

Front

Underside


Video
https://streamable.com/ez7yse

Looking at it.... even if I could get the strap off one side I could make it work
 
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Old 05-16-21, 09:48 AM
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Now that you have the unit apart you can set it so the screw heads are facing up.
Much better chance for the rust dissolver to penetrate down to the threads.
Keep the are well saturated for a while.
 
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Old 05-16-21, 09:51 AM
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I would try using a torch on it. There is so much metal I doubt you'll do any damage but you may be able to expand the aluminum enough to break the "weld" between the two metals. Problem I see is getting a good solid torque with a slotted screwdriver. You could drill a hole in the screw head and use an easy out to get better grip on the screw.
 
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Old 05-16-21, 10:50 AM
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Someone recommended using equal parts automatic transmission fluid and acetone as penetrating fluid.

Any opinions on this?
 
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Old 05-16-21, 11:47 AM
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No. I doubt any home concocted mix would be any more effective than a commercial made one.
 
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Old 05-16-21, 01:42 PM
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Why do you feel the need to separate the pieces. That won't affect the operation. Other than trying for perfection and possibly wrecking it. If it ain't broke don't fix it. Can't you just clean it up as is? Who will know that it wasn't completely disassembled. And other than you who will care?
 
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Old 05-16-21, 01:46 PM
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I think 2John is right. Is there any real need to disassemble the plate?
 
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Old 05-16-21, 02:28 PM
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What about welding a nut to the flat of the screw? It will allow you to apply more torque than can be generated from a screw slot.
 
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Old 05-16-21, 04:48 PM
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2john02458 - I really wanted to properly disassemble the unit correctly for proper abrasive blasting and re coating....That said.... I have a feeling it's not going to happen.

beelzebob - I can actually get a good grip on that slotted head. Enough that I think I could shear the head off. So welding on a nut - while very doable - would likely just make it easier to rip the head off.

I just got back into the house from a good session of heating. I tried propane with no effect and then map with the same result.

(insert sad face here)

Gang.... I don't think I'm going to win this battle. Indeed, I could drill this out but as was pointed out here..... It's probably not worth it at this point. It would be the right thing to do IF I could get them off.... BUT I can't.... I believe at this point that anything more I do will be too high-risk.

I'm going to flush the thing in acetone to get as much crud out as I can ....then do a hot pressure wash. I guess I'll protect the chrome guide by masking as best I can and then blast and re-coat the aluminum around it.

Shame... I really thought the transmission was going to be the headache with this restore.... but that was a breeze. This machine runs like a dream now... It turns out these four stupid bolts are the only real thorns.....





 
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Old 05-16-21, 10:52 PM
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I tried propane with no effect and then map with the same result.
You need acetylene, those type of gas torches are ok for soldering or heating up sprinkler hoses to put fittings on but just don't produce enough heat to get that bolt "red" hot, and certainly not enough to melt that big chunk of heat conductive Aluminum despite the dire predictions!

If you were in the neighborhood and could bring it over, we'd get it out!
 
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Old 05-17-21, 07:10 AM
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I have a feeling that if I was in your neighborhood youíd be seeing a lot of me
 
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Old 05-17-21, 07:34 AM
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I feel your pain, but sometimes just good enough has to be good enough. And if you don't point it out only you will know.

It turns out these four stupid bolts are the only real thorns.....
Even the most beautiful roses have thorns.
 
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