Separating Corroaded Brass and Aluminum

[DavidB]

I picked up an old surveying transit that is still on the tripod. The transit and tripod spent a while in a storage shed and corrosion has set in. I'm in the process of disassembling it to clean it up. My issue is that I cannot get the transit off the tripod. The transit has a large "nut" that threads onto the tripod base. The threads are 3.5"x8TPI from what I've read. I'll grab a picture of it later but the "nut" is circular and has some little cutouts to give you something to grab onto.

This "nut" is brass and the tripod is aluminum. They seem to have corroded together. I cannot get the thing loose. I've tried putting the tripod base in my vise and then using a strap wrench. The "nut" has some tabs that I've hammered against using a brass pin. I've tried PB Blaster, soaking the tripod base and nut in ATF/mineral spirits without luck. I tried wrapping the "nut" in a bicycle tire and then carefully using large Channellocks. I heated the brass some with a torch (Al expands faster than brass so I didn't expect this to work). I've got it sitting in my deep freeze currently. I'm doing my best not to tear up or mar the brass "nut" and have done well so far.

Does any one have any other ideas on getting this thing apart? Maybe there is a penetrant that would work better in this situation? I don't have a lot of experience working with brass.

Thanks,
David

 

[srmofo]

sounds like you need an adjustable spanner wrench to grab those "cutouts".

Vibration works well to loosen corrosion as well . Could try putting some wood against it and using an air hammer, although Im unsure what the vibration will do to the transit. Cant be good for it

Patience, heat cycles, and lots of lube will be key here. Ive found this New WD40 with Blue torch technology (whatever the hell that means) works pretty well on frozen up tierod ends. Those are always steel though.

Heating components up and then quenching them quickly with water also seems to work well to break the bond. Sometimes it takes a few heat/quench cycles.

 

[DavidB]

Hmm an adjustable spanner might work if I could find one large enough. This isn't mine, though I have the same model, but you can see the "nut" on the bottom on the pics in this page. http://www.mohaveinstrument.com/NewFiles/DW8300.html I've got the rest of the transit separated from the base so I'm not worried about damaging the rest of the transit through vibration. I've read that ammonia will dissolve aluminum oxide which what I believe the corrosion to be. I may try soaking it in there too.

 

[LifeLongWNYer]

I've had good luck getting things apart, for years, and with all kinds of metal, by using Kroil by Kano Laboratories. I don't think they sell in stores, whenever I need some I email them.

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[Luck-E1]

I use Gibbs Brand Penetrating Oil. That stuff works really good. Do a search for a distributor nearby.
Good luck!

 

[Kevin54]

Good luck getting it apart. I learned a long time ago about brass and aluminum together. I made some awesome dice valve stem caps. 6 months later, I had a low tire. They do not come apart without a hell of a fight. I finally had to get all new valve stems put in.

If possible, you might try heating the nut some to see if it will expand enough to break it loose, plus use a good penetrating oil.

 

[Kevin54]

You might also try, if possible to soak the two parts in a caustic solution to eat away the corrosion. Vinegar may work, or you might even try drain cleaner reduced down. But if left for too long will eat away at the aluminum.

 

[yhprum]

you may have to cut it through in one spot with a cutuff wheel to release it and get/make another nut if you cant free it up.

 

[Erampu]

Give a three year old a shot at it. They can take just about anything apart.

 

[rsanter]

Get a car of the freezing stuff that they use to shrink parts to put them together.
Hit it with that a few times to give the corrosion a shock and then try to take apart
The aluminum will shrink more than the brass

Bob

 

[sselander]

Get a car of the freezing stuff that they use to shrink parts to put them together.
Hit it with that a few times to give the corrosion a shock and then try to take apart
The aluminum will shrink more than the brass

Bob

CRC Freeze-Off, it is actually mentioned in my Mazda service manual

 

[raddksn]

Give a three year old a shot at it. They can take just about anything apart.

Love this one!

 

[V-10 Killer]

Give a three year old a shot at it. They can take just about anything apart.

Too funny, I can relate to that lol.
When I was that age, my aunt was babysitting me, but I managed to find a screwdriver when she wasn't looking, and proceeded to remove about half of her interior doorknobs before she caught me