I have been making various efforts on a car I'm working on to remove underbody appointments, and have been having virtually no success. The car is aluminum, but the underbody components are attached primarily with steel bolts. The bolts are extremely rusty, and the aluminum is also pretty oxidized from being exposed to salt for many years. I've tried penetrating oil, which doesn't help; neither does hitting the bolt really hard. 8-)

It has been suggested that we heat the bolts with a torch, which should work - but I'm worried about damaging the aluminum. A few creative ways of heating and loosening the bolts without damaging the surrounding material have been suggested, including trying to hook up a welder. Does anyone have any ideas on how best to do this?

frank@gats.com

> I have been making various efforts on a car
> I'm working on to remove underbody
> appointments, and have been having virtually
> no success. The car is aluminum, but the
> underbody components are attached primarily
> with steel bolts. The bolts are extremely
> rusty, and the aluminum is also pretty
> oxidized from being exposed to salt for many
> years. I've tried penetrating oil, which
> doesn't help; neither does hitting the bolt
> really hard. 8-)

> It has been suggested that we heat the bolts
> with a torch, which should work - but I'm
> worried about damaging the aluminum. A few
> creative ways of heating and loosening the
> bolts without damaging the surrounding
> material have been suggested, including
> trying to hook up a welder. Does anyone have
> any ideas on how best to do this?

We're assuming you're talking about removing the bolts from the aluminum and not the nuts from the bolts.

When Ford first came out with aluminum heads for their engines (1920s?), they had the same problem, so they made a special hollow milling cutter which would fit around the studs and machine away the corrosion (and slightly enlarge the holes in the heads).

If this car of yours was made any time before about WWII, the aluminum itself may be decaying.

Both IRR 65 and LVT 1030 are made out of aluminum structural shapes, before proper alloying and anodizing had been figured out, and riveted together with steel rivets. Their fate is eventual disintegration through aluminum fatigue and crystalization acclereated by the electolysis caused by the dissimilar metals.

If you heat the bolts with a torch, you will probably ruin the aluminum because as you heat aluminum, it just sits there until suddenly turns liquid without warning. Try appling Kroil once a week for several months and then work the bolts back and forth with a box wrench or large impact gun until they break loose.

If you're trying to remove the nuts, try to locate a nut splitter, which is a screw device with a cold chisel edge that splits nuts cold. Unfortunately, these don't work in tight places.

If you do decide to use a torch to loosen the nuts, try heating the end of the bolt sticking out of the nut rather than the nut itself. This will cause the bolt to shrink slightly when it cools. Be careful of overheating the aluminum.

> If you do decide to use a torch to loosen
> the nuts, try heating the end of the bolt
> sticking out of the nut rather than the nut
> itself. This will cause the bolt to shrink
> slightly when it cools. Be careful of
> overheating the aluminum.

I believe that the bolt will expand when heated then shrink back to the original size on cooling. However this should still help in loosening the grip and breaking the corosion.

Robert@trainorders.com

> I believe that the bolt will expand when
> heated then shrink back to the original size
> on cooling. However this should still help
> in loosening the grip and breaking the
> corosion.

This is a good idea; it was one of the suggestions I got, but I wanted to know if anyone had a better idea. I appreciate the help. As for whether I want to remove the nuts from the bolts or the bolts from the aluminum, the answer is: both. The bolts hold on various pieces of equipment that I want to remove and rebuild, but I also want to replace the bolts themselves.

frank@gats.com

Okay, when all else fails you do it the HARD way.
cut the bolt off square, mark and center punch it, then step drill the center out of the bolt until you can collapse the remains, or if necessary, until you can retap one size larger (or with a helicoil.

> Okay, when all else fails you do it the HARD
> way.
> cut the bolt off square, mark and center
> punch it, then step drill the center out of
> the bolt until you can collapse the remains,
> or if necessary, until you can retap one
> size larger (or with a helicoil.

As far as heating the bolt for nut removal, the bolt expands, but the nut doesn't. Therefore, for the bolt to expand, it must elongate. When it cools, since it is now longer than it was, it shrinks in diameter slightly.

If you do the drill and collapse the thread thing, fix the hole with a helicoil becuase it will be stronger than the original. There are special shaped cold chisels (the point and the ofset of the shank) avaliable just for this purpose.

What grade bolts do you use for replacements?

> What grade bolts do you use for
> replacements?

Thanks for all the advice - it is greatly appreciated. As replacement bolts go, I don't know what we use - we haven't replaced any yet, as we haven't been able to remove even one! ...any suggestions?

frank@gats.com

ASTM A-193 B7 for the studs and ASTM A-194 2H for the nuts. For washers use standard pattern hardened.

Robert@trainorders.com

I'm not sure how this fits your situation, but I have had luck freeing some frozen bolts/nuts by heating, then shocking the heated metal with cold water. In many instances there is not room enough or a safe way (presence of oil/gas, etc.) to do this, however.

bobyar2001@yahoo.com

Sometimes this works very well if you drill the bolt hollow and spray the cold water down its length.

Dave

irondave@bellsouth.net

> ASTM A-193 B7 for the studs and ASTM A-194
> 2H for the nuts. For washers use standard
> pattern hardened.

What are the grade designations for these? Grade 2 (butter) is way too soft; obviously grade 8 is overkill. Grade 5?