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Can someone quickly remind me? I am restoring an old fighting chair and need to remove frozen stainless steel bolts from an aluminum frame. Tried Aero-Kroil and PB Blaster to no avail. Have access to heat. Do I heat the bolt or the frame. Have concerns about getting the frame too hot and annealing(?) the aluminum. May have answered my own question there. Any help or other ideas is appreciated. Thanks...
I would be very careful not to heat the aluminum base. I would hit the bolt with a bit of heat let it cool down and hit with penetrating oil and see if you can work it free.
Bite the bullet and drill it out.SS and AL damn near welds itself together and heat on AL it touchy. Can you replace it if it melts or cracks?
The expansion coefficient of alum is greater than the SS bolt and it takes very little heat to do it. I would use an electric heat gun on the alum. Apply the heat around the entire circumference of the bolt but not on the bolt. When you think it's uniformly warmed up (alum), give the bolt head a hit with a hammer, but be careful not to bugger the allen head or slot in the process. It is probably a large allen head screw (like mine) so have the proper allen wrench with a length of pipe on it ready to go before it cools otherwise you may have to wait for it to completly cool and start over. It's a pita job but it should work. Years ago when I owned a firearms manufacturing company we routinely heat shrunk 4140 pre hardened chrome moly steel billets into 7075-T6 aircraft grade alum sleeves by cooling the steel with liquid nitrogen and heating the alum in an electric furnace to 700 deg F. The size differential was about 5 or 6 thousanths of an inch at ambiant temp. The temperature changes during the process was less than necessary to alter the temper and hardness of the metals.
Walt
Take an expendable (read EXPENDABLE) screw driver or allen wrench, whichever is needed for the fastener type, and make it red with a torch and immediately insert it into the fastener head and turn. The thermal shock should give you the edge you need. Have some PB blaster at the ready as well. Have a pipe or vice grips already attached to the wrench as seconds count. If that doesnt work, get a "pocket torch" from harbor frate and heat the bolt head directly. rebel
As noted, I heat the AL. This process is a daily thing if you work on old Brittbikes! The way you insert/remove bearings or any press-fit item in the AL cases is to heat the case/whatever in an oven to around 400 degrees. The bearings can dropped in/out. Same deal with bolts - just heat the AL with a propane torch or heat gun to the point where water sizzles on the AL and unscrew the bolt. It will be quite easy IF you get the temp up to the proper level. I have found that 350 in an oven was not enough but 375 did the job.
once you get it apart use a tap to clean the threads and before reassembly coat the bolt threads with 'tef-gel' from ultra safety systems to prevent the cold welding thing from happening again.
Thanks to all! The heating of the aluminum, accompanied by two days of PB Blaster seems to have done the trick. Only broke 1 of 4 bolts, and was able to drill and tap the broken one. Kinda tricky drilling the stainless bolt when the soft aluminum is so close. Worked out. Again, thanks...
Tef gel when u put them back in.
Quote:
Originally Posted by rsmith
Will do...