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Posted: Tue Oct 20, 2009 3:38 pm
by heathicus
JPG40504 wrote:I am surprised it works with cast iron! How hot???? Do not know how a cup warp would be thusly 'fixed'.
Do we have any materials experts aboard?? Please!
The fence on my jointer is aluminum. I don't really know "how hot" (and don't have a way to measure the temperature if I did) but I would love to know the answer. I heated it "too hot to touch" but didn't want to go much hotter than that on the first attempt. Maybe that was too much, maybe I should have gone hotter? I dunno. I can get a replacement fence, and since it was twisted anyway I figured I didn't have much to lose by trying.
But more information from someone who knows what they're talking about would be great!
Posted: Tue Oct 20, 2009 4:39 pm
by beeg
Aluminum melts at about 1220° F.
Posted: Tue Oct 20, 2009 7:57 pm
by JPG
WHEN did they start making the jointer fence out of ALUMINIUM?????
Posted: Tue Oct 20, 2009 8:35 pm
by heathicus
JPG40504 wrote:WHEN did they start making the jointer fence out of ALUMINIUM?????
My jointer is a 60's Craftsman.
Posted: Tue Oct 20, 2009 8:41 pm
by JPG
heathicus wrote:My jointer is a 60's Craftsman.
Do not recall THAT detail in the original 'post'!:D
http://www.shopsmith.net/forums/showpos ... stcount=19
Posted: Sun Jan 29, 2012 6:43 am
by Culprit
Heating metal and letting it slowly cool to relieve internal stresses (such as those caused by forcing the twisted fence back to straight) is called annealing. Many/most times air cooling is too fast; the piece is often submerged in sand and left to cool for days very slowly. This is most often done with iron and steel. Iron and steel are easier than Aluminum because they change colors as you heat them so that you don't go too far and end up cutting or melting them. Aluminum is harder because there is no visual indication of how close you're getting to the melting point.
One technique is to soot the Aluminum with a pure acetylene flame (oxygen completely off). A pure acetylene flame is very smokey/sooty. Heat the Aluminum till it is covered in the black soot. Then turn on a hotter oxy/acetylene flame and heat the Aluminum evenly. You can confidently/safely heat the Aluminum to the point that you burn off the soot without worrying about going to far and melting it. I'm not guaranteeing it will be hot enough to anneal the Aluminum, but it's as close as you can get at home without an oven purpose-built for annealing and cooling. Have a bucket or two of sand closeby to cover the piece and let it cool for a few days.
Yes, I realize this thread is a few years old, but it was just linked to for reference so I figured I would try to answer the question.
