Cast Aluminum

Cast Aluminum:

Alloy #5 works nicely on cast aluminum up to 3/16th". However, because of the varying degrees of cheap filler material in its composition, more heat is needed to make the rod flow than with tube or sheet aluminum. Consequently, you are very close to the sagging point of cast before alloy #5 begins working. The same is true of aluminum with a high magnesium content. So, we strongly suggest about an hour of concentrated practice.

Here are some helpful hints to get you up to speed quickly:

Ø Begin practicing on a small throw-away piece (thermostat housing or a chunk of bell housing).

Ø Be prepared to make some mistakes while learning.

Ø Always wear dark glasses when repairing any kind of aluminum with an oxy-acetylene torch because the acetylene and flux combine to give off yellow/orange color.

Ø Always use oxy-acetylene when repairing cast aluminum. Use a #2-#4 tip (practice with each) and a 1/4" blue flame. Crank the oxygen (much "hissing") at first.

Ø While holding fluxed rod at the ready, preheat beginning of repair area. Keep the heat in one place until skin of aluminum begins to "dimple" or change color. Bring fluxed rod in so it touches aluminum. Work tip of rod with flame.

Ø If the rod balls up upon touching aluminum, it means the cast is not yet hot enough to pull in the rod material, so take the rod away and do some more pre-heating.

Ø Reflux the rod. Bring it back in.

Ø When the rod begins to flow ("puddle" on cast aluminum), take the torch away and turn the oxygen down for greater control.

Ø Now pick up some more flux and come back in with the rod--then flame. Take a little deposit off rod and flow it out.

Ø Continue repeating these steps - melt flux and a little deposit off rod, flow deposit out, take heat away, reflux rod, melt flux and a little deposit off rod, flow out deposit, take flame away, reflux...and so on until repair is complete.

Ø Using a backing plate can help prevent sagging.

Ø If you are willing to do a bit of patient practicing, you can become a master cast aluminum repair person.

Ø Which means you will be a master at repairing virtually any kind of metal because cast/magnesium aluminum is the only metal that is even slightly difficult using Alloys #1, #5 or #6.

Ø All repairs are totally machinable (see Alloy #5 example page).

Ø Whenever repairing cast aluminum, be sure to use a snugly fitting malleable copper backing plate. Just clamp it in place until the repair is completed. This way, you can use plenty of heat without worrying about the cast sagging away. Simply build up again any spots that have dimpled.