On 4/22/2011 7:51 PM, Califbill wrote:
I am doing some rebuild on my aluminum river jet boat. Going to weld
closed some old bolt holes in the gunnel and dash. What is a good
backing plate to prevent a big gob of aluminum slump on the backside,
where I can not get the grinder after I use the spool gun on the top. If
I had a TIG outfit, might be easier, but only a spool gun. 1/4" steel
plate? Stainless plate?

I have always been told stainless steel plate. Ernie on the welding
group would give you the best advice probably. Even though those are
relatively small welds you are going to on them for a while to fill the
holes, or going on and off them. One trick I have used to help control
heat is to put sopping wet rags behind my backing plate. You aluminum
still have to be cleaned and brushed and cleaned to be sure of getting a
good weld.