This involves some dramatic surgery to the transformer. Here is one video about this, but you should search for others too.
The transformer primary will fry as the veggie oil will not be able to circulate through the windings to reach the core where the heat builds up most. proper oil cooled transformers have ducts in the windings to allow the oil to circulate to the centre of the winding. Your idea of oil cooling is good and it will work, but not on this level of overloading. Oh, the core will saturate magnetically, this will limit the output current.
If you have reduced the primary turns from 160 to 80, the core may saturate on the ac peaks and the primary draw perhaps 5 amps from the power line. The vegetable oil may boil after 5 minutes or so, but other damage or danger is unlikely. If the primary still has 300 turns or more the vegetable oil won't warm significantly, unless you short your new secondary. My guess is you do not have enough secondary turns to do spot welding for even microscopic assemblies.
If nobody answers I'll do it!
I'm trying to make a DIY spot welder without using a microwave oven transformer but a smaller transformer that is about 10 times smaller. I've removed about 80 turns of the primary and have been removing the secondary until it will be 0 turns. I'll then put in a thick cable wire about 3mm thick where the secondary use to be.
Now, if I wired this smaller transformer up to be operated with wall current like in this video:
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&sqi=2&ved=0CB0QtwIwAA&url=http%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3Dvrlvqib94xQ&ei=w5avU6CGDofi8gHswoGACQ&usg=AFQjCNHsm9gph0echtW44DgIbtzF03AJPg&bvm=bv.69837884,d.b2k
, sank the transformer in a small tub of vegetable oil as a coolant, and fired it up...will I still be alive? Will the house be alright? The transformer I have is about as big as 1.5 inch cubed.
