Remember these ??

There are certainly a few possibilities there, Trevor. I'm not convinced that filing in the lathe would generate sufficient heat to affect the metal but the oven offers possibilities I hadn't thought of.

Just as an aside, the weakest part of the Triang insulating is the flanged shoulder and when it perishes you can use a similar technique with "washers" that will stop the insulated side contacting the frame. I used this a few times with some club members bringing their old loved Triang numbers..

Hope this helps

Trevor