On 6/1/2012 4:25 AM, Ed Huntress wrote:

Plus, the heat of friction introduced into the disk is distributed
*around* the entire disk, while the roughly equivalent heat of
friction in the work is concentrated at the spot you're cutting.



I've heard that, with aluminised corrugated sheets (I think that's what
we're talking about?), too much heat can damage the coating, to the
extent that its rust preventing action is compromised.
It's made me too nervous to use a friction cut, except for real
galvanised steel sheeting. Then, a steel circular saw blade mounted
backwards serves OK - something I learnt here.
Or as mentioned, friction cut an inch outside the finished line and trim
with hand snips.