</font><font color="blue" class="small">( Bought a 9" rotary hacksaw blade (48 teeth) today to put in my circular saw . has anyone used them, are they good or bad, is there any special idiosyncrasies. cost $130 au. )</font>
Sounds like a cold saw, which is meant to run at low RPM, low feed rate, and used with coolant. Should last a long time if treated right. If you see sparks or blue chips, shut it down. It's self-destructing.