On Sat, 2 May 2009 18:49:38 -0700 (PDT), bob haller wrote:

On May 2, 9:43?pm, "MiamiCuse" wrote:
I need to cut a 3" cast iron vent pipe to tie to a new PVC vent.

I am using a Milwaukee sawzall with a metal blade and it kept skidding and
wouldn't start the cut at the right place. ?I then used a 4-1/2" angle
grinder with a metal blade and cut a little notch and now I can engage with
the sawzall without skidding.

However after 15 minutes of cut I don't think I am making a significant dent
at all.

I used the same sawzall and cut through copper and EMT electrical conduits
like knife through butter. ?But this CI pipe I am not making any progress.

I can't use the angle grinder there is simply not enough room around it.

I went to HD and they recommended a "grit iron" blade. ?Got that and it
seems to cut a little bit, but again after 15 minutes, I am not even 10%
through the pipe. ?The way I am going it would take 10 hours.

I remember seeing another blade named "ugly metal blade" I wonder if that
would be better.

Is there a better way to do this?

I know a chain cutter may be used, but I want to avoid it. ?Part of the
reason I am cutting this is because the lower section was cut by a plumber
who used a chain cutter but created a vertical crack line and now I am
trying to cut away all the damaged section.

Thanks,

MC

In the metalworking/machining trade, cast iron is not THAT hard. It does,
however produce no "chips" when being cut. Rather, it's a powdery residue that
clogs saw teeth and drill flutes. I'd select a bi-metal (high speed steel
teeth) sawzall blade with about 10 teeth per inch and use a lubricant such as
kerosene to keep the teeth flushed out. Cast iron can be cut dry, but, again,
keeping the saw teeth clear is important. I've had some success with candle wax
at times, too. But it requires a helper to hold the candle next to the blade
while it's sawing. Blasts of compressed air work, but everything within 10 feet
is gonna be black. Your face included