[avemg]

There are LED indicator lights that flash red when it detects a current drop. When the blade is not moving, you can touch it with your finger to see. In theory you could do this with whatever material you're going to cut. If you're cutting metal, it's pretty obvious that you need to disable the brake system. Usually where it's iffy is pressure treated lumber. Sometimes it'll trigger, sometimes not. Really depends on the moisture content of the wood and that can vary greatly. "testing" by touching the material to the blade with your hands on it might or might not indicate that the brake would fire. The points you're contacting could just not be that wet.

[vundercind]

Most cheap lumber I see these days has a lot of moisture in it, treated or not. I’m surprised this works at all for anything short of quite-nice stock.

[rrauenza]

Pressure treated wood is also soaked with copper azole, which I believe increases its conductivity.

[sidewndr46]

If you manage to cut metal with a table saw, you are a much braver person than I am

[_yb2s]

Aluminum cuts just like wood on a table saw. I wouldn't recommend trying to cut hard metals.

[sidewndr46]

With the right blade, I would think that is possible. When a piece of wood kicks back and hits me it leaves a bruise through the clothing I wear. If a piece of aluminum kicks back and hits me, I imagine it would be nearly fatal.

[_yb2s]

I've always just used a regular dull-ish wood blade... never died. Survivorship bias?

[avemg]

Iron and steel? Of course not, go get a cold saw for that. But it's no problem and very common to cut soft stuff like aluminum and copper on a table saw.